STORM2K

OK, I have been hearing rumors of a potential severe weather
outbreak for the South, this next weekend (Feb. 24-25)....

Any thoughts or observations?

~Annette~

It's the talk of weather forums all around.

Both the GFS and ECMWF (the major global models) show a setup that is condusive for an expansive, broad warm sector characterized by extreme deep-layer (140 kt at 500mb) and low-level (70 kt at 850mb) shear. Couple that with temperatures at 500mb of -15°C and dewpoints of 60 all the way to areas with extensive snowcover at this time, and we've a recipe for an expansive severe wx outbreak, from the Gulf Coast all the way to the Great Lakes, and from the Plains all the way east to the Appalachians.

All this is a result of a low which bombs from 990 mb to 975 mb, and a strong 500mb longwave trough, as progged by both the GFS and ECMWF. Such a scenario is analogous to what occurred on April 3, 1974.

Again, not hyping anything, but what I and others have seen on the models, is similar of some serious, historic outbreaks in the past. Could this change? Of course. (Thankfully, it's still a week out.) But the fact that two major models and their ensembles have been seeing this system for a week now already, signals that this could be a high-impact system that could be on tap.

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0305 AM CST SUN FEB 18 2007

VALID 211200Z - 261200Z

MEDIUM RANGE MODELS ARE IN GENERAL AGREEMENT DURING THE LATER HALF
OF THE UPCOMING WEEK. THE MODELS DEVELOP A VIGOROUS UPPER-LEVEL
TROUGH OVER THE WRN U.S. MOVING THE TROUGH ACROSS THE ROCKIES ON
FRIDAY AND INTO THE PLAINS SATURDAY. AHEAD OF THE APPROACHING
SYSTEM...A STRONG LOW-LEVEL JET WILL TRANSPORT MOISTURE NWD INTO THE
PLAINS AND MS VALLEY. ALTHOUGH THE TIMING OF THE APPROACHING SYSTEM
REMAINS QUESTIONABLE...DAY 6 AND DAY 7 LOOK TO HAVE THE MOST
POTENTIAL FOR SEVERE WEATHER. IF SUBSTANTIAL INSTABILITY DEVELOPS AS
FORECAST FRIDAY...A SIGNIFICANT SEVERE WEATHER EVENT COULD OCCUR IN
THE PLAINS AND OZARK REGION. THIS WOULD LIKELY CONTINUE INTO
SATURDAY AS THE TROUGH TRANSITIONS EWD ACROSS THE MS...TN AND OH
VALLEYS.

..BROYLES.. 02/18/2007

This is so far out to make a prediction, but the early signs say this could be BAD. How bad? Hard to say.

wxmann_91 wrote:It's the talk of weather forums all around.

Both the GFS and ECMWF (the major global models) show a setup that is condusive for an expansive, broad warm sector characterized by extreme deep-layer (140 kt at 500mb) and low-level (70 kt at 850mb) shear. Couple that with temperatures at 500mb of -15°C and dewpoints of 60 all the way to areas with extensive snowcover at this time, and we've a recipe for an expansive severe wx outbreak, from the Gulf Coast all the way to the Great Lakes, and from the Plains all the way east to the Appalachians.

All this is a result of a low which bombs from 990 mb to 975 mb, and a strong 500mb longwave trough, as progged by both the GFS and ECMWF. Such a scenario is analogous to what occurred on April 3, 1974.

Again, not hyping anything, but what I and others have seen on the models, is similar of some serious, historic outbreaks in the past. Could this change? Of course. (Thankfully, it's still a week out.) But the fact that two major models and their ensembles have been seeing this system for a week now already, signals that this could be a high-impact system that could be on tap.

You're saying Super Outbreak II?

CrazyC83 wrote:

wxmann_91 wrote:It's the talk of weather forums all around.

Both the GFS and ECMWF (the major global models) show a setup that is condusive for an expansive, broad warm sector characterized by extreme deep-layer (140 kt at 500mb) and low-level (70 kt at 850mb) shear. Couple that with temperatures at 500mb of -15°C and dewpoints of 60 all the way to areas with extensive snowcover at this time, and we've a recipe for an expansive severe wx outbreak, from the Gulf Coast all the way to the Great Lakes, and from the Plains all the way east to the Appalachians.

