WELCOME BACK: Procedure continued from STUDY GUIDE.
As detailed in the first part of this activity, clouds and precipitation are commonly found along fronts, on the upward branch of convection currents, along the windward slopes of mountain ranges, and where surface winds converge. Often the most expansive area of precipitation forms in association with fronts.
Examine Image 1 from the Monday 06 October Activity 5A. Precipitation, as shown by the radar echoes, was occurring in association with [(the cold front along the East Coast) (the high pressure area centered in Central Oklahoma)]. Clear skies and no precipitation were found near [(the cold front along the East Coast) (the high pressure area centered in Central Oklahoma)].
Over the previous weekend, 20 - 21 October 2001, a front slowly moved southward from the Prairie Provinces to the mid-Mississippi Valley while weak low pressure was situated in Southern California and Montana and another storm was moving into the Pacific Northwest coast. Heavy rain persisted across the southern half of the Florida Peninsula in association with an old stationary front, shown as a dashed line low pressure trough, that had lingered over the region for nearly a week. Details of this weather pattern can be found in the Monday, 22 October, Daily Weather Summary.
Image 1 is the surface weather map for Monday morning, 12Z 22 OCT 2001. The major map feature in the Northeast was a [(warm) (stationary) (cold)] front that extended from New Brunswick to western Pennsylvania. The front continued across the Midwest and mid-Mississippi Valley as a [(warm) (stationary) (cold)] front.
The presence of precipitation on the surface map is indicated by radar echoes as areas of gray shading (colored, when viewed on screen). The intensity coding scheme is given at the lower left edge of the chart. The major area of precipitation at 12Z 22 OCT 2001 associated with the fronts described above was located from [(southeast Nebraska to western New York) (Oklahoma to Virginia)]. As indicated by the surface winds from Texas to Kentucky, the relatively warm, humid air that was lifted along the front produced precipitation. This airlikely advected (flowed) from [(south central Canada) (the Gulf of Mexico)].
Wind directions in North Dakota at 12Z 22 OCT 2001 were generally from the east and southeast. This was consistent with the general [(counterclockwise) (clockwise)] flow pattern around the low-pressure areas centered in extreme southwestern Saskatchewan and southeastern Montana. In this general area the elevation of the Earth's surface increases from east to west. The resulting upslope flow focused light precipitation along the [(North Dakota-South Dakota) (North Dakota-Saskatchewan-Manitoba)] border.
Precipitation scattered from northern California to southeastern Washington was also in association with the low pressure circulation in mountainous terrain. Although precipitation was light to moderate at this time, precipitation intensity is expected to increase as [(the storm system) (high pressure)] off the coast is forecast to move into British Columbia and Washington State by Monday afternoon to evening.
Image 2 is the Stüve diagram at Miami, Florida from 12Z 22 OCT 2001, the same time as the surface map. The troposphere at this time is generally [(far from saturation) (near to or at saturation)] indicating that clouds were likely [(present) (not present)]. The Image 1 surface map shows that precipitation [(was) (was not)] occurring in and around Miami at this time.
Image 3 is the 24 Hour Precipitation map for the period ending at 12Z on Monday, 22 OCT 2001. Significant precipitation reports (0.1 inch or more) are located in association with fronts in the eastern United States, in the Northwest, and across southern Florida. The greatest amounts of precipitation were reported in [(western New York) (south Florida)]. This was due to the slow-moving nature of the storm system.
Have your students view local radar displays from weathercasts and reports of precipitation amounts when rainfall occurs in your area. Compare your reports with DataStreme weather maps to see what weather conditions are probably causing precipitation in your area.
Hold this activity until you have completed all applications for this week. Instructions for faxing your LIT mentor will appear at the end of this week's Activity B.
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