METR 361                                                                                                                  Spring, 2018

Exam 2                                                

 

Directions: This is an Open-notes exam.  Use anything you want, including the Internet.  You can’t ask each other questions but you can ask me for clarifications (no guarantee that I’ll be able to answer). Answer all parts of all questions in the blue books (except when directed to draw on a map) or write a txt or odt file and send to Jerome.Blechman@oneonta.edu.

 

 

1. This question is about the atmosphere over Fort Worth, TX (KDFW), as shown by their morning sounding.

            a. ( 15%) What about this sounding shows a favorable pre-storm environment for severe thunderstorms later in the day?  I’m not asking if the severe weather actually occurred later.  Instead, identify five aspects of the pre-storm environment that would support the later development. You must also briefly indicate what each feature does to make the atmosphere favorable for severe thunderstorms. Do not cite any of the indices. That’s part b.  Also, it’s hard to read the winds so I’ll disclose the maximum wind below 600 mb is at 850 mb and it is 19550 in dddff format.

            b. ( 8%) Based on the indices shown at the top of the sounding, assess the potential for severe thunderstorms as shown individually by the Lifted Index, Total-Totals Index, SWEAT Index, and CAPE.  For each index as shown, write down the value (including units where applicable) and choose one of the following for a risk of severe weather indicated by that one index: None, Marginal, Slight, Moderate, High.

            c. (  5%) What is the LCL of surface air?

            d. (  5%) If the 12Z air at KDFW is lifted by some means other than heating, at what level will that air parcel reach its LFC?

            e. (  4%) What is the convective temperature in Celsius degrees?

            f. (  6%) Suppose the air temperature reaches the convective temperature that you found for part e.  What will happen to a surface air parcel and why will it happen?  Do not assume anything about the weather map, such as fronts.

            g. ( 5%) Based on this sounding, what could happen (or fail to happen) in the vicinity of KDFW that would result in no severe thunderstorms and, in fact, no thunderstorms at all?  Your answer must be meteorologically reasonable, i.e., you can’t speculate that a 100-mile wide alien spacecraft settles over the city or anything else that is fantastic or impossible.

 

 

2. For this question, review the following NAM forecast products:  MSLP/2 m temperature, 850 mb heights/RH, 700 mb heights/RH, 500 mb heights/vorticity, 300 mb, and 200 mb.

            a. (24%) Find one feature that is favorable for severe thunderstorms on each of the maps listed above. They may involve the same meteorological measurement, like wind on different maps. To report these, on the blank U.S. map marked Composite, draw a symbol or series of symbols that represent the favorable features you found.  At the bottom of the map, provide a key to what each symbol means.  You may use color but it is not a requirement if each feature has a unique symbol.

            b. ( 8%) On the blank U.S. map marked Convective Outlook, draw a day 1 categorical outlook based solely on your Composite Chart from part a. Unlike the SPC Convective Outlook, yours is only for 06Z which is the verifying time of each of the maps. Use the standard SPC nomenclature and color fills.  This one does require colored pencils.  Do not use ink. 

            c. ( 8%) Your Convective Outlook must have a probability assessment written in (SLGT, MDT, etc.). Using the map features you chose, explain how you decided on the probability and on the locations of the boundary lines between areas.

 

3. Last Friday (April 6), a line of heavy thunderstorms passed through the state of Arkansas, as shown on the radar loop.  Surface observations showed several reports of thunderstorms, mainly in the center and southern parts of the state.  In the north, stations such as KARG, KCCA, and KFLP are reporting clear or almost clear skies.  Yet, the satellite loop shows plenty of clouds.

a. ( 7%) What is happening that those stations and several others in Arkansas are reporting CLR when there are clouds in the sky?

b. ( 5%) There is one station on the surface plot map that is reporting some weather element that no machine is currently able to observe so you know that a human observed it.  What is the three-letter designation for the station and what is the weather element being reported?   Note that the three-letter designations are shown in grey to the lower right of the station circle.