**National Climatic Data Center**

**DATA DOCUMENTATION**

**FOR**

**DATA SET 3280 (DSI-3280)**

# Surface Airways Hourly

# 

**May 4, 2005**

National Climatic Data Center

151 Patton Ave.

Asheville, NC 28801-5001 USA

**Table of Contents**

[Topic Page Number]{.underline}

1\.
Abstract\...\...\...\...\...\...\...\...\...\...\...\...\...\...\...\...\...
3

2\. Element Names and Definitions**:**
\...\...\...\...\...\...\...\...\.... 4

3\. Start
Date\...\...\...\...\...\...\...\...\...\...\...\...\...\...\...\... 28

4\. Stop
Date\...\...\...\...\...\...\...\...\...\...\...\...\...\...\...\.... 28

5\.
Coverage\...\...\...\...\...\...\...\...\...\...\...\...\...\...\...\.....
28

6\. How to order
data\...\...\...\...\...\...\...\...\...\...\...\...\..... 28

7\. Archiving Data Center.
\...\...\...\...\...\...\...\...\...\...\..... 29

8\. Technical
Contact\...\...\...\...\...\...\...\...\...\...\...\...\..... 29

9\. Known Uncorrected Problems\...\...\...\...\...\...\...\...\...\.....
29

10\. Quality
Statement\...\...\...\...\...\...\...\...\...\...\...\...\..... 29

11\. Essential Companion Data Sets\...\...\...\...\...\...\...\...\.....
30

12\.
References\...\...\...\...\...\...\...\...\...\...\...\...\...\...\...\...
30

**1. [Abstract]{.underline}:** This global data set contains hourly or
3-hourly surface weather observations that are measured primarily at
major airports and military bases. Observations are made by trained
personnel or automated equipment that has been tested by the controlling
agency. The stations are usually fully instrumented and therefore record
a complete range of meteorological parameters. It must be noted that
NCDC has the observations from the time the station opened, but the
[NWS](http://www.nws.noaa.gov/) has the current data. Official surface
weather observation standards can be found in the [Federal
Meteorological
Handbook](http://www.nws.noaa.gov/oso/oso1/oso12/fmh1.htm). The
observations are generally recorded for the 24-hour period midnight to
midnight.

The major data variables and parameters are as follows: Record Type
(HLY), WBAN Identification Station number, Units of measurement
indicators, source codes, data quality flags, and element types: cloud
data, visibility data, wind data, temperature data, sky cover data,
relative humidity data, pressure data, and present weather data. Hourly
precipitation data are stored in the Hourly Precipitation Data file
DSI-3240.

The stations are located worldwide and are operated by the National
Weather Service (NWS), U.S. Air Force (Air Force Weather), U.S. Navy
(Navy Weather Detachments) and the Federal Aviation Administration
(FAA). The NWS and FAA sites are located in the contiguous U.S., Alaska,
Puerto Rico, Hawaii and other Pacific Islands. The Navy and Air Force
operate stations worldwide.

This digital data file primarily begins in the late 1940\'s. Much data
for earlier years are available in manuscript form. Beginning January 1,
1965, for most NWS stations and March 1, 1972, for most Naval Weather
Service stations, the digitizing of the airways observations was reduced
from 24 observations per day to 8 observations per day. These
observations, at 3-hourly intervals, coincided with the normal GMT
schedule of 00Z, 03Z, 06Z, etc. This means that the observations, keyed
in local standard time (LST) differ according to time zone. Beginning
with August 1981 data, 24 observations per day were again digitized for
most active stations. Through the years approximately 1,500 principal
stations have recorded observations in this program. In 1984 there were
just more than 370 active stations being processed for inclusion in the
digital database. In 2005, there were approximately 385 active stations
being processed. Surface airways hourly data were initially transferred
to punch cards beginning in the late 1940\'s to facilitate summarizing
climatological data. The late 1960s saw the transfer of punched cards to
magnetic tape. These TD-14 formats represented the digital file through
1983. In 1983, an element file structure was developed and processing of
airways hourly data was revised. This processing system became
operational in January 1984. Data are currently processed utilizing the
element file structure. The conversions of historical data included
gross data checks on the DSI-1440 data file. No edited values were
derived during the historical conversion but nondecodable data were
flagged.

Due to many special projects performed at NCDC and other Centers, 24
hourly observations may have been keyed for varying periods of time for
selected stations. Inventories must be consulted to determine the exact
period of record for each station. Beginning with the data for January
1984, the surface airways hourly observations were processed through a
completely revised system. Relying heavily on new computer editing
procedures, data are subjected to internal consistency checks, compared
against climatological limits.

In September 1992, the [Automated Surface Observing
System](http://205.156.54.206/asos/) (ASOS) was gradually implemented
for stations in this data set replacing the human observer. ASOS was
designed specifically to support aviation operations and forecast
activities. The automated system provides continuous minute‑by‑minute
observations which are then averaged into an hourly observation. The
capability does exist for a human observer to augment parts of an ASOS
observation. For example, a human observer may augment an ASOS
observation to include cloud conditions above 12,000 feet.

There are three main components to ASOS: 1) the Individual Weather
Sensors, 2) the Data Collection Package(s), and 3) the Acquisition
Control Unit. ASOS was designed primarily for aviation use. NWS
recognized that other users have become accustomed to data no longer
provided by ASOS or are provided in a different way. As a result,
significant changes have occurred in this data set for many previously
observed weather parameters. The user is advised to carefully read the
documentation for each desired weather element in order to ascertain any
possible data biases that may have been introduced in the historical
record as a result of ASOS.

On July 1, 1996, another significant change occurred, which involved the
operational transmission of hourly surface observations. On this date,
the United States implemented the International METAR transmission
format code, replacing the long-standing Surface Airways Observation
(SAO) code. The METAR code requires different format procedures for
transmitting basic weather observations. For example, cloud amounts are
transmitted in eights as opposed to tenths and temperature is
transmitted in Celsius as opposed to Fahrenheit. There are many other
differences, both major and minor. Again, the user is advised to
carefully read the documentation for each desired weather element in
order to ascertain any possible data biases that may have been
introduced in the historical record as a result of the METAR code
change.

Users must be aware that DS-3280 and DS-3283 are similar. The only
difference is that DS-3280 contains quality controlled data that has
been hand checked by personnel at the National Climatic Data Center.
DS-3283 only contains data that is automatically quality controlled,
therefore, it is considered to be "raw" data.

**2. [Element Names and Definitions]{.underline}:**

**Format**

+----------+------------+---------------------------------------------+
| *        | **         | **Description**                             |
| *Field** | Position** |                                             |
+----------+------------+---------------------------------------------+
| 001      | 001-003    | Record type                                 |
+----------+------------+---------------------------------------------+
| 002      | 004-011    | Station ID                                  |
+----------+------------+---------------------------------------------+
| 003      | 012-015    | Meteorological element type                 |
+----------+------------+---------------------------------------------+
| 004      | 016-017    | Met. Element measurement units code         |
+----------+------------+---------------------------------------------+
| 005      | 018-021    | Year                                        |
+----------+------------+---------------------------------------------+
| 006      | 022-023    | Month                                       |
+----------+------------+---------------------------------------------+
| 007      | 024        | Source code 1                               |
+----------+------------+---------------------------------------------+
| 008      | 025        | Source code 2                               |
+----------+------------+---------------------------------------------+
| 009      | 026-027    | Day of month                                |
+----------+------------+---------------------------------------------+
| 010      | 028-030    | Number of data portion groups that follow   |
+----------+------------+---------------------------------------------+
| 011      | 031-034    | Time of observation (hour)                  |
+----------+------------+---------------------------------------------+
| 012      | 035        | Sign of met. Value                          |
+----------+------------+---------------------------------------------+
| 013      | 036-040    | Value of met. Element                       |
+----------+------------+---------------------------------------------+
| 014      | 041        | Quality control flag 1                      |
+----------+------------+---------------------------------------------+
| 015      | 042        | Quality control flag 2                      |
+----------+------------+---------------------------------------------+
| (        | (043-054)  | Data groups in the same form as fields      |
| 016-020) |            |                                             |
|          |            | 011-015. Repeated as many times as needed   |
|          |            |                                             |
|          |            | to contain one day of record                |
+----------+------------+---------------------------------------------+
| (        | (055-066)  |                                             |
| 021-025) |            |                                             |
+----------+------------+---------------------------------------------+
| (        | (067-078)  |                                             |
| 026-030) |            |                                             |
+----------+------------+---------------------------------------------+
| (        | (          |                                             |
| 196-201) | 1219-1230) |                                             |
+----------+------------+---------------------------------------------+

