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Virtual Severe Weather Forecast and Chase Contest

tornadotony

By tornadotony,
in Central/Western States

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tornadotony

tornadotony

Posted
Posted

I thought it would be fun to create a virtual chase of sorts while we're waiting for the actual chase season to really heat up. Here's how will do this:

1) Posted will be a 12z, 15z, and 18z sfc chart, and 12z 850hPa, 700hPa, 500hPa, and 300hPa upper-air chart, unanalyzed (raw station models) for the date in question (you will not be able to see the date).

2) Your goal is to create an SPC-style categorical outlook (no thunder, general thunderstorms, see text, slight risk, moderate risk, high risk) for that day. Note: the chosen date may or may not actually be a severe weather event! You can use maps, text, or both to create the outlook. Be creative!

3) Pick a target city that you would choose for a chase that day, if you decide to chase. For null cases, let us know if you're sitting back at home floating around the swimming pool (or going fishing or hunting, something besides chasing).

Scoring will go as follows:

- Up to 5 points for the correct maximum outlook category. For this, I will use the general rules of thumb (all values for an area approx. 50,000 sq. mi., or Oklahoma minus the panhandle):

--> No thunder: well, no thunderstorms at all, duh

--> General thunderstorms: no severe reports this day, but there was at least one thunderstorm observed

--> See text: 0-10 hail/wind reports, up to 2 tornado reports

--> Slight risk: 10-40 hail/wind reports, 2-6 tornado reports

--> Moderate risk: 40-70 hail/wind reports, 6-19 tornado reports

--> High risk: 70 or more wind reports, with 5 or more 65kt or greater; 20 or more tornadoes, with 2 or more rated F3/EF3 or higher; HAIL CANNOT VERIFY A HIGH RISK

- Up to 2 points for being within one category of the right category for the outlook

Note: I will subjectively factor in placement of risk areas. I will lean generous, but you need to be in the ballparks, especially for moderate and high risk areas.

- For the chase city:

Tornadoes:

-->5 points if an EF0-EF2 tornado strikes the county in which your city is located

-->10 points if an EF3-EF4 tornado strikes the county in which your city is located

-->25 points if an EF5 tornado strikes the county in which your city is located

-->2 points if an EF0-EF2 tornado strikes a county that neighbors OR corners the county in which your city is located

-->4 points if an EF3-EF4 tornado strikes a county that neighbors OR corners the county in which your city is located

-->10 points if an EF5 tornado strikes a county that neighbors OR corners the county in which your city is located

Hail/wind:

-->2 points if hail 1"-1.75" or wind 58-74 MPH occurs in the county in which your city is located

-->4 points if hail 2"-4.50" or wind 75-99 MPH occurs in the county in which your city is located

-->6 points if hail >4.50" or wind 100MPH+ occurs in the county in which your city is located

-->1/2 the number of points listed above for events in neighboring/cornering counties

WILD CARD: I will be secretly ranking the difficulty of each case from 1-3, with one being the easiest, 3 being the hardest. For any cases rated 3, the points double.

I will post the first case shortly.

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Thundersnow12

Thundersnow12

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Posted

few things I'm noticing..

1. The warm front is advancing northward nicely throughout the morning into the early afternoon sitting at about the IA/MO border at 18z extending eastward to I-80 in northern IL. Also have strong sfc low in the warm sector as well as strong easterly flow north of the warm front

2. It looks like a there is a confluent zone/wind shift ahead of the dryline which you can see on the 12z and 15z sfc maps.

3. A strong EML with an area of very steep H5-H7 lapse rates of greater than 20 degrees from OK northward to NE and H7 temps quite warm in the southern plains.

4. A really strong sfc low that continues to deepen throughout the day sitting at 986mb in central NE at 18z.

5. big time diffluent area in southern NE at H5.

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tornadotony

tornadotony

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any chance we could get a 19z or 20z sfc map? or a few vis sat images?

That would take the fun out of it. :) I'm modeling this after an assignment I had in my Severe Storm Prediction and Nowcasting class that I took last year. You've got exactly what I had to work with. Only I had 30min. :unsure:

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tornadotony

tornadotony

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In terms of satellite, my big hint (that especially is for this case) is to use the station plot and the surface conditions to try to infer the type of clouds that are in place, and then use the upper-air data to try to predict how cloudcover will develop during the course of the afternoon.

