Here we go again: severe weather outbreak possible Nov 27/28
Posted: Wed Nov 23, 2005 7:31 pm
All right, I know its way out there, but given the holiday period forthcoming, I thought it was time to begin a discussion. Unfortunately, there could another severe weather event, possibly an outbreak, coming up Sunday (November 28) into Monday (November 29).
I am using the 12z and 18z GFS as a guideline for the following information, FYI. Well, a low pressure will probably form somewhere in OK or KS early the day on Sunday, with a 500 mb shortwave trough beginning to dig across this region. The GFS deepens this low quickly as it moves northeast through KS into MO/IA by early Monday. The 500 mb trough will begin to take on a negative tilt Sunday and continue Monday as it slides east. Negative tilted troughs are notorious severe weather producers. VERY strong jet dynamics, perhaps stronger than seen with the outbreak on November 15th, will be present, with a LLJ from the SW at 50-65 knots, a 500 mb jet of 70+ knots, and an upper level jet of 110+ knots. Wind profiles indicate veering with height, a sign of directional shear, with obvious speed shear as well. Surface winds appear to back as well across the warm sector in the boundary layer especially closer to the low pressure as is often the case. This all creates a very favorable shear environment for supercell thunderstorms.
A main question here would be moisture return and instability. GFS is easily progging the warm sector to see 60+ tds, and given rather good performance with this aspect on the 15th event, I have no reason to disagree. Thus, plentiful moist air should be expected within the warm sector south of the warm front and ahead of the cold front.
The current GFS data would storm initiation in the afteroon Sunday across portions of OK, KS, TX, LA into the AR and MO ozarks, with activity spreading east Sunday evening, reaching the Mississippi River about Midnight, then through the lower OH Valley, Middle TN Valley, and AL through Monday Morning, entering GA, eastern KY area Monday Afternoon. GFS appears to show a potent squall line along the front.
Bottom line...I expect a decent and possibly significant chance of severe weather across the Southern Plains, Ozarks, and Arklatex into the MS and Western TN Valley on Sunday Afternoon into Sunday Night, possibly spreading as far north as MO and the western OH Valley. Then this threat extends east through the remainder of the OH, TN Valley on Monday, even affecting some gulf coast states (namely AL and GA). With ample mositure return expected along with very strong wind fields, at the least, a potent squall line with the potential for widespread damaging winds would be expected. With expected shear, and possbile decent instability, supercells and at least a few tornadoes couldn't be ruled out. At this time, I'm not saying this will be as big as last Tuesday's (15th) event yet.
GUT FEELINGS...I think the GFS is a little too far north and maybe a little fast with the low, perhaps a low track from OK into the Ozarks, MO and the lower OH Valley may be more favored. Also again, because of past GFS performance with these events, some slowing by about 12 hours or so may be noted in upcoming GFS runs.
I hope all in the possible threatened areas keep advised to the latest forecasts. Many NWS offices are already talking about severe potential with this system, and expect this to ramp up significantly over the holiday period if models remain this potent with this system.
CORRECTED DATES OF CONCERN IN THE TITLE..
I do want to add that if this system slows as could be the case from what GFS is showing now, the 28th would be the main day of concern.
I am using the 12z and 18z GFS as a guideline for the following information, FYI. Well, a low pressure will probably form somewhere in OK or KS early the day on Sunday, with a 500 mb shortwave trough beginning to dig across this region. The GFS deepens this low quickly as it moves northeast through KS into MO/IA by early Monday. The 500 mb trough will begin to take on a negative tilt Sunday and continue Monday as it slides east. Negative tilted troughs are notorious severe weather producers. VERY strong jet dynamics, perhaps stronger than seen with the outbreak on November 15th, will be present, with a LLJ from the SW at 50-65 knots, a 500 mb jet of 70+ knots, and an upper level jet of 110+ knots. Wind profiles indicate veering with height, a sign of directional shear, with obvious speed shear as well. Surface winds appear to back as well across the warm sector in the boundary layer especially closer to the low pressure as is often the case. This all creates a very favorable shear environment for supercell thunderstorms.
A main question here would be moisture return and instability. GFS is easily progging the warm sector to see 60+ tds, and given rather good performance with this aspect on the 15th event, I have no reason to disagree. Thus, plentiful moist air should be expected within the warm sector south of the warm front and ahead of the cold front.
The current GFS data would storm initiation in the afteroon Sunday across portions of OK, KS, TX, LA into the AR and MO ozarks, with activity spreading east Sunday evening, reaching the Mississippi River about Midnight, then through the lower OH Valley, Middle TN Valley, and AL through Monday Morning, entering GA, eastern KY area Monday Afternoon. GFS appears to show a potent squall line along the front.
Bottom line...I expect a decent and possibly significant chance of severe weather across the Southern Plains, Ozarks, and Arklatex into the MS and Western TN Valley on Sunday Afternoon into Sunday Night, possibly spreading as far north as MO and the western OH Valley. Then this threat extends east through the remainder of the OH, TN Valley on Monday, even affecting some gulf coast states (namely AL and GA). With ample mositure return expected along with very strong wind fields, at the least, a potent squall line with the potential for widespread damaging winds would be expected. With expected shear, and possbile decent instability, supercells and at least a few tornadoes couldn't be ruled out. At this time, I'm not saying this will be as big as last Tuesday's (15th) event yet.
GUT FEELINGS...I think the GFS is a little too far north and maybe a little fast with the low, perhaps a low track from OK into the Ozarks, MO and the lower OH Valley may be more favored. Also again, because of past GFS performance with these events, some slowing by about 12 hours or so may be noted in upcoming GFS runs.
I hope all in the possible threatened areas keep advised to the latest forecasts. Many NWS offices are already talking about severe potential with this system, and expect this to ramp up significantly over the holiday period if models remain this potent with this system.
CORRECTED DATES OF CONCERN IN THE TITLE..
I do want to add that if this system slows as could be the case from what GFS is showing now, the 28th would be the main day of concern.
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