Severe Risk Thursday

Severe storms are possible in the Commonwealth Thursday afternoon, capable of producing locally damaging winds, large hail, and even isolated tornadoes.

We remain in an upper-level northwest flow pattern, where upper-level disturbances continue to pulse through the region. At the surface, a low pressure system will track just to our north today. These factors will provide the lift necessary for storms, but we will also have the afternoon heating today that we did not have on Wednesday. Breaks in the clouds should occur by mid-day, allowing afternoon temperatures to rise into the mid-80's, a good ten degrees warmer than our highs on Wednesday.

Initially, storms should form in the higher terrain of Western Virginia, then track eastward into Central Virginia this afternoon. There is at least a chance for an isolated tornado, as conditions appear conducive for supporting rotating storms.

Chief Meteorologist Zach Daniel will be monitoring the threat this afternoon!

There were several tornadoes yesterday in the Plains, but here is great video of one from Aurora, Nebraska:


For a full list of the severe weather reports Wednesday in the country, click here.
--Carrie

Severe Weather Possible Thursday

Conditions Thursday afternoon should come together to produce scattered severe thunderstorms in central Virginia. The strongest storms will contain large hail and damaging wind gusts. There will also be a threat for a few tornadoes along a trough line that should be located roughly parallel to the Blue Ridge, and also in the vicinity of a surface low in north-central Virginia. Check back early Thursday for the latest on what to expect.

El Niño Watch

The surface water of the Equatorial Pacific is showing signs of becoming warmer than average, which would indicate a transition to El Niño conditions. That region has remained "neutral" through May, but temperatures have been gradually rising for five months. By the end of May, sea surface temperatures were about +0.4° to +0.5°C in the critical region, which suggest the beginning of an El Niño. Read the entire ENSO Discussion.

Based on these recent trends, it is likely that the Equatorial Pacific will transition to El Niño conditions from June through August 2009. Read the latest weekly update here.

Our most recent ENSO episode was a La Niña from August 2007 to June of 2008. Since then, we have been in weak La Niña transitioning to neutral conditions through 2009 so far.

The last El Niño episode was July 2006 through February 2007.

What could El Niño mean for the Commonwealth? Well, not much. For a Summertime El Niño episode, not much deviation from average is documented for Virginia. In fact in the United States, only the Rocky Mountain West shows any substantial response in the Summer to an El Niño with wetter than average conditions. The U.S. tends to experience more noticeable climate impacts during a Winter El Niño event.

(Click to enlarge this graphic)

Well, what about impacts from El Niño on the Atlantic Hurricane Season? Research has shown that El Niño's wind profiles encourage the development of more eastern Pacific hurricanes, while hindering the development of Atlantic hurricanes. La Niña leads to the opposite, with fewer eastern Pacific hurricanes and more Atlantic hurricanes. Read here for a full discussion on ENSO's possible impact on tropical activity. So this means that the chances for the Atlantic and Gulf Coasts to receive a hurricane are reduced. However, this does not mean that hurricanes cannot form and do significant damage during an El Niño season.

--Carrie