As for a later sfc map, what fun is forecasting if you know the obs during the (potential) event? ;)

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Thundersnow12

Thundersnow12

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That would take the fun out of it. :) I'm modeling this after an assignment I had in my Severe Storm Prediction and Nowcasting class that I took last year. You've got exactly what I had to work with. Only I had 30min. :unsure:

alright alright lol have my area but will make the map and stuff tomorrow during the day.

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Chinook

Chinook

Posted
Posted

This is a late April or early May day with a strong cool/dry push in Kansas and a strong fast-moving shortwave trough moving from Denver through Nebraska during the daytime. There are 90kt winds at Vance AFB OK at 500mb, and this will provide strong wind shear to fuel up some strong supercells in Missouri, Illinois, and Arkansas, and parts of KY and TN. At 18z, the unstable areas are south of Springfield IL and south of Des Moines. It is very unstable near the southern tip of Illinois. I put the 15%, 30%, and 45% as the SPC does, meaning slight risk/moderate risk. Storms will be fast-moving, and there is going to be a quick evolution from supercells to linear MCSs.

My chase pick is Marion, IL.

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thewxmann

thewxmann

Posted
Posted

First off, thanks for setting this up Tony. I love these games.

I typically suck at these, but some general observations....

1) This is a very progressive system. The dryline marches from ctrl KS/wrn OK to the eastern portions of those states within a span of six hours.

2) This *feels* like an early season negative-tilt bowling ball setup (Mar-Apr). 80 kt at 500mb is nothing to sneeze at. Note the 180 degree turning of H5 winds between DEN and LBF, and the SE winds at H3 at KRAP (significant negative tilt).

3) The SW'ly winds at 850 are significant, and suggest to me that the DL will continue to surge eastward. Not surprisingly, surface winds have veered significantly between 12Z and 18Z south of I-70. Accordingly, moisture at 850mb has just about mixed out in all locations (& sfc Td's are decreasing per SGF obs). I would give areas south of I-70 a SLGT risk at best. Any storms that do form in this region will likely be linear or otherwise disorganized and nondiscrete. The southern edge of this SLGT will be dictated by a rough 700mb cap estimation; assuming a Mar-Apr setup, anything above 9C is off-limits for deep, sfc-based initiation. I will be generous (as SPC usu is) and put the southern edge of the SLGT around I-20 in NE Texas.

4) As is usual with bowling ball setups, the best shot may be near the cold core. At 18Z the sfc low/triple pt is around SE NE, juxtaposed with good diffluence in the upper levels. Lapse rates are nice and steep. In addition, the leading edge of the dry punch (850mb Td of 2C at TOP at 18Z, and H7 jet streak approaching indicated area) is nosing in. Winds are backed north of the warm front... cloudcover is defin a concern but with the dry punch coming in we could see some clearing real soon. I wouldn't be surprised to see initiation in just a couple of hours, cold-core style, NW MO to SW IA. Areas here and just east would be a good area for tornadic activity, and as such, this is where my MDT risk would be.

I will draw a map later. I target would be somewhere near Bedford, IA or maybe just a little bit east.

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tornadotony

tornadotony

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Final specification (as I'm going through and giving scores to current entries); though you can get points for many counties, you can only get one type of point for each county. Thus, if you have 10 tornadoes in your county, you will get scored only for the strongest single one. You will not get 10 different sets of points. But you can score 10 times if you get a tornado in your county and in nine neighboring/cornering counties.

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Thundersnow12

Thundersnow12

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a few questions remain on exactly how far north the warm front continues to move after 18z as well as the amount of clearing going on but with the nice moisture axis up through northwest MO to the OAX area and moving east coupled with alot of shear to work with, I would think we could have a few tornadic supercells go up on the dryline and possibly ride the warm front.

We all can see the dryline is hauling east with the sfc winds in western MO already starting to veer around to the south between 15-18z so I would expect the dryline to sweep into MO within the next few hours

storms will be moving quickly given the strong mid-level winds (50-70kt H7 jet streak coming in) so I will stay a bit further east and let storms develop.

Target city: Centerville, IA

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