**SPECIAL NOTES**

[CEILING HEIGHT]{.underline}

Ceiling was recorded in hundreds of feet above the ground to nearest 100
feet up to 5,000 feet, to nearest 500 feet from 5,000 to 10,000 feet, to
nearest 1,000 feet above that. The recording increments changed for
Automated Surface Observing System (ASOS) stations beginning in 1992.
ASOS stations report ceiling up to only 12,000 feet with a precision to
nearest 100 feet up to 5,000 feet, to nearest 200 feet between 5,000
feet and 10,000 feet, and to nearest 500 feet above 10,000 feet. Before
1949 Air Force stations recorded ceilings up to and including 20,000
feet, above which point the ceiling was classified as unlimited; Weather
Bureau and Navy stations recorded ceiling only up to and including 9,500
feet, above which point the ceiling was considered unlimited. Beginning
in 1949, ceiling was redefined to include the vertical visibility into
obscuring phenomena not classified as thin, that, in a summation with
all lower layers, covers 6/10 or more of the sky. Also at that time, all
limits to height of ceiling were removed, so that an unlimited ceiling
became simply less than 6/10 sky cover, not including thin obscuration.
Beginning June 1, 1951, ceiling heights were no longer established
solely on the basis of coverage. The ascribing of ceilings to thin
broken or thin overcast layers was eliminated. A layer became classified
as \"thin\" if the ratio of transparency to total coverage at that level
is 2 or more.

[SKY CONDITIONS AND CLOUD LAYERS]{.underline}

Many different coding practices on sky conditions and cloud layers
occurred throughout the years. The mid 1980 element format conversion
took into account all the different practices and converted all the
procedures into a common format. If one is interested in all the changes
in coding, please refer to WBAN Surface Observations Card Deck 144
documentation.

[DATSAV SOURCE DATA]{.underline}

Because of differences in Airways and METAR codes and the limited
information available on the telecommunicated source compared with
manuscript forms, DATSAV derived data contains less complete information
than otherwise available. Element conversions unique to METAR stations
are as follows:

> 1\. [Visibility]{.underline} - METAR codes are converted to Airways
> codes or the NCDC database. This conversion will cause 6-mile
> visibilities from METAR stations to be recorded as 7-mile
> visibilities. METAR code permits the transmission of a visibility of
> 9,000 meters without obstruction, while Airways requires a visibility
> of at least 7 miles without obstruction. The 9,000 meters is converted
> to 6 miles in the program and flagged because it is less than the
> 7-mile requirement. These 6-mile visibilities are changed to 7 miles
> so that these data will conform with the rest of the data in the data
> base. When \'CAVOK\' is found in the transmitted data, 7 miles with no
> obstructions is entered in the database.
>
> 2\. [Weather]{.underline} - Only the highest numbered weather code is
> transmitted. This causes all accompanying weather to be lost from the
> database. For example, the manuscript form might indicate moderate or
> heavy rain and snow showers mixed (code 84) with fog (code 45). Only
> code 84 will be transmitted and fog will be eliminated.
>
> 3\. [Clouds]{.underline} - Total sky and sky condition are not
> reported on telecommunicated data. Layer amounts are reported in
> eighths and converted to tenths. This conversion results in the loss
> of any entries of 2 or 7 tenths.
>
> 4\. [Ceiling]{.underline} - When \'CAVOK\' is found in the transmitted
> data, an unlimited ceiling is entered in the data base.
>
> 5\. [Temperature and Dew Point Temperature]{.underline} - These
> temperatures are given in Celsius on the forms, Kelvin on DATSAV,
> Celsius on intermediate output, and are stored in Fahrenheit in whole
> degrees in the data base. Rounding during conversions can cause a loss
> of accuracy of one degree.

[RECORD TYPE]{.underline}

The type of data stored in this record. Value is \"HLY\"). Each record
contains one day of hourly values.

[STATION-ID]{.underline}

Contains the WBAN Station Number. (Assigned by NCDC.) ID Range of values
= 00000000-00099999. Five digit station numbers are always right
justified and zero filled.

[METEOROLOGICAL ELEMENT-TYPE]{.underline}

The type of meteorological element stored in this record consisting of a
four character alpha. Range of values is listed below.

###### ALC\"x\"

DESCRIPTION: Sky condition in tenths and height per layer.

VALID TIMES: Used from 9/1992 thru current

STATION TYPES: ASOS and ASOS Augmented only

COMMENTS: This element began with the implementation of ASOS in
September 1992. The ASOS ceilometer provides data for a maximum of three
layers at or below 12,000 feet and does not distinguish between thin and
opaque cloud layers. ASOS sites augmented by a human observer can report
up to six layers of clouds and are not limited to 12,000 feet. Beginning
July 1, 1996 with the implementation of the METAR code, the element
ALC@x@ (tenths) was derived from the element ALM@x@ (eights).

The \"x\" indicates the layer where:

1 = The lowest layer

2 = The second layer

3 = The third layer

4 = The fourth layer (ASOS Augmented stations only)

5 = The fifth layer (ASOS Augmented stations only)

6 = The sixth layer (ASOS Augmented station only)

The DATA-VALUE portion of the record will appear as XXYYY where:

XX = The code for sky condition

YYY = The layer height in hundreds of feet.

[XX Code - Sky Condition]{.underline} (tenths)

00 = clear or less than .1 coverage

02 = scattered .1 to .5 coverage

04 = broken .6 to .9 coverage

06 = overcast 1.0 coverage

07 = obstruction 1.0 coverage

09 = unknown

NOTE: The XX code is the same used for element CLC\"x\" except that thin

layers and partial obscurations are not currently measured by ASOS.

[YYY Code - Layer Height]{.underline} (hundreds of feet)

000 = Clear conditions (with \>00\' code for XX)

999 = Unknown value (with \>09\' code for XX)

The NWS Automated Surface Observing System (ASOS) began gradual
implementation at weather stations in September 1992. Sky and ceiling
information are automatically derived from ceilometer data in the ASOS.
Except in the case of augmentation, sky and ceiling are no longer an
estimate of conditions from a human observer. The ASOS cloud height is
an estimate based on the heights of clouds detected every 30 seconds
during the previous 30 minutes (with the last 10 minutes of data double
weighted). The cloud amount (CLR, SCT, BKN, OVC) is derived from the
ratio of the number of possible hits. The ceilometer measures clouds at
or below 12,000 feet.

###### ALM\"x\"

DESCRIPTION: Sky condition in eights and height per layer.

VALID TIMES: Used from July 1, 1996 thru current

STATION TYPES: ASOS and ASOS Augmented only

COMMENTS: This element is only used for stations using the ASOS system
and begins in July 1996. The ASOS ceilometer provides data for a maximum
of three layers at or below 12,000 feet and does not distinguish between
thin and opaque cloud layers. ASOS sites augmented by a human observer
can report up to six layers of clouds and are not limited to 12,000
feet. The element ALC@x@ (tenths) was derived from the element ALM@x@
(eights).

The \"x\" indicates the layer where:

1 = The lowest layer

2 = The second layer

3 = The third layer

4 = The fourth layer (ASOS Augmented stations only)

5 = The fifth layer (ASOS Augmented stations only)

6 = The sixth layer (ASOS Augmented station only)

The DATA-VALUE portion of the record will appear as XXYYY where:

XX = The code for sky condition

YYY = The layer height in hundreds of feet.

