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Activity C: INTERPRETING SURFACE WEATHER MAPS Educational Outcomes: What is the weather now? What is the weather going to be in the next few hours? Weather is the state of the atmosphere at a particular time and place, mainly with respect to its impact upon life and human activity. It is defined by the various weather elements including air temperature, humidity, cloudiness, precipitation, visibility, air pressure, and wind speed and direction. The surface weather map is a useful too! for depicting weather conditions over broad areas. Decode the symbols appearing on a surface weather map and describe weather conditions at various locations on the map. Identify fronts appearing on the map, the weather differences likely to be occurring on either side of a front, and the motions of fronts. Describe general relationships between wind patterns and the high and low air pressure centers shown on weather maps. Investigations: 1. Examine the surface weather map presented in Figure 1 of the narrative section of this guide. The weather map symbols shown are those commonly seen on television and in newspapers- The H's and L's identify centers of relatively high or low air pressure compared to their surroundings. Moving outward horizontally from the I_ located in lower Michigan, air pressure [(tV/trc't/x'v > (ili-creases)]. Moving outward horizontally from the H positioned in Texas, air pressure [(i/HTt'i;vr.v > (ffarreases)]. 2. The thick curved lines on the map are air mass boundaries. In the atmosphere, broad expanses of air with generally uniform temperature, humidity, and density come in contact with other masses of air having different temperature, humidify, and density. Because air masses of different densities do not readily mix. the boundaries separating air masses tend to remain distinct. These boundaries, called fronts, typically separate warm and cold air. The leading edge of advancing cold air is a cold front and . as shown in the lower pan of Figure !, is signified by spike symbols which are pointing in the direction toward which the cold front is moving. The leading edge of advancing warm air is a warm front and is signified by semi-circles on ihe side of the front's movement. The front in the Southeastern US is a |(cold) (warm)] front. According to (he map, persons living in South Carolina can expect {(colder) (warmer)} weather otter the front passes. ;cipitation is depicted on maps by a variety of symbols including dots or periods for tin} (snow)], stars or asterisks for \(rain} (snow)], horizontal lines for _, and t 4. Some weather maps display weather conditions at individual weather stations by the use of a station model. In the model, weather is plotted in, on, and around a circle representing the station. The following plotted station model shows where and how various weather elements are reported: 75 023 a. Temperature (at the ''1 1 o'clock" position): __ _°F. b. Dewpoint (at the ''8 o'clock'' position): _ °F. c. Wind direction is shown by the "arrow" shaft drawn into the circle representing the station. Unless otherwise noted, north is to the top on the map and east is to the right. Wind is always named for the direction from which it blows. In the above depiction, the wind direction is __ __ . d. Wind speed is rounded off to the nearest 5 knots (1 knot equals 1 .2 miles per hour) and is symbolized by "feathers" drawn on the clockwise side of the wind-direction shaft. A full feather represents 10 knots and half feathers indicate 5 knots. A pennant indicates 50 knots and a circle drawn around the station circle signifies calm conditions. In this case, the reported wind speed is __ knots. e. Air pressure (adjusted to sea-level) is reported as a coded number to the nearest tenth of a millibar (mb). To decipher the plotted pressure value (reported at the "1 o'clock'' position), first