METR 361 Final Exam

METR 361 Spring, 2017

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). Answer all parts of all six questions in the blue books except where you are directed to draw on the paper copies. If you like, you may instead send me your electronic answers in a text, Word, or Open Office Writer (.odt) file. You have 2 1/2 hours.

1. (5%) Starting with an ASOS question, refer to the surface observations for 18Z April 19, 2015. Almost all the stations in Pennsylvania and the southern tier of New York State are reporting something incorrectly as shown in the loop of visible satellite images. What is the error and why does it routinely happen?

2. Here’s a situation that occurred during an unspecified range of dates sometime in the current academic year. You have PowerPoint loops of the GFS forecasts from 120 hours to 180 hours for 250 mb, 500 mb, 850 mb, and two types of MSLP forecasts, one with 2-meter temperature and one with thickness.

a. ( 3%) During the 2 ½ day forecast period, an extratropical cyclone occurs in the U.S. (yes, only one). What is the name for this type of storm?

b. ( 9%) Three cities are marked on a blank U.S. basemap, Denver Colorado (KDEN), Dallas, Texas (KDFW), and Binghamton, New York (KBGM). List the precipitation type which is consistent with the situation shown during the forecast period at each of these cities? You must give 3 short answers.

3. This question requires you to identify severe weather ingredients on standard maps. You have two paper copies of each of the maps, one for rough sketches and one to turn in. Make that one neat and finished.

a. ( 27%) For the surface map, find two possible lifting mechanisms for severe weather. Draw those on the second (good) surface map, using the proper symbols and identify what you chose in the blue book or text file.

For 850 hPa, find all three favorable “ingredients” for severe thunderstorms. Label their map location(s).

For 700 hPa, 500 hPa, 300 hPa, and 200 hPa, find one favorable ingredient on each map. Label their map locations.

In crafting your answers to this part, you may draw on the rough copies to better visualize the atmospheric fields but do not turn those rough copies in. On the second (good) copies of the MSLP, 850 hPa, 700 hPa,, 500 hPa, 300 hPa, and 200 hPa maps, you must mark neatly the areas where your ingredients were most favorable for severe thunderstorms with the names of these features. Write large enough so I can see the feature locations clearly and unambiguously. Turn in only the good copies.

b. ( 5%) On the blank U.S. map provided for question 2, draw a convective outlook using the standard format and nomenclature used by the SPC for a Day 1 outlook. Your convective outlook must fit the conditions shown in your five maps for part a and is only valid for 00Z on the date of those maps (blanked out of the maps). You must identify the area at risk for severe thunderstorms but omit the area of general thunderstorms.

c. ( 5%) Write a short weather discussion, suitable for a professional meteorologist who wants to know the situation quickly, informing him/her of the likelihood of severe thunderstorms at 00Z on the date of the maps. You should not calculate any probabilities but use the standard nomenclature for convective outlooks in your discussion .

4. This question is about a 12Z sounding from Dallas-Fort Worth, TX.

a. ( 9%) Name three aspects of this sounding that are favorable for severe thunderstorms. You should not explain them, just name them.

b. ( 3%) Assume the afternoon maximum temperature reaches 30°C (86°F) with no change in the surface dew point from the 12Z value. What is the LFC of surface air which is lifted at the time of max temperature?

c. ( 12%) Assume the same conditions as in part b. What severe weather types are supported by this sounding? Briefly explain your reasoning.

5. Compare the 00Z July 2, 2016 surface map with the U.S. Radar composite map. Also, you have a 300 mb map, a 200 mb map, and a 500 mb vorticity map.

( 8%) Clearly the radar echoes in the northeast U.S. and in eastern Colorado/western Nebraska are associated with the frontal system seen on the surface map. But the widespread echoes in the mountain west (western Colorado and Wyoming, Utah, Nevada, Arizona, and New Mexico) are in the same place as a large area of high pressure. Explain meteorologically the precipitation shown on the maps in the mountain west states only. Be sure to refer to the time of year and any other factors which lead to the precipitation echoes as shown. You may use any of the maps given.

6. 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 20 inches.

We know the situation by looking at the U.S. surface maps for 06Z and 12Z. We also have the 06Z North American surface, and the 12Z 850 mb, 500 mb heights, 500 mb vorticity, 300 mb, and 200 mb maps.

The dire forecasts were issued two days earlier and the 42 hour NAM forecasts for MSLP/1000-500 mb thickness, 850 mb, 500 mb, 300 mb, 200 mb and the NYC sounding are also available. The forecast maps are for 06Z, not 12Z, but the reasoning behind this snowfall total error will not change because the maps are at a different time.

a. ( 4%) On the paper NAM 300 mb forecast for New York City Central Park, mark the following: Any Polar Jet Stream, Any Subtropical Jet Stream, Backing Heights, Negative Tilt.

b. ( 10%) What happened that can be seen on the verification weather maps that was different from the 42 hour forecasts? To answer this, suggest a plausible scenario involving changes to the forecast 06Z January 27, 2015 maps that would have accounted for the drastically lower snowfall totals in NYC, consistent with the verification maps. In other words, you must propose different locations for the forecast weather elements. Also, for your scenario, explain why the differences you propose to the forecast maps would have been consistent with a 10 inch snowfall, rather than a 30 inch snowfall in New York City.