[XX Code - Sky Condition]{.underline} (eights)

00 = Clear

01 = few scattered 1/8 to 2/8 coverage

02 = scattered 3/8 to 4/8 coverage

04 = broken 5/8 to 7/8 coverage

06 = overcast 8/8 coverage

07 = obscuration 8/8 coverage

09 = unknown

NOTE: This XX code is the same used for the element CLM\"x\", the MAPSO
station version of ALM@x@.

[YYY Code - Layer Height]{.underline} (hundreds of feet)

000 = Clear conditions (with \>00\' code for XX)

999 = Unknown value (with \>09\' code for XX)

The NWS Automated Surface Observing System (ASOS) began gradual
implementation at weather stations in September 1992. Sky and ceiling
information are automatically derived from ceilometer data in the ASOS.
Except in the case of augmentation, sky and ceiling are no longer an
estimate of conditions from a human observer. The ASOS cloud height is
an estimate based on the heights of clouds detected every 30 seconds
during the previous 30 minutes (with the last 10 minutes of data double
weighted). The cloud amount (CLR, SCT, BKN, OVC) is derived from the
ratio of the number of possible hits. The ceilometer measures clouds at
or below 12,000 feet.

###### ALTP

DESCRIPTION: Altimeter setting.

VALID TIMES: All stations begin on July 1, 1996; Navy stations begin in
September 1984

STATION TYPES: All stations (ASOS, ASOS Augmented, and human observer)

Range of values: 02700 to 03200

###### CC51

DESCRIPTION: The sky condition.

VALID TIMES: Prior to June 1951

STATION TYPES: Human observer stations only

COMMENTS: Old code not used since June 1951

DATA-VALUE will appear as 0XYYZ where:

X = Amount of higher layer

YY = Height of lowest scattered layer in hundreds of feet

Z = Amount of lowest layer

NOTE: This element is only recorded for data prior to June 1,1951. Check
Flags 1 and 2 for further definition of CC51. C-A-U-T-I-O-N must be
taken when using this element.

Sky condition is a descriptive symbolic coding of the state of the sky,
referring in general to the amount of the celestial dome covered by
clouds or obscuring phenomena.

[X and Z Code Amounts]{.underline}

0 = clear or less than .1 coverage

1 = thin scattered

2 = scattered

3 = dark scattered

4 = thin broken

5 = broken

6 = dark broken

7 = thin overcast

8 = overcast

9 = dark overcast

\- = obscuration 10/10ths obscuration

b = (blank) partial obscuration

[YY Code]{.underline}

> 00 - 95 = Height in hundreds of feet
>
> 96 = Value unknown. Manuscript entry was \>bb\'(blanks).
>
> 97 = No low scattered clouds. Manuscript entry was \'\_\_\_\'(line).
>
> 98 = Invalid original value. Manuscript entry was \'\*\*\'.
>
> 99 = 10,000 feet or higher.

###### CLC\"x\"

DESCRIPTION: Sky condition in tenths and cloud coverage by layer.

VALID TIMES: through current

STATION TYPES: Human observer stations only

COMMENTS: Beginning July 1, 1996 with the implementation of the METAR
code, the element CLC@x@ (tenths) was derived from CLM@x@ (eights) and a
maximum of 6 cloud layers may be reported. Prior to July 1, 1996, the
element CLC@x@ was directly observed in tenths and an infinite number@
of cloud layers could be reported.

The sky condition. The \"x\" indicates the layer where:

1 = Lowest cloud layer

2 = 2nd cloud layer

3 = 3rd cloud layer

4 = 4th cloud layer

5 = 5th cloud layer

6 = 6th cloud layer

N = N\'th cloud layer if necessary

(prior to July 1, 1996 only)

Cloud information pertaining to sky condition and cloud coverage is
contained within one element per level. Check data Flags 1 and 2 for
further definition.

The DATA-VALUE portion of the record will appear as: Example 0XXYY
constitutes the five character field where:

XX = code for sky condition

YY = cloud coverage (tenths)

[XX Code - Sky Condition]{.underline}

00 = Clear or less than .1 coverage

01 = thin scattered .1 to .5 coverage (used before July 1996)

02 = scattered .1 to .5 coverage

03 = thin broken .6 to .9 coverage (used before July 1996)

04 = broken .6 to .9 coverage

05 = thin overcast 1.0 coverage (used before July 1996)

06 = overcast 1.0 coverage

07 = obscuration 1.0 coverage

08 = partial obscuration \<1.0 coverage (used before July 1996)

09 = unknown

[YY Code - Cloud Coverage]{.underline}

> Cloud coverage is expressed in tenths.

00 = Clear conditions (with \>00\' code for XX)

99 = Unknown value (with \>09\' code for XX)

NOTE: Prior to 1984, if the sky was totally clear of clouds then
CLC\"x\" is not reported and the TSKC (Total Sky Cover) element appears
as \"00000\". It indicates that some cloud type less than .1 coverage
was observed and not a clear sky condition.

###### CLM\"x\"

DESCRIPTION: Sky condition in eights and cloud coverage by layer.

VALID TIMES: July 1, 1996 through current

STATION TYPES: Human observer stations only

COMMENTS: Beginning July 1, 1996 with the implementation of the METAR
code, the element CLC@x@ (tenths) was derived from CLM@x@ (eights)and a
maximum of 6 cloud layers may be reported.

Sky condition and height contained within one element per layer. The
\"x\" indicates the layer where:

1 = The lowest layer

2 = The second layer

3 = The third layer

4 = The fourth layer

5 = The fifth layer

6 = The sixth layer

The DATA-VALUE portion of the record will appear as 0XXYY where:

XX = The code for sky condition.

YY = The cloud coverage expressed in eighths.

[XX Code - Sky Condition]{.underline}

00 = Clear

01 = few scattered 1/8 to 2/8 coverage

02 = scattered 3/8 to 4/8 coverage

04 = broken 5/8 to 7/8 coverage

06 = overcast 8/8 coverage

07 = obscuration 8/8 coverage

09 = unknown

Note: This XX code is the same used for the element ALM\"x\", the ASOS
station version of CLM@x@.

[YY Code - Cloud Coverage]{.underline}

Cloud coverage is expressed in eighths.

00 = Clear conditions (with \>00\' code for XX)

99 = Unknown value (with \>09\' code for XX)

###### CLHT

DESCRIPTION: Ceiling height

VALID TIMES: through current

STATION TYPES: ASOS, ASOS augmented and Human observer stations

COMMENTS: Since July 1, 1996, the METAR code does not distinguish
between thin and opaque clouds. In addition, beginning 9/1992, the
implementation of ASOS celiometers does not distinguish between thin and
opaque clouds. These two changes result in all clouds being considered
opaque after either of these two changes became effective. Prior to
these two changes, thin clouds were not included in ceiling height.

Ceiling height is defined as the height of the lowest sky cover layer
that is more than 1/2 opaque. Heights are defined in hundreds of feet.
The DATA-VALUE will appear as 00XXX. Range of values = 00000 to 99999. A
value of 99999 indicates an unlimited ceiling. The unknown or missing
value is 00999.

The NWS Automated Surface Observing System (ASOS) began implementation
at stations in September 1992. Sky and ceiling information are
automatically derived from ceilometer data in the ASOS. The ASOS cloud
height is an estimate based on the heights of clouds detected every 30
seconds during the previous 30 minutes (with the last 10 minutes of data
double weighted). The ASOS ceilometer measures clouds at or below 12,000
feet. ASOS Augmented sites and human observer sites can also report
ceiling heights greater than 12,000 feet.

###### CLT\"x\"

DESCRIPTION: The cloud type and height by layer.

VALID TIMES: through current

STATION TYPES: ASOS Augmented and Human observer stations only

COMMENTS: Since July 1, 1996, the METAR code only allows the reporting
of CB (Cumulonimbus) and TC (Towering Cumulus) cloud types. However,
human observer stations using the MAPSO system can report other cloud
types and obscuring phenomena listed below.