place a decimal point between the second and third number from the left. Then add a "9" or "10" to the left so that the resulting number falls within the range of air pressures that could occur at sea level (usually between 960 mb and 1050 nib). For example, a plotted value of 126 represents 1012.6 mb and 863 denotes 986.3 mb. The air pressure reported above is _ mb. f. Sky coverage (total amount of cloud cover) is reported inside the station circle. An empty circle indicates no cloud, a half-shaded circle means five-tenths of the sky y is cloud-covered, and a fully shaded circle stands for a completely overcast sky. Th reported cloud cover is __ . g. Current weather is plotted at the "9 o'clock" position using a variety of symbols representing the particular weather conditions. The reported current weather is ,t map time the conditions in Little Rock, Arkansas were: temperature ewpoint F. air pressure _ millibars, cloud coverage _ _ degrees and 7. Examine the current DataStreme Atmosphere surface weather map given to you. The dat. of the map given to you is _ . Describe the weather conditions reported at the station nearest where you live. How do these compare to the conditions al surrounding stations? 8. Describe the general pattern of weather conditions across the country at map time. OOZ Fronts at OOZ 02 OCT 2004 NATIONAL 2 KM BASE REFLECT 0,00 DEG Blue - Isobars (4 mb) MONITORING THE WEATHER 3 9) Using the map in Figure 1 and the color codings above the symbols, trace over the map symbols with the correct colors and shade in the precipitation areas. Then, plot the information on the station models. STATION MODEL NUMBER: 1) Cloudy. Rain shower, Temp: 45°, Dew point: 44°, Wind: 330° at 1 Omph, Press: 1002.0mb 2) Pt. Cloudy, Temp: 65°, Dew point: 54°, Wind: 130° at ISmph, Press: 1000.0mb 3) Mo. Cloudy, Temp: 48°, Dew point: 40°, Wind: 270° at lOmph, Press: 1008.0mb 4) Sunny, Temp: 60 , Dew point: 40°, Wind: 210° at lOmph, Press: 1015.0mb 5) Mo. Sunny, Temp: 75°, Dew point: 25°, Wind: 100° at 20mph, Press: 1022.0mb 6) Pt. Cloudy, Temp: 65°, Dew point: 54°, Wind: 350° at 15mph, Press: 1030.0mb 7) Cloudy, Snow shower, Temp: 25°, Dew point: 24°, Wind: 330° at 25mph, Press: 995.0mb 8) Pt. Cloudy, Temp: 35°, Dew point: 32°, Wind: 100° at lOmph, Press: 1000.0mb 9) Mo. Cloudy, Temp: 33°, Dew point: 28°, Wind: 280° at 20mph, Press: 1010.0mb Weather Map Symbols CLOUD SYMBOLS FOUR BASIC FORMS ( CIRRUS u r* ?O,000 It. to ten milei high. Feathery curves, ma/es tails. CUMULUS Q 2.5OO (eel to one mila high. Heaped up. Fairer weather. STRATUS Sea level to 2,000 led high. Layered, misty, thm, loglike. Sample Station Plot ~~~"~~ Wind' / \ 1 \J ^< / 57 \ 107 NIMBUS - Rain clouds lower In tho sky and (dining with a Stratus or * Cumukis rnaw. wealher > *f ( ) _§\ 56 ^ TYPICAL. COM8INATSONS CIRROSTRATUS *CIRROCUMULUS - ^ ALTOSTRATUS - £ ALTOCUMULUS £ CUMULONIMBUS S STRATOCUMULUS - ~^~ NIMBOSTRATUS - & / DewPoint(F) 35t? \ \ \ \ Pressure trend (mb)Sky cover NOTE: Multiple rain or snow symbols indicate intensity, i.e. light (2 symbols), moderate (3 symbols), heavy (4 symbols) Wind Sky Cover O clear O Calm 9m Sea-lsvel pressure' 1-2 knots (I -2 mph) Fronts apd Radar cold front ,, blue warm front "* C^scaltered ' 3-7-knots(3-Smph) stationary front ^TLlTe d>m \ occluded front ^j rp ie 9 4/8 'N 8-l2knots(9-]4mph) 13-17knots(15-20mph) Selected Weather Symbols . .srt&n V Rain Shower JK'1 P-^ct Thunderstorm Drizzle trough °T"j ""i™ SnOW (see note belov,) * » 5/8 ® broken GrfAS\ ^ ]8-22knots(21-25mph) squall line * V Snow Shower ^ 23-27 knots (26-3 1 mph) dryline Jf^^n C^O Freezing Rain Red ^\ 28-33 knots (32-35 mph) O7/8 Smoke ^^ Freezing Drizzle ^\ 33-37 knots (36-41 mph) W\ 38-42 knots (42-45 mph) •overcast \\\\\ ~ S Dust or Sand ~Fog " Blowing Snow ^Haze"" " 43-46 knots (46-52 mph) ^ 47-52 knots (53-61 mph) G$ obscured ^1 53-57 knots (62-66 mph)