Thursday, December 24, 2009

Moderate Risk on the Eve

Well I have talked about this for several days now and here we go for a severe day of storms on Christmas Eve.

**Storm Prediction Center in Norman, OK, will upgrade the risk to a Moderate Risk for SE LA and South MS at 10:35am.** This means our atmosphere will continue to be favorable for tornadic supercells forming in advance of the propagating cold front.

A deep 997mb surface Low is present in Eastern TX, which is slightly farther south than expected. This is also why we believe our risk should increase as well. Multiple tornadoes have already been tracked in Louisiana as the line nears the Mississippi River late in the morning. I'm expecting the line to speed up as it crosses into MS with help from the dry cold front propelling it forward. We could also see strong gradient wind out ahead of the cold front. This will not be storm related wind but only pressure gradient wind from the strong gradient induced setup. We could see gust between 25-40mph ahead of the cold front.

Early afternoon, the updraft into any supercell will easily contain a rotating component with the strong storm relative helicity values present. Thermodynamics (instability) is still lacking, but the strong system dynamics have already produced tornadoes this morning. Also along the squall line damaging winds of 55+mph are a concern. So we will be on high alert this afternoon for eyeballing strong supercells approaching our viewing area.

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