Tragedy in MO and Oddity in FL

4/28/2012 severe weather, strange No Comments

Two big weather stories are making news this afternoon -- the first of which is tragic, the second of which is downright bizarre.

KSDK-TV St. Louis

As I wrote earlier this morning, a series of strong storms has impacted the St. Louis area eastward through the Ohio River Valley, bringing huge hail (up to 3" in diameter) and strong winds in excess of 70 MPH. According to news reports, over 100 people were underneath or near a tent at a St. Louis sports bar when severe thunderstorm winds destroyed the tent. KSDK reports over 100 injuries and 1 confirmed fatality so far from the disaster. This event is eerily reminiscent of the Sugarland concert last year wherein strong thunderstorm winds collapsed the stage, killing 5 and injuring many more.

A few hundred miles to the southeast, we run into our bizarre story near Tallahassee, FL. Twice a day (at 00z and 12z), weather observing stations across the globe release weather balloons with radiosondes (weather instrument packages) attached to the balloon by a string. As the balloon ascends through the atmosphere, it expands until it eventually pops. Once it pops, a parachute in the radiosonde package opens and gently allows the instruments to descend to earth. Within the package is a postage-paid mailing bag so anyone who finds it can mail the package back to the NWS so it can be reused.

Image from NWS Tallahassee showing the approximate path of this morning's weather balloon.

Well...they usually land in open fields, rooftops, or in the water, but the one released this morning in Tallahassee, FL landed on a person. According to the NWS office in Tallahassee, given the population density of the area in which the balloon landed, the odds of that happening are 1 in 506,800,000,000,000,000. That's a 1 in almost 507 quadrillion chance.

As one of the commenters on the Facebook post said, that person should go get a lottery ticket ASAP.

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National Forecast: Saturday April 28 2012

4/28/2012 forecast No Comments

Unsettled weather will occur over much of the country on Saturday, with parts of the northern Rockies experiencing snow, and a large swath of thunderstorm activity expected from Kansas towards the Atlantic seaboard developing during the afternoon.

SPC's severe weather outlook, issued at 1130AM CDT. 

A relatively weak surface low will move eastward across northern Missouri during the day on Saturday, off of which a warm front will extend from central Missouri eastward across the Ohio River. This warm front will serve as the focus for some severe thunderstorms in the area as daytime heating takes over and instability has a chance to take hold. The Storm Prediction Center has issued a slight risk for severe weather from around St. Louis MO eastward through eastern Kentucky. The models are showing bulk shear across the risk region varying between 40 and 60 knots, which will mean that the convection will be in the form of supercells, lines, or both. The most likely scenario is that the initial form of convection will be supercells (which then congeals into a line), or a line of storms forms with embedded supercells within.

The 00z NAM shows that the environment in the area is forecast to be able to support hail up to around 2.00" in diameter, which is slightly larger than golf ball size. Given that helicity (a measure of the amount of rotation a storm could tap into) is pretty low, the tornado threat across the Ohio River Valley won't be too terribly high, but not non-existent. The main threats will be in the form of large hail and damaging winds (the former during supercells, the latter when the storms turn linear).

Another slightly greater threat for severe weather exists over the southern plains, including Oklahoma City and points southwestward through Abilene, TX. The SPC says that the threat will come in two rounds:

Round 1 will occur late in the afternoon with the development of supercells in the threat area. Large hail and damaging winds will be the primary threat, with tornadoes a possibility "depend[ing] strongly on the status of convective mode by about 00z-01z," meaning that if the storms aren't supercellular by 7 or 8 PM CDT, the threat for tornadoes will drop off dramatically.

Round 2 will occur early Sunday morning, with elevated convection further to the west over the TX Panhandle and parts of OK, KS, and NM. The SPC says that this convection will mainly bring "significant" hail of golf ball size or larger.

Aside from the severe weather threat, a decent little snowstorm will affect the northern Rockies during the day on Saturday, lasting into Sunday in some places. Amounts of about 4-10 inches can be expected at the higher elevations, with more or less depending heavily on terrain and location. Below is the HPC's probability of at least 4" of snow occurring at any one point within the contour.

Aside from those three areas, everything looks to be fairly innocuous for late April. Enjoy your Saturday!

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