The \"x@ indicates the layer where:

1 = lowest cloud layer or obscuring phenomena

2 = 2nd cloud layer

3 = 3rd cloud layer

4 = 4th cloud layer

5 = 5th cloud layer

6 = 6th cloud layer

N = Nth cloud layer if necessary (before July 1996 only)

Cloud information pertaining to cloud type and cloud height is contained
within one element per level. The DATA-VALUE portion of the record will
appear as: XXYYY.

XXYYY constitutes the five character field where:

> XX = Code for cloud type (or obstruction to vision code at lowest
> cloud layer) code listed below.
>
> YYY = Cloud height (hundreds of feet)

9\'s for any unknown value.

NOTE: (1) Cloud type/obscuring phenomena code check Flags 1 and 2 for
further definition.

\(2\) Prior to 1984, if any of the four layers (maximum number of layers
reported) were obscured the remaining layers appear as \"00999\"
indicating \"no clouds\". If the sky was totally clear of clouds then
CLT\'x\" was not reported. After 1984 only those cloud layers observed
are indicated.

Generic cloud type or obscuring phenomena codes are:

[CLOUD TYPE]{.underline} [ABBREVIATION]{.underline}

00 = None

11 = Cumulus CU

12 = Towering Cumulus TCU

13 = Stratus Fractus STFRA

14 = Stratus Cumulus Lenticular SCSL

15 = Stratus Cumulus SC

16 = Stratus ST

17 -- Cumulus Fractus CUFRA

18 = Cumulonimbus CB

19 = Cumulonimbus Mammatus CBMAM

21 = Altostratus AS

22 = Nimbostratus NS

23 = Altocumulus AC

24 = Altocumulus Lenticular ACSL

28 = Altocumulus Castellanus ACCAS

29 = Altocumulus Mammatus ACMAM

32 = Cirrus CI

35 = Cirrocumulus Lenticular CCSL

37 = Cirrostratus CS

39 = Cirrocumulus CC

OBSCURING PHENOMENA ([Began Jan. 1984)]{.underline}

01 = Blowing spray BY

03 = Smoke and haze KH or HK

04 = Smoke K

05 = Haze H

06 = Dust D

07 = Blowing dust BD

08 = Volcanic ash (begin Aug. 92) VA

30 = Blowing sand N or BN

36 = Blowing snow BS

44 = Ground fog GF

45 = Fog F

48 = Ice fog IF

50 = Drizzle L or ZL

60 = Rain R or RW or ZR

70 = Snow S or SP or SW or SG

76 = Ice crystals IC

98 = Obscuring phenomena other than fog (prior to 1984)

###### C2C3

DESCRIPTION: The total amount of sky cover by the first two cloud layers
and the first three cloud layers.

VALID TIMES: through current

STATION TYPES: Human Observer sites only

COMMENTS: Since July 1, 1996, the METAR code requires the reporting of
sky cover in eighths. Prior to July 1, 1996, sky cover is in tenths.
This element is not used for ASOS or ASOS augmented observations.

DATA-VALUE will appear as 0XXYY where:

Prior to JULY 1996:

XX = Summation of first two cloud layers (10ths)

YY = Summation of first three cloud layers (10ths)

Range = 00 through 10 and 99.

00 = Clear or \< .1

01 = 0.1

02 = 0.2

03 = 0.3

04 = 0.4

05 = 0.5

06 = 0.6

07 = 0.7

08 = 0.8

09 = 0.9

10 = 1.0

99 = Unknown or missing

Beginning JULY 1996:

XX = Summation of first two cloud layers (8ths)

YY = Summation of first three cloud layers (8ths)

Range = 00 through 08 and 99.

00 = Clear or \< 1/8

01 = 1/8

02 = 2/8

03 = 3/8

04 = 4/8

05 = 5/8

06 = 6/8

07 = 7/8

08 = 8/8

99 = Unknown or missing

###### DPTC

DESCRIPTION: Dew Point Temperature in tenths degree Celsius.

VALID TIMES: Beginning July 1, 1996 through current

STATION TYPES: All stations, ASOS, ASOS, Augmented and Human Observer
stations

COMMENTS: Since July 1, 1996, the element DPTP (degrees Fahrenheit) was
derived from the element DPTC (tenth=s degree Celsius).

The DATA-VALUE will appear as 00XXX.

Range of values: 00000 to 00600 (positive and negative)

Unknown or Missing: 00999

Measured to tenths degrees Celsius

###### DPTP

DESCRIPTION: Dew Point Temperature in degrees Fahrenheit.

VALID TIMES: Through current

STATION TYPES: All stations (ASOS, ASOS Augmented and Human Observer
stations)

COMMENTS: Since July 1, 1996, the element DPTP (degrees Fahrenheit) was
derived from the element DPTC (tenth=s degree Celsius).

The DATA-VALUE will appear as 00XXX.

Range of values: 00000 to 00140 (positive and negative)

Measured or derived to whole degrees F.

###### HZVS

DESCRIPTION: The prevailing Horizontal Visibility

VALID TIMES: Through current

STATION TYPES: All stations, ASOS, ASOS Augmented, and Human Observer
stations

The DATA-VALUE will appear as XXXXX. Range of value = 00000 to 99999. A
value of 99999 indicates unknown or unlimited visibility (\> 100 miles).
Horizontal visibility is usually reported at an elevation of 6 feet
above the ground.

The following code is used:

[HZVS CODE]{.underline}

Reported by Archive Actual visibility

ASOS Manned Code (in miles)

Yes 00000 Zero visibility

> Yes 00006 1/16 miles
>
> Yes 00012 1/8 miles

Yes Yes 00019 3/16 (ASOS \<1/4 miles)

Yes Yes 00025 1/4 miles

Yes 00031 5/16 miles

> Yes 00038 3/8 miles

Yes Yes 00050 1/2 miles

> Yes 00062 5/8 miles

Yes Yes 00075 3/4 miles

Yes 00081 3/4 or 7/8-see note below

> Yes 00087 7/8 miles

Yes Yes 00100 1 mile

Yes 00112 1 1/8 miles

Yes Yes 00125 1 1/4 miles

Yes 00138 1 3/8 miles

Yes Yes 00150 1 1/2 miles Yes 00162 1 5/8 miles

Yes Yes 00175 1 3/4 miles

Yes Yes 00200 2 miles

Yes 00225 2 1/4 miles

Yes Yes 00250 2 1/2 miles

Yes 00275 2 3/4 miles

Yes Yes 00300 3 miles

Yes 00350 3 1/2 mi.(ASOS only)

Yes Yes 00400 4 miles

Yes Yes 00500 5 miles

Yes Yes 00600 6 miles

Yes Yes 00700 7 miles

Yes Yes 00800 8 miles

Yes Yes 00900 9 miles

Yes Yes 01000 10 miles(ASOS 10+ miles)

Yes 10000 100 Miles

Yes 99999 Unknown or Unlimited(See Flag 1)

NOTE 1. Historical data archived prior to Jan. 1984 did not
differentiate between 3/4 and 7/8 visibilities. This historical data was
converted from TD1440 to TD3280 coded as \>00081\'. 2) In September 1992
Automated Surface Observing Systems began to be commissioned at NWS, FAA
and DOD sites. The automated visibility sensors report values in the
range of \< 1/4 to 10+ miles. These reportable ASOS values are indicated
in the table above along with those values reportable by human
observers.

NOTE 2. For data converted from Datsav3 Surface input, values other than
those appearing in the above table may appear in the data. These values
represent miles and hundredths; example \-- 126 = 1.26 miles visibility.
Simply divide by 100 to get the decimal value in miles.\"

###### PRES

DESCRIPTION: The station pressure

VALID TIMES: Through current

STATION TYPES: All stations (ASOS, ASOS Augmented and Human Observer
stations)

The station pressure at station level in inches and thousandths of
mercury. The DATA-VALUE will appear as XXXXX.

