# Presentation: 404810

## LAB 2

- SURFACE OBSERVATIONS

- NAS  125

## DCA  SA  1950  20 SCT 55 OVC  8  S-  

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- BWI  SA  1950  CLR  10  371/19/2/2710G19/062

- ??????????????????????????????

## Virginia Stations

- DCA – National Apt		LYH - Lynchburg
- IAD – Dulles Apt                     	DAN - Danville
- DAA – Fort Belvoir                 	AVC – South Hill
- NYG- Quantico                       	WAL – Wallops I.
- CHO – Charlottesville 		RIC - Richmond
- SHD – Staunton   		ORF - Norfolk
- ROA – Roanoke                      	NTU – Ocean NAS
- FAF- Ft. Eustis                          	LFI – Langley AFB
- PHF – Newport News             	LNP - Wise

## TIME

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**TIME**

- UTC =  EST + 5

- 1950 = EST + 500
- 1450 = EST
- 2:50 PM = EST

- What if UTC=1357 ?

- 1357 = EST + 500
-  857  = EST
-  8:57 AM = EST

## CLOUDS

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**CLOUDS**

- SCT = scattered clouds           BKN = broken clouds
- OVC = overcast                	       X    = obscured
- CLR = clear

- Leading number is height of cloud base in hundreds of feet

- 20 = 2000 feet            55 = 5500 feet          1= 100 feet

## DCA  SA  1950  20 SCT 55 OVC  8  S-  

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- This is prevailing horizontal visibility in miles.

- Here, it is 8 miles.

- 1⁄2   means one half of a mile

**VISIBILITY**

## DCA  SA  1950  20 SCT 55 OVC  8  S-  

- DCA  SA  1950  20 SCT 55 OVC  8  S-
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## SEA LEVEL PRESSURE

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**SEA LEVEL PRESSURE**

- Sea level pressure values typically
-     range from 980-1050 mb

- Leading 9 or 10 is left off, so if value starts with 0-5,
-    add a 10 in front.   if value starts with 6-9, add a 9.

- 253=1025.3 mb

- Place a decimal point in front of the last number

- 998.5 mb

- 985=

- 090=

- 1009.0 mb

## DCA  SA  1950  20 SCT 55 OVC  8  S-  

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- 1st number is temperature, 2nd is dew point
-         in degrees Fahrenheit

- T = 22°F

- Td = 20°F

**TEMPERATURE / DEW POINT**

## DCA  SA  1950  20 SCT 55 OVC  8  S-  

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- 1st number refers to wind direction;
-           2nd refers to wind speed

- Multiply 1st number by 10 for direction

- 07*10=70 degrees=EAST NORTHEAST

**WIND**

- 11 = 11 **knots**

- G at end means GUST
-    G17 means gusts to 17 kt

- 2720=

- West wind at 20 kt

- 0000=

- Calm winds

-  VR02 = variable direction at 2 kt

## Slide 11

## ALTIMETER SETTING

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**ALTIMETER SETTING**

- Altimeter pressure values typically
-     range from 28-31” Hg

- Leading 2 or 3 is left off, so if value starts with 0 or 1,
-    add a 3 in front.   if value starts with 8 or 9, add a 3.

- 027=30.27” Hg

- Place a decimal point two places from the end

- 29.43” Hg

- 943=

- 156=

- 31.56” Hg

## SPECIAL COMMENTS

- SNB46 = snow began at 46 minutes past the hour
- RAE13 = rain ended at 13 minutes past the hour
- WSHFT 1943 = wind shifted direction at 2:43 PM EST
- PK WND 1819 = peak wind occurred from the south    at 19 kt during the past hour
- PRESFR = pressure falling rapidly
- SNICR 1/3 = snow on ground increased by 1 inch during the past hour;  3 inches now on the ground
- FQNT LTG DSNT SW = observer sees frequent lighting in the distance in the southwest direction
- P0008 = .08” of precipitation fell within the past hour
- VIS NE 2 = visibility is 2 miles in the northeast quadrant

## BWI  SA  1950  CLR  10  371/19/2/2710G19/062

- BWI Airport  Standard Observation at 2:50 PM EST

- Clear skies with visibility at 10 miles

- Sea level pressure is 1037.1 mb

- Temperature is 19°F;   Dew point is 2°F

- Wind is from the west at 10 kt with gusts to 19 kt

- Altimeter setting is 30.62” Hg

## Slide 15

## Slide 16

## Slide 17

## 29

- 28

- 098

## Slide 19

## Slide 20

## Slide 21

## * *

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- Let’s plot our original examples

- 253

- 22

- 20

## 371

- 19

- 2

## Slide 24