VORTEX STATUS MESSAGE AND FORECAST DISCUSSION NATIONAL SEVERE STORMS LABORATORY 1130 AM CDT APRIL 19 1995 OPERATIONAL STATUS AT 1130 CDT: GO TARGET AREA: NORTH TX SUPPLEMENTAL SOUNDING/ARCHIVE II REQUESTS: SELS has reques- ted 18Z soundings at AMA,OUN,FWD,SHV,MAF,DRT,CRP. VORTEX requested 21Z soundings at all the sites in the VORTEX ops area. Level II archives at FWD, LBB, DYS, KFDR are likely to be very important. DAILY FORECAST DISCUSSION: Interesting situation, with a lot of positives and some neg- atives. Positives include increasing instability, with 700- 500 mb delta-ts having increased markedly overnight, as H500 cooling and H700 warming has occurred in advance of the sig- nificant short wave trough over southern AZ at 12Z. Progs show a mixed bag of expectations. Looks like a compromise among them will have the vort max entering west TX at about 00Z and a surface low somewhere near ABI, with a strong dry push developing south from the surface low. Very strong winds through most of the troposphere and backed low- level winds even south of the surface boundary in north TX bode well for helicities today. With increasing moisture in south easterly flow in southeast TX, expect significant CAPE values as upward motion continues development of hi lapse rates, perhaps as high as 2500-3000 j kg-1. Helicities in the 400-600 j kg-1 range are also possible. Some problems: in order to put good storms in the VORTEX ops area, the surface boundary has to give way and retreat some towards the Red River. The pesky northeasterly winds and cool temperatures in central TX seem to be relenting by 16Z, so this may be all right. Another issue is the cap. In order to keep the warm moist air at low levels moving northward, convection should be suppressed as long as pos- sible ... it appears so far to be held in check. The cap then needs to be broken, preferably in the vicinity of the dryline, to get good storms up. It appears with the vigor- ous trough approaching that the latter will happen. Thus, expect storms to develop somewhere near ABI and south- ward from there and move rapidly northeastward. With the strong flow through most of the troposphere, the storms will` be moving smartly, and only modest right turns are expected, on the order of 20 deg. If everything works out right, this could be a major tornadic event in north TX. Have not looked at tomorrow very much, but it appears from the progs that things will be pretty much suppressed as the major wave continues to lift out pretty much as the last one did, toward the Great Lakes with severe thunderstorms into the Ohio Valley, as well. Doswell/Janish PROBABILITIES OF OCCURRENCE IN VORTEX OPS AREA THRU 04Z (DAY1) AND 12-04Z (DAY2)... DAY1 DAY2 LIGHTNING 90 10 SEVERE 80 05 TORNADOES 70 02 TARGETABLE STORM 80 02 FCST STORM MOTION - TARGETABLE STORMS ONLY PRE-SUPERCELL 250/40 -N/A- SUPERCELL 270/30 -N/A- FCST INITIATION TIMES (LT) - TARGETABLE STORMS ONLY LIGHTNING 1530 -N/A- 1ST SEVERE RPT 1630 -N/A- 1ST TORNADO 1700 -N/A-