Range of values: 19000 to 39990

*NOTE: For ASOS stations, station pressure is not reported after June
1996 with the implementation of the METAR code. See element ALTP
(Altimeter setting)*

**[PWTH]{.underline}**

DESCRIPTION: The present (or prevailing) weather occurring at the time
of the observation.

VALID TIMES: Through current

STATION TYPES: All stations (ASOS, ASOS Augmented and Human Observer
stations)

Present weather codes are two characters in length. The leftmost
character indicates the general class of present weather while the
rightmost character is a qualifier.

The two digit codes are stored into the five digits of the DATA-VALUE
portion. \*\*\*If there is no occurrence of present weather the valid
DATA-Value will always be 00000. Within the five digits used, the
leftmost digit is always set to zero. Through June 1996, the two-digit
weather codes are entered left justified for the remaining four digits.
From July 1996 through present, the two-digit weather codes are right
justified. For example, moderate snow would be coded as 04100 through
June 1996. From July 1996 through present, moderate snow is coded as
00041. If two types of weather occur for the same hour, the value field
would appear as 0XXYY. For example, light rain and fog occurring on the
same hour would be coded as 02070.

Until July 1996, if more than two types occur for the same hour, they
will be stored into additional PWTH records as necessary. Beginning July
1996, if more than two types occur for the same hour they will be stored
in additional Data Groups within the same record.

Consider the following examples:

On day 11 Feb 1981 at 1200 (noon) and 1300 hours no present weather
occurred.

0054HLY00005264PWTHNA19810211110021200b00000b11300b00000b1

On day 11 Feb 1981 at 1200 (noon) light snow, light freezing rain, ice
fog, and blowing snow all occur. The records will appear as:

0042HLY000005264PWTHNA1981021111001120004026b1

0042HLY000052664PWTHNA1981021111001120007184b1

On day 4 Apr, 2001 at 1400 thunderstorm, light rain and fog/mist all
occur. The record will appear as follows:

HLY00003017PWTHNA200104A1060251400 01020 01400 00070 0

PRESENT WEATHER CODES descriptions follow:

[CODE FOR PWTH RANGE 00.]{.underline}

00 \*\*\*\*\*\*\*\*\*\* No Occurrence where:

00 = No present weather occurred

[CODE FOR PWTH RANGE 10 TO 19.]{.underline}

1X \*\*\*\*\*\*\*\*\*\* Thunderstorm, Tornado, Squall where:

> X = 0 thunderstorm - lightning and thunder. Wind gust \< 50 knots -
> hail \< .75 inches. Beginning July 1996 a thunderstorm is defined as a
> local storm produced by a cumulonimbus cloud that is accompanied by
> lighting and/or thunder. Intensity attributed to frequency of
> lighting, speed of wind gust, and size of hail ended June 1996.
>
> = 1 heavy or severe thunderstorm frequent intense lightning and
> thunder. Wind gust 50 knots or greater - hail .75 inches or greater
> (ends June 1996).
>
> = 2 report of tornado or water spout
>
> = 3 light squall (through May 1951 only)
>
> = 4 moderate squall - Beginning in June 1951, only this code (14) is
> recorded.

Code 13 and 15 are recorded beginning in January 1949 and ending in May
1951. Prior to 1949 rain squalls are distinguished from snow squalls and
recorded in separate general classes of present weather. A squall is a
sudden increase of wind speed by at least 16 knots, reaching 22 knots or
more and lasting for at least one minute.

> = 5 heavy squall (through May 1951 only)

= 6 water spout (began Jan 1984 and ends June 1996)

= 7 funnel cloud (began Jan 1984)

> = 8 tornado (began Jan 1984 and ends June 1996)
>
> = 9 unknown

[CODE FOR PWTH RANGE 20 TO 29]{.underline}

> 2X \*\*\*\*\*\*\*\*\* Rain, Rain Showers, Freezing Rain where:
>
> X = 0 light rain
>
> = 1 moderate rain

= 2 heavy rain

= 3 light rain showers

= 4 moderate rain showers

= 5 heavy rain showers

= 6 light freezing rain

= 7 moderate freezing rain

= 8 heavy freezing rain

= 9 unknown

[CODE FOR PWTH RANGE 30 TO 39]{.underline}

3X \*\*\*\*\*\*\*\*\* Rain Squalls, Drizzle, Freezing Drizzle where:

X = 0 light rain squalls (through 1948 only)

= 1 moderate rain squalls (through 1948 only)

= 2 heavy rain squalls (through 1948 only)

= 3 light drizzle

= 4 moderate drizzle

= 5 heavy drizzle

= 6 light freezing drizzle

= 7 moderate freezing drizzle

= 8 heavy freezing drizzle

= 9 unknown. Beginning Sept 1992 the Automated Surface Observing System
(ASOS) can report unknown precipitation. This is an indication of light
precipitation and is reported when the precipitation discriminator
detects, but cannot recognize the type of precipitation.

[CODE FOR PWTH RANGE 40 TO 49]{.underline}

4X \*\*\*\*\*\*\*\*\* Snow, Snow Pellets, Ice Crystals where:

X = 0 light snow

= 1 moderate snow

= 2 heavy snow

= 3 light snow pellets (ends June 1996)

= 4 moderate snow pellets (ends June 1996

= 5 heavy snow pellets (ends June 1996)

= 6 light ice crystals (ends March 1963)

= 7 moderate ice crystals

= 8 heavy ice crystals (ends March 1963)

= 9 unknown

Beginning April 1963 any occurrence of ice crystals is recorded as a 47.
Prior to this date intensities were reported. Code 43, 44, 45 ended June
1996 and were reported in code 67.

[CODE FOR PWTH 50 TO 59]{.underline}

5X \*\*\*\*\*\*\*\*\* Snow Showers, Snow Squalls, Snow Grains

where:

X = 0 light snow showers

= 1 moderate snow showers

= 2 heavy snow showers

= 3 light snow squall (through 1948 only)

= 4 moderate snow squall (through 1948 only)

= 5 heavy snow squall (through 1948 only)

= 6 light snow grains

= 7 moderate snow grains

= 8 heavy snow grains

= 9 unknown

[CODE FOR PWTH RANGE 60 TO 69]{.underline}

> 6X \*\*\*\*\*\*\*\*\* Sleet, Sleet Showers, Hail

where:

X = 0 light ice pellet showers

= 1 moderate ice pellet showers

= 2 heavy ice pellet showers

= 3 light hail (see note below)

= 4 moderate hail (see note below)

= 5 heavy hail (see note below)

= 6 light small hail (see note below)

= 7 moderate small hail (see note below)

= 8 heavy small hail (see note below)

= 9 unknown

Prior to April 1970 ice pellets were coded as sleet. Beginning April
1970 sleet and small hail were redefined as ice pellets and are coded as
60, 61 or 62. Beginning September 1956 intensities of hail were no
longer reported and all occurrences were recorded as a 64. Beginning
July 1996 hail was defined as hailstones 1/4 inch or larger in diameter;
small hail and snow pellets are reported when less than 1/4 inch in
diameter and are coded as 64 and 67, respectively.

[CODE FOR PWTH RANGE 70 TO 79]{.underline}

> 7X \*\*\*\*\*\*\*\*\* Fog, Blowing dust, Blowing Sand where:
>
> X = 0 fog/mist. Beginning July 1996 fog was redefined as a visible
> aggregate of minute water particles (droplets) which are based at the
> earth\'s surface and reduces the horizontal visibility to less than
> 5/8 statute miles. Mist is defined as a visible aggregate of minute
> water particles suspended in the atmosphere that reduces visibility to
> less than 7 statute miles but greater than or equal to 5/8 statute
> miles.

