METR 361                                                                                                                                                                                  Spring, 2019

Final Exam                                         

 

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). Loops are PowerPoints.  Use the arrow keys to move through the images.  Answer all parts of all 6 questions in the blue books except where you are directed to draw on the paper copies. If you like, you may instead send me (Jerome.Blechman@oneonta.edu) your electronic answers in a text, Word, or Open Office Writer (.odt) file. You have 2 1/2 hours

 

 

1. The following questions refer to a situation that occurred in the cold half of an unreported year.  You have the following guidance, all from the 12 UTC initialization of the NAM model:  Loop of MSLP/2m Temp, Single image of the MSLP/thickness initialization, Loop of 850 mb heights/temperatures, Loop of 500 mb heights/Abs vorticity, Loop of 300 mb heights/isotachs and a single image 48 hour total precipitation forecast.

 

a. ( 6%) The storm that at 48 hours after initialization is over Lake Superior was NOT an Alberta Clipper.  Give two ways that you know that from the images and loops given..

 

b. ( 4%) The storm along the northeast U.S. coast had predictions of plenty of precipitation, but it was not a snow storm for New York City.  Why not? 

 

c. ( 4%) Cooperstown, ND (yes, there is such a place) is marked as a red dot with the designation COO on the 48 hour forecast precipitation map. Cooperstown will receive snow from the storm in the northern Great Plains. What is the NAM forecast for liquid equivalent precipitation and actual snowfall expected in the 48 hours after initialization?  Give two numbers with appropriate units.

 

 

2. On January 27, 2015, a snowstorm was predicted for New York City.  In fact, the city was under a blizzard warning and predicted snowfall amounts were 20-30 inches.  Central Park reported 9.8 inches, a heavy snowfall but not close to 30 inches.

        We know the situation by looking at the 12Z U.S. surface analysis map, the North American NAM MSLP initialization, 500 mb vorticity map, and the 300 mb map.  These are not forecasts.  The dire forecasts were issued two days earlier from the 48 hour NAM forecasts for MSLP/1000-500 mb thickness, 500 mb vorticity, and 300 mb. 

            a. ( 6%) On the paper NAM 300 mb forecast for New York City Central Park, mark the following:  The Polar Jet Stream that is causing the trough to deepen (mark it “Polar Jet”, heights that have created a ridge by backing (mark it “ridge”), Negative Tilt (draw the axis as a thick dashed line).

b. ( 5%) What happened that can be seen on the 12Z Jan 27 verification weather maps that was different from the 48 hour forecasts for 12Z Jan 27?  In other words, what happened that was incorrectly forecast that would have accounted for the drastically lower snowfall totals in NYC?  Hint:  these were excellent, but not perfect forecasts.  Look closely for small differences and use those to explain why NYC got 9.8” instead of 30” of snow.

 

 

3. This is a severe thunderstorm forecast question. For an undated situation, you are given individual maps of 00Z NAM forecasts.  Assume the forecasts are perfectly correct and that severe weather was very strongly occurring at 00Z.  You have forecasts (all 00Z) of the MSLP/thickness, MSLP/2 m temperature, 850 mb height/temperature, 850 mb height/RH, 700 mb height/RH/Omega, 500 mb height/abs vorticity, and 300 mb height/wind.

           

            a. ( 18%) On one blank U.S. map supplied, create a 00Z composite chart using the methodology of Col. R.C. Miller.  Your map must have a key to all symbols used.

            b. ( 5%) On the second blank U.S. map, draw a day 1 convective outlook, using the standard SPC format.   It is not necessary to put in the color fill, but use colored lines to show all necessary symbols and labels, again in the SPC format.

            c. ( 10%) Write a discussion of the meteorological situation at 00Z, based on the maps you were given.  Your discussion is not for the general public.  Write it for professional meteorologists to read.  Provide the relevant information for severe thunderstorms and draw conclusions.

 

4. Three storms are chosen out of the multitude that affected the U.S. this past winter.  PowerPoint loops are provided for December 30 (surface, 500 mb, 250 mb), Jan 18 (surface, 500 mb, 250 mb),  and Feb 13 (surface, 500 mb, 250 mb). The first surface map in each loop has one city marked directly south of the station:  December 30: KLWT (Lewistown, MT), Jan 18: KMKC (Kansas City, MO), and Feb 13: KALB (Albany, NY).  You will see that the surface maps for KALB are only for the Northeast U.S.  Also, each set of maps shows a single 24-hour period..

 

            a. ( 9%) For each of the three dates, what type of storm is affecting the marked city for that date?  Use the upper air maps to assist you, if necessary.

 

            b. (12%) For each of the three cities, summarize the precipitation types and temperatures that occur in each 24-hour period. Do not just list the observations every 3 hours but you must report the changes.

 

 

5. The ASOS reports from the region centered on Alabama at 1423 UTC on 15 April 2019 are presented on a map. Somewhere on this map there is an observation that is very questionable.. 

a. ( 3%) Identify the 3-letter code of the station showing the questionable observation (codes are, as always, to the lower right of the station circles) and specify its geographical location (i.e., northern Georgia, eastern Tennessee, etc.). 

b. ( 6%) What is the meteorological observation that is not believable and why don’t you believe it? 

 

6. For this question, use the following maps, each of which consists of a 48 hour forecast and the verification.  You have one set from the NAM and one from the GFS.  Each forecast was initialized at 18Z and verified exactly 48 hours later. Each forecast shows precipitation maxima in the Gulf of Mexico and over the southern Gulf States.

 

a. ( 4%) The NAM 48 hour forecast precipitation was quite different from that of the GFS but both models made a fundamental error in placing a Low which explains the precipitation errors over Gulf coast states Texas, Arkansas, Louisiana, and Mississippi.  What is that error in the forecast position of the Low in the Gulf?  Note, this is a short answer (one sentence).

           

b. ( 8%) Considering the error of the Low pressure in the Gulf from part a, explain how the error leads to a the forecast wind pattern around that Low that in a convective parameterization scheme works to produce GFS precipitation maxima at least twice that of the verification?