TAMDAR Discussion Board

Good low level moisture support

Posted By: Lyle Alexander
Date: 12-November-05 1728Z

With a strong low pressure system in central Nebraska, we are witnessing another in a series of November warm surges in the Mississippi Valley and TAMDAR showed that the moisture was spreading northward earlier than expected. A sounding from an ascending aircraft from MLI (Moline, IL) at 1234Z showed a dew point of 13.3C at 900 mb. The operational RUC had a dew point of around 10C for 12Z at that location but then lowered the values for late morning. The TAMDAR dev2 kept higher dew points at 850 and 900 mb through the morning, aided by several soundings in IL at around 12 and 13Z. When new soundings arrived at around 16Z, I evaluated the highest dew points in the 850 to 900 millibar level: CMI Sounding 12.6 901mb ........oper RUC 4.9 864mb TAMDAR dev2 7.7 892mb MLI Sounding 13.7 901mb ........oper RUC 5.6 901mb TAMDAR dev2 10.7 873mb The moisture surge produced a cluster of lightning strikes about 45 miles west of STL at 1450Z with coop reports of showers in that area. Area radars showed widespread echo tops of 25 to 30 thousand feet in a band from the southwest corner of Wisconsin, through the Quincy IL area to northern Arkansas. The showalter index where the lightning strikes off the NWS RUC was +2 but it was probably negative. The 12Z Mesoeta did a better job with the low level moisture (still lacking however) with a showalter of -1 for the time and location of the lightning. Along the band of moisture being discussed, 16Z temperatures were around 60 with dew points around 40 so rain reaching the ground was relatively scarce. A more significant band of low level moisture was situated a couple of hundred miles to the west. Lyle Alexander