AEROGRAPHER'S MATE 3 & 2 



WIND SPEED 

 TYPE OF 

 MIDDLE CLOUC 



WIND DIRECTION 



TEMPERATURE 



PRESENT WEATHER 



BASE HEIGHT 

 OF LOW CLOUDS 



BAROMETRIC PRESSURE 

 REDUCED TO SEA LEVEL 



PRESSURE HIGHER OR 

 LOWER THAN 3 HOURS AGO 



AMOUNT OF BAROMETRIC 

 CHANGE IN LAST 3 HOURS 



BAROMETRIC TENDENCY 

 IN LAST 3 HOURS 



TIME PRECIPITATION 

 BEGAN OR ENDED 



THE WEATHER DURING 

 PAST 6 HOURS 



AMOUNT OF LOW 

 CLOUDS 



AMOUNT OF PRECIPITATION 

 DURING PAST 6 HOURS 



209.298 

 Figure 11-1. — Synoptic station model — land sta- 

 tion. 



charts rests with each weather unit. The charts 

 are ordered from the applicable Defense Map- 

 ping Agency Aerospace Center (DMAAC) outlet 

 in accordance with instructions on the procure 

 paga of the latest edition of the Catalog of 

 Weather Plotting Charts (NW 50-1G-518). 



Surface charts are normally plotted every 

 6 hours from the synoptic observations of 0000, 

 0600, 1200, and 1800 GMT. (For communica- 

 tion purposes the latter "Z" has been assigned 

 as a short designator for GMT.) 



The name of the station, date, time, plot- 

 ter's initials, decoder's initials, and name or 

 initials of the analysts should be entered on 

 EVERY weather map. ALWAYS REMEMBER IN 

 METEOROLOGY THAT ANY MATERIAL WITH- 

 OUT A TIME AND DATE IS PRACTICALLY 

 USELESS. 



The plotting of simultaneous (synoptic) weather 

 reports enables the forecaster to obtain a more 

 comprehensive "picture" of the existing weather 

 conditions for a given period of time over 

 a large area. When the weather map has been 

 completely plotted, it is analyzed for forecasting 

 purposes. This aids the forecaster in his pri- 

 mary duty, which is the preparation and issuing 

 of weather advices and forecasts. 



Plotted Surface Data 



The basic data plotted on surface synoptic 

 charts are the land and ship station surface 

 synoptic reports. Our concern here is with the 



information plotted on the surface chart and its 



use. 



Land station or ship station synoptic obser- 

 vations are encoded in accordance with instruc- 

 tions contained in FMH No. 2. Synoptic Code 

 (NA 50- ID- 2) or International Meteorological 

 Codes (Year) Worldwide Synoptic Broadcasts 

 NA50-1P-11. Normally, only the first five groups 

 and the 7-indicator group of the land station 

 synoptic report are entered on the surface chart 

 as illustrated in figure 11-2 (A). 



For ship reports, the use of groups is a 

 little more complicated. A station circle is drawn 

 at the place indicated by the two position groups. 

 The meteorological information is plotted next. 

 This information is found in the remaining 

 groups of the code. Ordinarily, the plot in- 

 cludes the wind group, the weather and visi- 

 bility group, the pressure group, the cloud 

 group, the pressure tendency group, the sea 

 temperatuve/dewpoint group, and the wave group, 

 as shown in figure 11-2 (B). Ship plots are 

 complicated by the fact that three types of 

 reports are usually available from them — the 

 full form, the short form, and the abbreviated 

 form. The short form and the abbreviated form 

 do not contain all the meteorological informa- 

 tion that the full form contains. A specific 

 weather office may have need for all the infor- 

 mation transmitted in both the land station and 

 ship reports. Perhaps the need may apply only 

 to certain elements like the rain group, or to 

 ice information; possibly the needs are only 

 temporary. In such cases the additional infor- 

 mation is plotted and analyzed. 



LAND STATION CODE PLOTTING. — There 

 are many variations to the synoptic code. The 

 difference in most cases is small, but very 

 important. Be sure to check the WMO Region 

 in which you are stationed or operating for 

 the differences in the code that is employed 

 in your area. The synoptic code format was 

 given in the previous chapter. The U. S. land 

 station plotting model for the code is shown in 

 figure 11-1. 



In general, the data contained in a synoptic 

 report is plotted around the station circle in 

 a counter-clockwise manner, beginning with pres- 

 sure. This is the easiest method; however, if 

 you can plot in an easier order, use it. The 

 important thing to remember is to plot in the 

 same order all the time to avoid missing 

 elements. 



194 



