CWS 4A

3D"{short

TEMPERATURE AND AIR MASS ADVECTION

Do Now:

Print this file.
Print the associated Curr= ent Weather Studies A Image 1 File.
Print the Daily Summary and/or Supplemental Information Files, if directed by your instructor.=

To Complete Investigation:

Reference: Chapter 4 in t= he Weather Studies textbook.
Complete Investigation 4A= in the Weather Studies Investigations Manual as directed by your instructor.
Complete this Monday online-delivered Current Weather Studies 4A activity if directed by yo= ur instructor.

As noted in the Monday Daily Weather Summary for 28 September 2009, two storm systems with their accompanying precipitation areas affected the east= ern and north central portions of the country at the end of the weekend. Follow= ing the persistent rains across the Southeast for the past week, the movement of the systems signifying more active weather patterns was welcomed. Those movements, however, also brought relatively rapid changes of temperature for the locations over which they passed.

Image 1 is the map of plotted station models with reported surface weather conditions (Isotherms, Fronts, & Data) for 11Z Monday, 28 SEP 2009 (7 AM EDT, etc.). Note that on this Image 1 map, the= isopleths are isotherms (not isobars). The H and L centers and fron= tal positions are shown as of 09Z on the map.

1= . From a Low shown centered north of Vermont and New Hampshire, one system with a short occluded front (purple with half circles and triangles on the same si= de) connected to a cold front that arced southeastward off the Atlantic coast to become stationary over central Florida and extend into the eastern Gulf of Mexico. From the northern extremity of the cold front, a warm front pointed eastward into the Atlantic. This meeting= of occluded, cold and warm fronts is termed a triple point. Such patter= ns frequently mark the completion of the life cycle of mi= dlatitude storm systems.

A second Low was shown with its center over <= st1:place w:st=3D"on">Lake Superior. From that Low a short occluded front curved southeastward to Lake Erie. From = Lake Erie the frontal system curved around over the O= hio River Valley, t= he lower Mississippi River Valley, northern Texas and finally ended in <= st1:place w:st=3D"on">New Mexico. That frontal boundary from= Lake Erie to New Mexico was shown as a [(warm)(co= ld)(stationary)] front.

2= . The winds at stations in the several-state area about the Great Lakes L displayed a circulation that was general= ly [(clockwise)(counterclockwise)] and inward. This circulation was bringing cool air southward from Canada to the north-central p= ortion of the country.

3= . Des Moines, Iowa,= Kansas City, Missouri and Wichita, Kansas were all located near the the [(30= )(50)(70)] degree Fahr= enheit isotherm and have temperatures within a few degrees of the isotherm's value. The isotherm label was located on the line in eastern Kansas. Highlight this isotherm from i= ts position at the Canada-Minnesota border to New Mexico.

4= . Des Moines had wi= nds plotted as 15 knots from the [(northwest)(northeast)(southwest)(southeas= t)] at map time.

5= . Generally, the winds at all three stations exhibited flows that were directed across t= he isotherm at large angles. Wich= ita's winds was essentially perpendicular to the isoth= erm line. These wind directions were from [(higher toward lower)(lower toward higher)] temperature regions. Stations from the Dakotas around to north <= st1:place w:st=3D"on">Texas generally displayed this temperature-wind flow directional pattern.

6= .      Therefore, the wind flows across the isotherm at Des Moines, Kansas City and Wichita demonstrated that [(co= ld)(warm)] air advection was occurring= in this region.

7= .      This advection pattern was "behind" (to the west and north of) the = [(cold)(warm)] front.

8= .      One would conclude then that air motions and temperature patterns following a c= old front would produce [(cold)(= warm)] air advection.

9= .      By contrast, Atlanta, Georgia and Pittsburgh, in western Pennsylvania, had winds that were gene= rally from a southwesterly direction. This flow was [(behind)(ahead of)] the cold front.

1= 0. Atlanta and Pittsburgh were on opposite sides of the looping [(40)(50)(60)] degree Fahrenheit isotherm (labelled along the = SC-GA border).

1= 1. From = the isotherm and the direction of winds at Atlanta and Pittsburgh, [(cold)(warm)] air advection was occurring ahead of the front. Buffalo, New York and several other stations along the Gulf coast also had this pattern of air advection.

1= 2. As the frontal system advances eastward and southward, stations ahead of the front= can expect temperatures to [(rise)(fall)] wh= en the front passes their location. The advance of the cooler air is suggested= by the sequence of temperatures shown from Dallas (73 °F) to Oklahoma City (64 °F) t= o Wichita (52 °= F).

As we advance into the fall season, successive pushes of cooler air will occur and temperatures will fall with cold-air advections bringing hints of= the winter to come. Also, decreasing daily doses of sunshine will allow the gro= und to cool. Fall color changes remind us of those shortening days and changing seasons.

Critical Thinking and Diversity Component: The Week 4 Critical Thinking/Diversity Component, located in the Learning Files section of the course homepage, applies the skill of explanation and the attribute of reasoning with confidence to the critical thinking activity of factors determining temperature and to the diversity component concerning the fate = of Greenland's Viking and Inuit settlements.

If directed by your instructor, place the answers to Investigation 4A and Current Weather Studies 4A on the A Answer Form linked from the AMS Weather Studies website.

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