Friday, January 15, 2010

Severe Threat Next Wednesday Looks Weaker

What a difference a day makes. This time yesterday the "red flag" was flown as forecast models were hinting at a potential tornado outbreak nest Wednesday. Since yesterday morning, forecast models have trended away from a major severe weather event. We are still looking at the possibility of strong storms with small hail but the overall severe threat looks pretty minimal. Below is the new forecast sounding for Wednesday. The timing has moved forward about 6 hours and the amount of CAPE has been nearly cut in half (see yesterday's forecast sounding for Wed). This indicates that the storms' updrafts would be much weaker than what was forecast earlier. So the threat of large hail has diminished greatly. In addition you will notice that the wind speeds through the CAPE have weakened nearly 50 knots making the threat for severe winds gusts much less as well. .

Finally for the tornado threat. The 0-1km SRH helicity is much less than indicated by yesterday's hodograph

Notice the low level turning of wind with height is very small, no greater than we would find on a typical summer afternoon thunderstorm event. So the tornado threat has gone from very large to almost zero. Now again, we are still a long way out from this event and this storm system could become much stronger than currently forecast. My forecasting experience tells me this system is probably being advertised too weak and a blend of yesterday's model run with today's would probably produce the best forecast. This would lead to a few strong to severe storms and maybe an isolated tornado but, the tornado outbreak I was thinking could happen yesterday, more than likely will not occur.

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