Tuesday, January 29, 2013

Severe Weather Event Getting Underway...

As expected, thunderstorms formed during the pre-dawn hours from western Oklahoma into southeast Kansas and west-central Missouri.  The activity is racing toward the North/Northeast, while gradually shifting Eastward over time:

There have been isolated reports of hail and/or wind gusts near severe limits thus far in west-central Oklahoma, but nothing widespread or major through the time of this writing.

The development thus far has taken place ahead of a strong middle and upper level weather disturbance that is currently centered over the southern Rockies:

This disturbance will lift out to the Northeast during the day today, resulting in an increasing threat of severe weather (with respect to both coverage and intensity) across the southern and central Plains, Deep South and Mississippi Valley regions.

The latest severe weather outlook from the Storm Prediction Center is shown below, valid for today and tonight:

This particular graphic is focused on the wind damage threat, which I continue to believe will be the primary severe weather mode today and tonight.  The red and lavender shaded and black hatched areas are where intense, very damaging winds are possible over a fairly widespread area.  The jet stream will be blowing overhead of this region at speeds well in excess of 100 mph later today and tonight, and some of those intense winds are likely to "mix down" to the surface in association with some of the most severe storms.

While wind damage will be the primary severe weather mode today and tonight, there is still a risk of tornado development in two primary ways:

(1).  In association with any isolated storms that are able to form out ahead of the developing line or lines of storms

(2).  In association with any rotating "comma heads" or "dog legs" that form along the lines of storms

I took a screen shot of a "dog leg" on a small line in Oklahoma earlier this morning (circled in white on the following image):

The trick with the linear severe storm tornado situations is that the tornadoes tend to be very brief, making radar detection difficult.  As in the example above, on the next radar scan about 4 minutes later, the "dog leg" rotational signature was gone.

The best chance of tornado spin-ups today will be within the red and lavender shaded areas on the outlook image above.  Keep in mind that part of this risk (the Eastern portions of the risk area) will take place after dark and into tonight.

If any isolated storms are able to form ahead of the main line or lines, they could potentially produce a stronger or longer track tornado, but I do not expect this to be a general rule today.  Therefore, I believe using the term "tornado outbreak" does not apply to the situation today.  A severe weather outbreak is certainly possible, with wind damage being the primary feature.

Hail up to around 1 inch in diameter is also possible with the stronger storms.  A more vigorous storm or two could produce locally larger hail, but the overall scenario does not favor widespread large hail production today.

If you live in or near the severe weather threat areas for today and tonight, please remain alert.  Make sure that you have a way to receive severe weather warnings, including overnight tonight in the Deep South and Mississippi Valley region.

Please review your severe weather safety and sheltering tips this morning, that way you're ready to seek shelter at a moments notice later today if threatening weather approaches your area.

The best way to receive "live" updates from me today will be to follow on the twitter and/or facebook links below.  Radar and watch links will also be updated here on the blog homepage throughout the day, along the right hand side of the page.

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