# Presentation: 376490

## ANALYSIS OF UPPER AIR CONSTANT

***ANALYSIS OF UPPER AIR CONSTANT***
***PRESSURE SURFACES!***
***REFERENCE***
***INTRODUCTION TO FORECASTING***
***VOL. 2 ATMOSPERIC ANALYSIS***
***AG1(AW) M. BUTCHER***

## LEARNING OJBECTIVES:

***LEARNING OJBECTIVES:***

***1.  Recognize plotted data on standard upper***
***     ******air charts***
***2.  Stress concepts and rules on analysis***
***     ******of upper air parameters to help prepare***
***     ******students for the ITF course and C-school.***

## Constant pressure charts are used in conjunction with surface

**synoptic charts for the following:**
**-  Determine the movement of weather systems**
**-  Determine cyclonic and anticyclonic wind circulation**
**-  Help define air masses**
**-  Locate moist and dry areas**
**-  Aid in forecasting formation, intensity, and dissipation of **
**    ****weather systems**
**-  Determine the slopes of fronts**
**-  Determine the vertical extent of pressure systems**

## Plotted data on constant pressure charts:

**The meteorological data displayed in upper air reports are**
**generally obtained at 0000 and 1200 GMT (or Zulu) from**
**radiosonde and rawinsonde observations.  Other types of reports,**
**such as aircraft and satellite derived data are included when**
**available.**
**Although constant pressure charts can be prepared for any of**
**the mandatory levels, the most common charts  are:**
**850mb (approx 5000ft)                 700mb (approx 10000ft)**
**500mb (approx 18000ft)               300mb (approx 30000ft)**
**200mb (approx 34000ft)**

## TYPICAL UPPER AIR STATION MODEL

**TT**

**DD**

**hhh**

**hchc**

**TYPICAL UPPER AIR STATION MODEL**
**ON A CONSTANT PRESSURE CHART**

**TT= TEMPERATURE TO NEAREST WHOLE DEGREE CELSIUS**
**hhh= HEIGHT OF CONSTANT PRESSURE SURFACE IN METERS ON**
**850MB AND 700MB CHARTS, TENS OF METERS ON 500MB, 300MB AND**
**200MB CHARTS.**
**DD= DEWPOINT DEPRESSION TO NEAREST WHOLE DEGREE CELSIUS**
**hchc= 12 HOUR HEIGHT CHANGE IN TENS OF METERS**

## WIND= DIRECTION PLOTTED TO 36 COMPASS POINTS.  WHEN WIND IS

**MISSING, THE LETTER ****M ****IS PLOTTED.  WHEN WIND SPEED IS LESS THAN**
**3 KNOTS, ****LV**** (DENOTING LIGHT AND VARIABLE) IS PLOTTED.**
**- TEMPERATURES OR HEIGHTS WHICH HAVE BEEN ESTIMATED BY THE**
**ANALYSIS PROGRAM (ESPECIALLY OVER MOUNTAINOUS REGIONS AT THE**
**850MB AND 700MB LEVELS), ARE MARKED WITH A BRACKET TO THE **
**RIGHT OF THE REPORT.**
**- REPORTED VALUES WHICH ARE JUDGED BY THE ANALYST TO BE**
**ERRONEOUS ARE ALSO MARKED WITH A BRACKET TO THE RIGHT**
**OF THE REPORT.**
**- AIRCRAFT REPORTS ARE PLOTTED WITH A SQUARE AND SATELLITE**
**DERIVED DATA WITH A STAR RATHER THAN A STATION CIRCLE.**
**- THE HEIGHT IN AIRCRAFT REPORTS MAY INDICATE PRESSURE ALTITUDE**
**IN HUNDREDS OF FEET RATHER THAN THE METERS DISPLAYED IN**
**RADIOSONDE REPORTS.**

## CONTOURING CONVENTIONS

**Geopotential Height- Drawn as solid lines labeled with 3 digit**
**numbers.  **
**- 30 meter intervals on 850mb and 700mb charts**
**- 60 meter intervals on 500mb chart**
**- 120 meter intervals on 300mb and and 200mb**
**- High and low height centers are marked with an encircled ****X**
**   ****together with a large letter ****H ****or ****L****.**

## Temperature-  Isotherms are drawn with red long dashed lines at

**5C intervals-**
**Wind Speed-  Lines of constant wind speed (isotachs) are drawn**
**on the 300mb and 200mb charts with green short dashed lines at**
**20 knot intervals.  Regions of high wind speeds are enhanced**
**by alternate bands of shading and no-shading at 40 knot intervals**
**beginning at 70 knot.**

## RULES OF UPPER AIR ANALYSIS

**- Note previous position of troughs and ridges for history.**
**- Select a starting contour and sketch lightly with pencil; **
**  ****interpolate between reports.**
**- Attempt to draw contours parallel to wind flow (due to lack**
**  ****of surface friction), especially in straight line flow.  Some**
**  ****variation will occur on 300mb and 200mb charts due to strong**
**  ****winds, any curved flow, and areas of light winds.**
**- Throw out reports that are obviously in error (check reports**
**  ****around and above and below the report in question).**
**-  Use the geostrophic wind scale (located in ITF vol. 2) to smooth**
**    ****contour spacing and fill in data void areas.**

## RULES OF UPPER AIR ANALYSIS

**- Do not kink upper level trough contours; this would imply a**
**  ****front**
**- Label contours (in decameters) at the margins, and preferably**
**  ****once down the center of the chart for long contours.**
**- Label high and low height centers with ****H**** and ****L**** with their center**
**  ****values in decameters.**
**- At 500mb, ridges and highs have a warm isotherm finger or pocket**
**  ****while troughs are cold.**
**- Isotherms are drawn at 5C intervals, beginning with a value **
**  ****divisible by 5.**
**-  Ensure a higher value on one side of an isotherm and a lower**
**   ****value on the other side.**

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## 7412’s can go back to work,

***non-7412’s get out your ITF ***
***chartbooks for the hands on***
***portion.***