= 1 ice fog / freezing fog

= 2 ground fog

= 3 blowing dust

= 4 blowing sand

= 5 heavy fog

= 6 glaze (begin 1984)

= 7 heavy ice fog (begin 1984)

= 8 heavy ground fog (begin 1984)

= 9 unknown

All of the above values are recorded only when visibility is less than 7
miles. Beginning July 1996 ice fog is called freezing fog and is coded
as 71.

[CODE FOR PWTH RANGE 80 TO 89]{.underline}

> 8X \*\*\*\*\*\*\*\* Smoke, Haze, Smoke and Haze, Blowing Snow, Blowing
> Spray, Dust where:

X = 0 smoke

= 1 haze

= 2 smoke and haze

= 3 dust

= 4 blowing snow

= 5 blowing spray

= 6 dust storm (begin 1984)

= 7 volcanic ash (begin Aug.1992)

= 8 not used

= 9 unknown

These values are recorded only when visibility is less than 7 miles.

[CODE FOR PWTH RANGE 90 TO 97 AND 99]{.underline}

> CODE FOR PWTH RANGE 90 TO 97
>
> 9X \*\*\*\*\*\* Ice Pellets, Hail Showers, Small Hail/Snow Pellet
> Showers, Fog (partial, patches), snow (low drifting) where:

X = 0 light ice pellets

= 1 moderate ice pellets

= 2 heavy ice pellets

= 3 hail showers (begins July 1996)

= 4 small hail/snow pellet showers(begins July 1996)

= 5 partial fog (begins July 1996)

= 6 patches fog (begins July 1996)

= 7 low drifting snow (begins July 1996)

= 9 unknown

###### PWVC

DESCRIPTION: The present (or prevailing) weather occurring between 5 and
10 statute miles at the time of the observation in the vicinity of the
observation.

VALID TIMES: From July 1, 1996 through current.

STATION TYPES: All stations (ASOS, ASOS Augmented and Human Observer
stations)

COMMENTS: The element PWVC began with the implementation of the METAR
code on July 1, 1996.

PWVC weather codes are two characters in length. The two digit codes are
stored into the five digits of the DATA-VALUE portion. \*\*\*If there is
no occurrence of PWVC, the DATA-Value is not archived.

Within the five digits used, the leftmost digit is always set to zero.
The two-digit weather codes are always right justified. For example,
showers in the vicinity would be coded as 00002. If two types of weather
in the vicinity occur for the same hour, the value field would appear as
0XXYY. For example, a thunderstorm in the vicinity and shower in the
vicinity would be coded as 00102.

If more than two types of weather in the vicinity occur for the same
hour, they will be stored into additional PWVC records as necessary. See
element PWTH for examples.

PWVC DATA-VALUE code descriptions follow:

Code Description

00 no occurrence

01 Thunderstorm in vicinity

02 Showers in vicinity

03 Sandstorm in vicinity

04 Sand / Dust whirls in vicinity

05 Duststorm in vicinity

06 Blowing snow in vicinity

07 Blowing sand in vicinity

08 Blowing dust in vicinity

09 Fog in vicinity

###### RHUM

DESCRIPTION: Relative Humidity

VALID TIMES: Through current.

STATION TYPES: All stations (ASOS, ASOS Augmented and Human Observer
stations)

Relative Humidity expressed in whole percent. The DATA-VALUE will appear
as 00XXX.

Range of values: 00000 to 00100

###### SLVP

DESCRIPTION: Sea level pressure

VALID TIMES: Through current.

STATION TYPES: All stations (ASOS, ASOS Augmented and Human Observer
stations)

Pressure, reduced to sea level, expressed in millibars and tenths. The
DATA-VALUE will appear as XXXXX.

Range of values: 09200 to 10900

###### TMCD

DESCRIPTION: Dry Bulb Air Temperature in tenths degree Celsius.

VALID TIMES: Beginning July 1, 1996 through current

STATION TYPES: All stations (ASOS, ASOS Augmented and Human Observer
stations)

COMMENTS: Since July 1, 1996, the element TMPD (whole degrees
Fahrenheit) was derived from the element TMCD (tenths of degree
Celsius).

The DATA-VALUE will appear as 00XXX.

Range of values: 00000 to 00600 (positive or negative)

Measured to tenths degree Celsius

###### TMPD

DESCRIPTION: Dry Bulb Air Temperature in whole degrees Fahrenheit.

VALID TIMES: Through current

STATION TYPES: All stations (ASOS, ASOS Augmented and Human Observer
stations)

COMMENTS: Since July 1, 1996, the element TMPD (whole degrees
Fahrenheit) was derived from the element TMCD (tenths of degree
Celsius).

The DATA-VALUE will appear as 00XXX.

Range of values: 00000 to 00140 (positive or negative)

Measured or derived to whole degrees F.

###### TMPW

DESCRIPTION: Wet bulb Temperature in degrees Fahrenheit to tenths.

VALID TIMES: Through current

STATION TYPES: All stations (ASOS, ASOS Augmented and Human Observer
stations)

COMMENTS: The element TMPW is derived from the dry bulb and dew point
temperature. Prior to July 1, 1996, dry bulb and dew point temperatures
were observed in degrees Fahrenheit. Since July 1, 1996, dry bulb and
dew point temperatures are observed in tenths of degree Celsius with the
implementation of the METAR code.

The DATA-VALUE will appear as 0XXXX.

Range of values: 00000 to 01400 (positive or negative)

###### TSCE

DESCRIPTION: Total sky cover, measured in eighths.

VALID TIMES: July 1, 1996 through current

STATION TYPES: Human observer sites only

COMMENTS: The METAR code does not distinguish between thin and opaque
clouds.

TSCE describes the amount of the celestial dome covered by clouds or
obscuring phenomena.

The DATA-VALUE will appear as 0XXYY where XX is the total sky cover. YY
which is the total opaque sky cover, is not reportable by the METAR code
and is always assigned as missing and coded 99.

00 = clear

01 = scattered clouds 1/8 coverage

02 = scattered clouds 2/8 coverage

03 = scattered clouds 3/8 coverage

04 = scattered clouds 4/8 coverage

05 = broken clouds 5/8 coverage

06 = broken clouds 6/8 coverage

07 = broken clouds 7/8 coverage

08 = overcast 8/8 coverage

99 = missing or unknown

###### TSKC

DESCRIPTION: Total sky cover and total opaque sky cover measured in
tenths

VALID TIMES: Through current

STATION TYPES: Human observer sites only

COMMENTS: Since July 1, 1996, 1) the METAR code does not distinguish
between thin and opaque clouds and 2) the element TSKC (tenths) was
derived from the element TSCE (eights).

The amount of the celestial dome covered by clouds or obscuring
phenomena. Opaque means clouds or obscuration through which the sky or
higher cloud layers cannot be seen. Range of value 00 to 10 (tenths) and
99.

The DATA-VALUE will appear as 0XXYY where XX is the total sky cover. YY
is the total opaque sky cover. Since July 1, 1996, opaque sky cover is
not reportable by the METAR code and is always assigned as missing and
coded 99.

00 = clear or less than .1 coverage

01 = scattered clouds .1 coverage

02 = scattered clouds .2 coverage

03 = scattered clouds .3 coverage

04 = scattered clouds .4 coverage

05 = scattered clouds .5 coverage

06 = broken clouds .6 coverage

07 = broken clouds .7 coverage

08 = broken clouds .8 coverage

09 = broken clouds .9 coverage

10 = overcast 1.0 coverage

99 = missing or unknown

###### WD16

DESCRIPTION: Wind direction and speed to 16 point WBAN code

VALID TIMES: Through December 31, 1963

STATION TYPES: Human observer sites only

COMMENTS: Old code not used since December 31, 1963. Beginning 1 Jan
1964 wind directions were observed and coded to tens of degrees (see
elements WIND and WND2).

Direction is the direction from which the wind is blowing. Speed in
knots.

