# Weather Maps - Jacksonville State University

Weather Maps Summary of the weather changes with the passage of a front two different air masses, so change in weather temperature varies wind direction changes wind velocity changes dew point changes barometer falls as front approaches and rises after it TOTALLY DIFFERENT AIR Much information is needed to interpret what is happening with the atmosphere.

Need to condense this information in a small space Need to show the geographic characteristics of this data Weather maps can both display this data and summarize the patterns Station Model Allows the data to be plotted in a condensed and usable format Location of the station on the map.

The name of the location or airport abbreviation might be given nearby. Temperature information in degrees Fahrenheit. Temp Dew Point Temperature in degrees Fahrenheit. Temp dewpt Wind direction

A staff is rotated around the station. Temp dewpt Remember, winds are identified as the direction FROM which they come. This would be a west northwest wind or about 290. Wind Speed Attached to the staff are symbols for speed. Temp dewpt

The coding for the wind speed symbols can be generalized as: half staff about 5 knots note, it is not on the end of the wind direction staff full staff about 10 knots these are additive for the total amounts three full staffs=30 knots

65 knots flag about 50 knots Current Barometric Pressure Temp dewpt pressure Barometric Pressure is VERY important!

average barometric pressure at sea level is 1013.25 mb. current barometric pressure is reported to the nearest TENTH BUT, they dont want to waste space average barometric pressure at sea level is 1013.25 mb. barometric pressure varies around this value + about 30 = 1043 somewhat higher 1013.3

somewhat lower - about 30 = 983 average barometric pressure at sea level is 1013.25 mb. barometric pressure varies around this value they do not PRINT the beginning number or numbers ---1013.3 13.3 x

133 they, also, do not PRINT the decimal point, but report to the nearest TENTH From the three numbers, you must INTERPRET whether the preceding value is 10 or 9

Which would make the value most realistic? add the decimal point and then consider which, a 10 or a 9 places the value NEAREST to the average pressure of 1013.25 mb. What is the pressure? (1013.3) 084

08.4 1008.4 962 96.2 996.2 281

28.1 1028.1 875 87.5 987.5 322 32.2

1032.2 Not only is the pressure itself important, but so is the way the pressure has been changing. So, more information may be given and must be coded. How has the barometer been changing? Temp

pressure trend dewpt + it is higher now than in the past - it is lower now than in the past How much the pressure has changed Temp pressure

trend change dewpt the amount of change in the past three hours again, reported in TENTHS without the decimal What has the pressure been doing? Shown diagrammatically Temp pressure

trend dewpt change shown Total amount of cloud Temp pressure trend change shown

dewpt graphic depiction of percentage of the sky covered by clouds no clouds about 60% about 10% about 75%

about 25% about 80% about 40% completely overcast about 50% sky obscured

Symbol positions to identify the cloud types high clouds middle Tempcloudspressure trend change shown low dewpt clouds

Cloud types tell much about the weather conditions. The cloud types are identified by symbols, and classed as low, middle, and high clouds. How much of the sky is covered by low and middle cloud cover? high clouds middle Tempcloudspressure trend change shown

low low or middle dewpt clouds cloud cover What amount, in tenths, of the sky is covered by low or middle clouds. This is a coded number with the percentage close to the printed number. What is the present weather? high clouds middle Tempcloudspressure

trend change shown wxnow low low or middle dewpt clouds cloud cover The current weather is very important. A detailed set of symbols provides weather descriptions. Samples of present weather symbols. rain

fog haze , * thunderstorm drizzle lightning .

snow slight rain showers ice or snow pellets cloud development not observed Combining symbols tells more of the detail. intermittent rain, slight at time of observation continuous rain,

slight at time of observation intermittent rain, moderate at time of observation continuous rain, moderate at time of observation intermittent rain, heavy at time of

observation continuous rain, heavy at time of observation 100 different symbols provide details about the PRESENT WEATHER. The visibility is especially important for pilots. high clouds

middle Tempcloudspressure trend change shown visibility wxnow low low or middle dewpt clouds cloud cover Visibility is given in miles and fractions The past weather uses symbols. high clouds

middle Tempcloudspressure trend change shown visibility wxnow low low or middle dewpt clouds PAST cloud cover , *

Time precipitation began or ended high clouds middle Tempcloudspressure trend change shown visibility wxnow low low or middle dewpt clouds PAST when cloud cover

Coded for how many hours ago the precipitation began or ended. Again, the code is close to the number of hours. Height of cloud base high clouds middle Tempcloudspressure trend change shown visibility wxnow low low or middle dewpt clouds PAST

when cloud cover base Coded height of base of clouds. Important for pilots. The amount of precipitation high clouds middle Tempcloudspressure trend change shown visibility wxnow

low low or middle dewpt clouds PAST when cloud cover base amount Amount of precipitation is plotted in inches to the nearest hundredth of an inch. Decode this station.

237 ,, 75 1 65 - 12 6 4 3

36 any low clouds? yes any middle clouds? yes 237 75 any high clouds? yes amount of low and middle clouds 6 1 12 height of cloud base 4 65 6 3

visibility 1 mile 4 36 barometric pressure 1023.7 mb trend in pressure falling pressure three hours ago 1024.9 down then how has pressure changed temperature 75 steady present weather continuous slight drizzle

dew point 65 past weather rain wind direction south when precipitation began/ended 4 wind speed 25 knots amount of sky cover 80% amount of precipitation .36 ,, -

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