Drones To Study Hurricanes

NASA will begin flying drones into hurricanes in order to study their structure and the environment in which they form.

How To Track Severe Weather: The SPC

A primer on how to use the Storm Prediction Center's website to keep track of severe weather.

What is a derecho?

A post explaining the dangerous (and common) type of convection called a "derecho."

Remembering April 27, 2011

A discussion about the worst tornado outbreak in recorded American history.

Explaining Heat Bursts

Explaining the relatively uncommon phenomenon known as "heat bursts."

Sunday, May 20, 2012

2012 Severe Weather Season Below Average So Far

After the constant tornado outbreaks of 2011, any severe weather season is going to seem pretty relaxed in comparison. However, save for the major tornado outbreak on March 2, 2012, the 2012 severe weather season has been pretty lacking.

Severe weather reports come in 3 categories -- tornado reports, large hail reports, and damaging wind reports. Tornado reports include both tornadoes and funnel clouds. Large hail is tricky: up until 2010, large hail was classified as 3/4" diameter or larger, and ever since they've been classified as hail 1.00" or larger. Damaging wind reports include any thunderstorm winds measure at 58 MPH or greater, or any thunderstorm winds that cause damage, regardless of speed.

Over the last 10 years, we've seen an average of 27184 severe weather reports per year, including 1387 tornado reports, 9417 large hail reports, and 13,338 damaging wind reports.

As we're only about halfway through the year, it wouldn't be fair to compare the 5 month 2012 severe weather season to an entire year's worth of tornadoes, hail, and wind. Through some Excel trickery, I've isolated the averages to include only January-May.

The average number of severe weather reports through the month of May turns out to about 10475. So far, we've only had 6,489 reports of severe weather.




The average number of tornado reports through the month of May is 687, which comes out to almost exactly what we've seen in 2012: 689.




The average number of hail reports over the same time period is 5971, and even though extremely large hail is constantly in the news recently, we've only had 3218 severe hail reports so far this year.




The average number of damaging wind reports over the last 5 months comes out to be 3873, and we've only had 2,582 severe weather reports up until now.




As noted at the beginning of the diary, most of this year's severe weather came in a few outbreaks which were able to bump the yearly average up to just slightly below average. The uptick in severe weather in January came in an early season severe weather outbreak across parts of the southern United States. The large spike in tornado/hail reports came in the devastating high-risk tornado outbreak on March 2nd across parts of Tennessee, Kentucky, Indiana, and Ohio.

Aside from that, even though we've had some pretty good severe weather events, the results weren't enough to bump us up to or over the averages for this period of the year so far.

If you like severe weather, the year is far from over. We usually see an uptick in damaging wind reports (which tend to be more numerous than hail or tornado reports) during the middle of the summer when intense mesoscale convective systems and derechos get going -- essentially, powerful lines of storms that tend to have very strong damaging winds.

For those of us going on severe weather fatigue, this is good news. Let's hope the below-average trend continues.

TS Alberto: Rainbands Impacting GA, Turn To Northeast Imminent

As of the 11AM EDT advisory from the National Hurricane Center, Tropical Storm Alberto was still drifting along towards the southwest with 45 MPH winds. A Tropical Storm Watch is still in effect for parts of the South Carolina coast, but the odds of these areas experiencing tropical storm conditions are lowering with each tick of the storm away from SC.



As seen above, Alberto is a photogenic storm on satellite due to the lack of convection around the center of the system. All of the storm activity within Alberto is located on the western side of the storm, with rainbands (with less than tropical storm force winds) impacting coastal counties of Georgia at this time. The NHC expects Alberto to just barely hang in there as a Tropical Storm over the next couple of days, before turning extra-tropical and dissipating towards the middle of the week.

Alberto is currently moving towards the southwest, but an approaching midlevel trough will force the storm to turn right back around and start moving northeast. A low pressure system is currently sitting about 50 miles east of Ocean City, MD right now, which is effectively serving to block Tropical Storm Alberto from racing northeastward out to sea. This low is forecast to move inland over the next few days, which will open up a large ridge over the Atlantic and allow Alberto to move progressively faster out to sea.

12z NAM 51 hour 500 millibar height/wind/vorticity forecast.
As the storm moves northeast on Tuesday, the center of the storm will come fairly close to the Outer Banks of North Carolina. Provided the storm is able to hold itself together, there's a real possibility of these areas going under a Tropical Storm Watch or Warning by tomorrow evening as the storm approaches. It won't be a memorable storm by any means in terms of damage, surge, or flooding, but still worthy of attention if you live along the Carolina coast.

Wunderground Forecast

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Active Watches & Warnings

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Blue = Severe T'storm Watch

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