WIND DIRECTION CODES

(through Dec. 1963 only)

16 Pt

WBAN Code Degrees

00 = Calm Calm

11 = N 349-011

12 = NNE 012-033

22 = NE 034-056

32 = ENE 057-078

33 = E 079-101

34 = ESE 102-123

44 = SE 124-146

54 = SSE 147-168

55 = S 169-191

56 = SSW 192-213

66 = SW 214-236

76 = WSW 237-258

77 = W 259-281

78 = WNW 282-303

88 = NW 304-326

18 = NNW 327-348

99 = Unknown

Example of DATA-VALUE XXYYY for wind direction (XX) and speed (YYY):
12037 wind is from the NNE at 37 knots. 12 = wind from NNE. 037 = wind
speed is 37 knots.

###### WIND

DESCRIPTION: Wind Direction and Speed

VALID TIMES: January 1, 1964 through current

STATION TYPES: Human observer sites only

COMMENTS: WIND (10\'s of Degrees Code) element begins January 1964.
Prior to 1964 winds observed in the WD16 (16 point code). In September
1992 with the implementation of ASOS, the element WND2 is used when a
station converted to ASOS. With the implementation of the METAR code on
July 1, 1996, the definitions for calm and variable wind changed as
described below.

Direction is the direction from which the wind is blowing. Speed is in
knots. Range of values (direction) = 00 to 36 and 99. Range of value
(speed) = 000 to 250.

Example of DATA-VALUE XXYYY for wind direction (XX) and speed (YYY):
02037 wind is from 020 degrees at 37 knots. 02 = wind 020 degrees. 037 =
wind speed is 37 knots.

WIND DIRECTION CODES (begin 1964)

10\'s of

Degrees Code Degrees

00 = Calm (see note below)

01 = 010

02 = 020

. = .

. through .

. .

36 = 360

99 = Unknown

Since July 1, 1996 calm and variable winds are defined as follows:

\- Calm winds include wind speeds of 0 to 2 knots and are coded as 00000

\- Variable winds include wind speeds of 3-6 knots and are coded as
99003 through 99006

Example 99004 is a variable wind at 4 knots.

###### WND2

DESCRIPTION: Wind Direction and Speed from ASOS

VALID TIMES: September 1992 through current

STATION TYPES: ASOS and ASOS Augmented sites only

COMMENTS: In September 1992 with the implementation of ASOS, the element
WND2 is used when a station converted to ASOS. With the implementation
of the METAR code on July 1, 1996, the definitions for calm and variable
wind changed as described below.

ASOS wind speeds are two-minute averages in knots. Direction is the
direction (in tens of degrees) from which the wind is blowing.

The DATA VALUE portion of the record will appear as XXYYY where:

> XX = The direction in tens of degrees. 00 = calm, 36 = 360 degrees.

YYY = The speed of the wind in knots.

Example: 28014 is a wind from 280 degrees at 14 knots. 28 = wind 280
degrees. 014 = wind speed is 14 knots.

Since July 1, 1996 calm and variable winds are defined as follows:

> \- Calm winds include wind speeds of 0 to 2 knots and are coded as
> 00000
>
> \- Variable winds include wind speeds of 3-6 knots and are coded as
> 99003 through 99006

Example 99004 is a variable wind at 4 knots.

**ELEMENT - UNITS**

> The unit and decimal position of the DATA-VALUE of this record.

ELEMENT-UNITS TABLE

DT Wind direction in tens of degrees

F Whole degrees Fahrenheit

HF Hundreds of feet

HM Miles and hundredths

IH Inches and hundredths of mercury

IT Inches and thousandths of mercury

KD knots and direction in tens of degrees

KS Knots and direction in 16 point WBAN Code

MT Millibars and tenths

NA No units applicable (non-dimensional)

N1 No units applicable - element to tenths

N2 No units applicable - element to hundredths

P Whole percent

TC Degrees Celsius in tenths

TF Degrees Fahrenheit in tenths

WH Watt hour per meter squared

NOTE: All entries are left justified and blank filled.

### YEAR

This is the year of the record. Range of value is 1900 to the current
year processed.

#### MONTH

This is the month of record. Range of value is 01-12.

###### SOURCE CODE-1

Contains a code indicating the primary source of the original record
this element was taken from. Range is 1-9.

SOURCE CODE TABLE

1 Original Manuscript

2 SRRS

3 AFOS

4 DATSAV

5 NMC

6 Foreign Keyed

7 MAPSO

8 SRRS plus

9 Other/unknown

A ASOS

Source codes reflect normally expected data sources and do not
necessarily indicate the actual source of a specific item. Pre-1984 data
will be coded as a 1.

###### SOURCE CODE-2

Contains a code indicating the back-up source of the original record
this element was taken from. Range is 1-9.

SOURCE CODE TABLE

1 Original Manuscript

2 SRRS

3 AFOS

4 DATSAV

5 NMC

6 Foreign Keyed

7 MAPSO

8 SRRS plus

9 Other/unknown

A ASOS

Pre-1984 data will be coded as a 1.

###### DAY

Contains the day of the record. Range 01-31.

##### NUM-VALUES

This notates the actual number of values reported. Range of values is
001-048.

*NOTE: A record may contain fewer or more data values than you might
expect. A daily record or hourly value may contain as few as one data
value or as many as 48. This is primarily due to missing or edited data.
If a particular data value was not taken or is unavailable there is no
entry for it. Also, when erroneous data are encountered during quality
control the original value is flagged and could be followed by a
replacement value (see FLAG-2 TABLE for details).*

###### TIME-OF VALUE

Contains the hour and minute of the hourly element value. Range is
0000-2300. The hour is in the leftmost two digits and the minute is in
the rightmost two digits. Minutes are always 00. Hour is reported using
the 24 hour clock. The time entered is that of the record observation,
taken within 10 minutes prior to the hour (e.g., 1353 punched 14 and now
archived as 1400). Prior to June 1957, observations were taken within 10
minutes prior to the half hour with minutes disregarded in keying (e.g.,
1224 punched 12 and now archived as 1200). Observation times were keyed
in Local Standard Time.

###### SIGN OF METEOROLOGICAL VALUE

This is the \'SIGN\' of the meteorological data value (Tape Field 013).
This field contains either 1) a blank indicating a positive value or 2)
a minus sign indicating a negative value. A plus is not used to indicate
a positive value.

###### DATA-VALUE

Actual data value. This field is a five-digit integer. Unit and decimal
position of the data value are indicated in the ELEMENT-UNITS field
described in Tape Field 004.

###### FLAG-1

The data measurement FLAG.

FLAG-1 TABLE (Measurement Value)

> (Valid for all elements except GRAD and DRAD.)
>
> C Ceiling of cirroform clouds at unknown height (Sep 56 - Mar 70)

D Derived value

E Estimated value

G Visibility \> or = 100 miles (data value = 10000)

M Visibility missing (data value = 99999)

N Unlimited visibility (data value = 99999)

> R Dew Point and/or Relative Humidity, originally calculated with
> respect to ice have been recomputed with respect to water. (DPTP,RHUM)
>
> U Unlimited ceiling height (DATA-VALUE = 99999). (CLHT)

b (blank) Flag not needed. (All elements except CC51)

The following 4 flags apply only to the \'CC51\' element type produced
for cloud coverage prior to July 1951.

> B The 0 found in byte 2 of CC51 should be a \'b\' = thin obscuration.
>
> \* The 0 found in byte 2 of CC51 should be a \'\*\' = original value
> invalid.
>
> \- The 0 found in byte 2 of CC51 should be a \'-\' = total
> obscuration.
>
> 9 The digit found in byte 2 of CC51 (high cloud amount) is a valid
> code. See Pre-June 1951 Cloud Cover Table.

