700 MB. MAP (10,000 FT.) Click to print in a new window
How do I read the map above and what does it all mean? First of all, this is a computer 700 MB.model forecasting future weather. In this case, it is forecasting the weather 48 hours in advance. The forecast is valid 12/26/2009 at 06UTC. How do we know this?
At the bottom of the map see:
12/24/09 06 UTC 048 HR FCST VALID 12/26/09 06 UTC NCEP/NWS/NOAA.
This is what the numbers mean.
12/24/09 06UTC = the date and time the map was produced.
048HR FCST= this indicates how many hours out the forecast is valid. (48 hours)
VALID= SAT 12/26/09 06 UTC. This map is valid for 10/29/2009 at 06 UTC.
NCEP, NEW, NOAA= list the branches of the government responsible for the forecasts.
The 700 MB. Map represents a level in the atmosphere of about 10,000 ft. above sea level.
WHAT DO WE SEE? It looks very much like the 500 MB. Map with the ridges along the west coast and just off the eastern part of the United States. It shows the numbered solid lines that were present on the 500 MB. Map. Notice, however, THE SHADES OF GREEN on the map. The green represents the relative humidity (moisture) in the atmosphere. LIGHT GREEN indicates a relative humidity of 70% whereas the darker green color represents a relative humidity of 90%. A relative humidity of 70% generally indicates cloudy weather with a few rain or snow showers depending on the season. It could also indicate some steady light or very light precipitation. A relative humidity of 90% generally indicates cloudy weather with a steady area of precipitation, which possibly could be heavy. Precipitation generally begins when the 700 MB. Map indicates the relative humidity is increasing from 70% to 90%. This, of course, is a very general rule.
HOW MUCH MOISTURE IS PRESENT IN THE UPPER AIR?
(700 MB. MAP (10,000 FT.)
NOW LET’S TRY SOME REAL TIME WEATHER FORECASTING.
Click on this: http://www.nco.ncep.noaa.gov/pmb/nwprod/analysis/
1. CLICK ON www.nco.ncep.noaa.gov LINK ABOVE. 2. CHOOSE MODEL-GFS 3. SELECT UPPER AIR PARAM.- 700_rh_ht 4. CHOOSE FORECAST HOUR- 000 5. CLICK ON THE "NEXT" BUTTON, THE MAP WILL ADVANCE 3 HOURS, CLICK NEXT AGAIN, THE MAP WILL ADVANCE ANOTHER 3 HOURS.
1. Go back to the original page. (Model Analysis & Forecasts) GFS
2. HOW MUCH MOISTURE IS IN THE AIR? If you want to see how much moisture is in the air, go to the 8th column from the left (700 mb. RH, Ht) The 700 mb. map is approximately at a height of 10,000 feet. Times are listed on the left (000-018) etc.
3. ONCE AGAIN DO YOU SEE THE SOLID LINES? (HEIGHT LINES) AND WIND BARBS? The tighter the lines are packed, the stronger the winds.
4. DO YOU SEE 2 SHADES OF GREEN? The light shade of green indicates a relative humidity of 70%. Generally an area with 70% INDICATES MOSTLY CLOUDY SKIES WITH THE CHANCE OF A FEW SHOWERS. The areas with dark green indicate a relative humidity of 90%. Generally, an area with 90% indicates cloudy skies with precipitation. (rain or snow). *PRECIPITATION USUALLY BEGINS WHEN YOUR LOCATION IS AT 70% INCREASING TO 90%. (RELATIVE HUMIDITY ABOUT 80%).
5. From the “GFS” YOU WILL BE ABLE TO FORECAST THE WEATHER OUT 384 HOURS FOR YOUR AREA OR ANY AREA IN NORTH AMERICA. TRY IT! All the rules given to read the NAM apply to the GFS. The NAM , however, is sometimes more accurate for short term forecasts. (Next day). However, it is best to look at both the NAM and the GFS when making a forecast