The following flags apply only to the \'DRAD\' and \>GRAD= elements.
These flags appear as a pair in flag positions one and two. At NOAA's
Atmospheric Research Laboratory in Oak Ridge, Tennessee, the data
processes through a quality control procedure and daily plotting of time
series. The passed 15-minute mean values are also tested against the
Solar Energy Research Institute (SERI, but now National Renewable Energy
Laboratory) Quality Control (SERI QC) software. The SERI QC generates
flags for global, normal incident, and diffuse global radiation. This
quality control primarily flags data that departs from expected limits
and boundaries. Flagging convention follows:

> 00 Untested (raw data)
>
> 01 Passed one-component test; data fall within max-min limits of Kt,
> Kn, or Kd
>
> 02 Passed two-component test; data fall within 0.03 of the Gompertz
> boundaries
>
> 03 Passed three-component test; data come within [+]{.underline} 0.03
> of satisfying Kt = Kn + Kd
>
> 04 Passed visual inspection: not used by SERI_QC1
>
> 05 Failed visual inspection: not used by SERI_QC1
>
> 06 Value estimated; passes all pertinent SERI_QC tests
>
> 07 Failed one-component test; lower than allowed minimum
>
> 08 Failed one-component test; higher than allowed maximum
>
> 09 Passed three-component test but failed two-component test by 0.05
>
> 10-93 Failed two- or three- component tests in one of four ways. To
> determine the test failed and the manner of failure (high or low),
> examine the remainder of the calculation (flag+2)/4.
>
> [Rem]{.underline} [Failure]{.underline}
>
> 0 Parameter too low by three-component test (Kt = Kn + Kd)
>
> 1 Parameter too high by three component test (Kt = Kn + Kd)
>
> 2 Parameter too low by two-component test (Gompertz boundary)
>
> 3 Parameter too high by two-component test (Gompertz boundary)

The magnitude of the test failure (distance in K-units) us determined
from: d = (INT(flag + 2)/4)100.

> 94-97 Data fails into physically impossible region where Kn \> Kt by
> K-space distances of 0.05 to 0.10 (94), 0.10 to 0.15 (95), 0.15 to
> 0.20 (96), and [\>]{.underline} 0.20 (97).
>
> 98 Not used
>
> 99 Missing data

###### FLAG-2

The data quality FLAG.

FLAG-2 (Quality Flag)

> (Valid for all elements except CC51, GRAD and DRAD. For GRAD and DRAD,
> see information under **[FLAG-1]{.underline}** above.)
>
> 0 Observed data has passed all internal consistency checks.
>
> 1 Validity indeterminable (primarily for pre-1984 data).
>
> 2 Observed data has failed an internal consistency check - subsequent
> edited value follows observed value.
>
> 3 Data beginning January 1,1984 - observed data has failed a
> consistency check - No edited value follows.
>
> Data prior to 1 Jan 84 - observed data exceeded preselected
> climatological limits during conversion from historic TD-1440 files.
> No edited value follows.
>
> 4 Observed data value invalid - no edited value follows.
>
> 5 Data converted from historic TD-1440 exceeded known climatological
> extremes - no edited value follows.
>
> E Edited data value passes all system checks - no observed value
> present.
>
> M Manually edited data value added to data set after original
> archival. Automated edit not performed on this item.
>
> S Manually edited data passes all system checks.

The following 4 flags apply only to the \'CC51\' element type produced
for cloud coverage prior to June 1951.

> B The 0 found in byte 5 of CC51 should be a \'b\' = thin obscuration.
>
> \- The 0 found in byte 5 of CC51 should be a \'-\' = total
> obscuration.
>
> \* The 0 found in byte 5 of CC51 should be a \'\*\' = original value
> invalid.
>
> 9 The digit found in byte 5 of CC51 (low clout amount)is a valid code.
> See Pre-6/51 Cloud Cover Table for Element \'CC51\".

**3. [Start Date]{.underline}:** Military stations provided most of the
early observations for archiving from 1941 through June 1948. Major
changes in observing and recording practices during 1948 represent the
primary basis of digital information for all the principle reporting
stations residing in this data set. ASOS stations began reporting in
September 1992.

**4. [Stop Date]{.underline}:** Ongoing.

**5. [Coverage]{.underline}:** U.S.A., Caribbean Islands, Pacific
Islands, and other overseas stations of the National Weather Service,
U.S. Navy, and U.S. Air Force.

a\. Southernmost Latitude: 90S

b\. Northernmost Latitude: 90N

c\. Westernmost Longitude: 180W

d\. Easternmost Longitude: 180E

**6. [How to Order Data]{.underline}:**

Ask NCDC's Climate Services about the cost of obtaining this data set.

Phone: 828-271-4800

FAX: 828-271-4876

E-mail: [**NCDC.Orders@noaa.gov**](mailto:NCDC.Orders@noaa.gov)

**7. [Archiving Data Center]{.underline}:**

National Climatic Data Center

Federal Building

151 Patton Avenue

Asheville, NC 28801-5001

Phone: (828) 271-4800**.**

**8. [Technical Contact]{.underline}:**

National Climatic Data Center

Federal Building

151 Patton Avenue

Asheville, NC 28801-5001

Phone: (828) 271-4800**.**

**9. [Known Uncorrected Problems]{.underline}:** Major changes have
occurred to the DSI-3280 data set which may have caused significant
biases when used in conjunction with the historical record. In September
1992, the Automated Surface Observing System (ASOS) was gradually
implemented for stations in this data set replacing the human observer.
ASOS was designed specifically to support aviation operations and
forecast activities. As a result, significant changes have occurred in
this data set for many previously observed weather parameters. For
example clouds are not observed by the ASOS ceilometer above 12,000
feet. The user is advised to carefully read the documentation for each
desired weather element in order to ascertain any possible data biases
that may have been introduced in the historical record as a result of
ASOS.

On July 1, 1996, another significant change occurred, which involved the
operational transmission of hourly surface observations. On this date,
the United States implemented the International METAR transmission
format code, replacing the long standing Surface Airways Observation
(SAO) code. The METAR code requires different format procedures for
transmitting basic weather observations. For example, cloud amounts are
transmitted in eights as opposed to tenths and temperature is
transmitted in Celsius as opposed to Fahrenheit. There are many other
differences, both major and minor. Again, the user is advised to
carefully read the documentation for each desired weather element in
order to ascertain any possible data biases that may have been
introduced in the historical record as a result of the METAR code
change.

**10. [Quality Statement]{.underline}:** Quality of the Surface Airways
Hourly data is considered quite good. All observations have received
some form of quality control measures depending on the agency and the
years of collection. During the early years this was almost entirely a
manual effort. As more sophisticated techniques of processing were
introduced, the quality control procedures were also improved.
Generally, quality has improved throughout the period of record.
Beginning with the data for January 1984, the surface airways hourly
observations were processed through a completely revised system. Relying
heavily on new computer editing procedures, data are subjected to
internal consistency checks and compared against climatological limits.
See EIS C-2.

The automated recording of surface observations began in September 1992
with the implementation of ASOS. The ASOS data receive various types of
quality control at the station. For example, pressure is quality
controlled by use of redundant sensors. If one or more of the six
samples read each minute from one pressure sensor is missing, only the
remaining sensors are used to determine the pressure. Sensor values for
the same minute may not differ by more than 0.04 inches. The lowest
pressure reading that does not differ from the other sensor readings by
more than 0.04 inches mercury is considered the observed pressure.
Discussion of quality control procedures for other sensors may be found
in the [ASOS USER\'S GUIDE]{.underline}. The quality control flags are
hand checked in this data set, where as, DSI-3283, ASOS Surface Airways
Hourly Observations, the quality control is fully automated.

**11. [Essential Companion Datasets]{.underline}:**

The use of NCDC's Station History file (DSI-9767) is required to
determine metadata on each station (name, location, elevation, etc.).
This can be accomplished by comparing the station number in bytes 4
through 11 of this data set with the corresponding station number in the
Station History data set.

Station History Locations are known to the nearest minute of latitude
and longitude. ASOS provides location to the nearest second.

**12. [References]{.underline}:**

> National Weather Service, August 1991: [ASOS USER\'S
> GUIDE]{.underline}, NOAA-NWS, Silver Spring, MD.
>
> Environmental Information Summary C-2, [Local Climatological
> Data]{.underline}, National Climatologic Data Center (NCDC).