All this is a result of a low which bombs from 990 mb to 975 mb, and a strong 500mb longwave trough, as progged by both the GFS and ECMWF. Such a scenario is analogous to what occurred on April 3, 1974.

Again, not hyping anything, but what I and others have seen on the models, is similar of some serious, historic outbreaks in the past. Could this change? Of course. (Thankfully, it's still a week out.) But the fact that two major models and their ensembles have been seeing this system for a week now already, signals that this could be a high-impact system that could be on tap.

You're saying Super Outbreak II?

I would be foolish to say that. Setup does sorta look similar, but many little details still have to be sorted out. Everything has to go perfectly right for a Super Outbreak II, and in severe wx setups, that's nearly impossible.

Of course, given the setup, in this case, we could still have several little things go wrong and the outbreak still be a historic one.

If this happens, I think next Saturday will see most of the action.

It will be very interesting to see how this pans out.

my local mets here are telling folks that if they do not have a weather radio, to purchase one. also, i'm in the fire dept. here, and we have been informed of the possibility of VERY severe weather in the friday or saturday time frame. I also noticed that they were checking the warning sirens in my town sunday, something they never do....the last time I can remember folks here acting as concerned as they are now, was in may, 2004.

From Jackson, Ms NWS.

BY SATURDAY THE LARGE PROGRESSIVE DISTURBANCE REFERRED TO ABOVE
SHOULD BE MOVING THROUGH THE HEART OF THE NATION...PROBABLY
ACHIEVING AN OMINOUS "NEGATIVE TILT". GENERAL AGREEMENT ON THE
STRENGTH AND POSITIONING OF THIS FEATURE IS VERY HIGH AMONG
AVAILABLE MODELS AND ASSOCIATED ENSEMBLES...ALTHOUGH THERE ARE MINOR
DISCREPANCIES IN TIMING. EXPECTED SURFACE LOW DEVELOPMENT NEAR THE
MISSOURI VALLEY WILL DEFINITELY BE CLOSE ENOUGH TO WARRANT A RISK OF
SEVERE WEATHER OVER THE ARKLAMISS...CONSIDERING ADEQUATE LOW LEVEL
MOISTURE SHOULD BE IN PLACE AND THE OFTEN CRITICAL 570 DM 500 MB
HEIGHT CONTOUR WILL LIE ACROSS THE CWA. STILL QUITE A FEW QUESTION
MARKS...SUCH TIMING...TO BE ANSWERED OVER THE COMING DAYS...BUT
THERE IS ENOUGH CONFIDENCE THAT A SEVERE WEATHER OUTBREAK COULD
HAPPEN IN THE VICINITY TO BEGIN MENTIONING POTENTIAL IN THE HWO.

Well, this wind that is cranking here today from the south is not good news. We should have 5 days of southerly winds to transport up moisture. That is usually a problem this time of year, but it doesn't look to be as big of an issue this time.

Tennesseestorm wrote:It will be very interesting to see how this pans out.

Welcome to the board Tennesseestorm.




As always, instability will be the issue; dynamics looks really good with 70 kt still progged at H85, along with a 100 kt mid-level jet streak.

From what I'm gathering at EasternUSWX this system is falling apart fast.

conestogo_flood wrote:From what I'm gathering at EasternUSWX this system is falling apart fast.

How can it when it hasn't even developed yet?

Norman, OK hasn't given up on it, yet - fingers are still pointing this way.

I, too, have seen alot of encouragement to folks to buy weather radios,
this week. I'll be watching this system, closely.

~Annette~

conestogo_flood wrote:From what I'm gathering at EasternUSWX this system is falling apart fast.

No it has not. And I apologize if my post there had such a tone. Significant, major, or even possibly historic outbreak still looks to be tap for this weekend.

breeze wrote:Norman, OK hasn't given up on it, yet - fingers are still pointing this way.

I, too, have seen alot of encouragement to folks to buy weather radios,
this week. I'll be watching this system, closely.

~Annette~

My NWS, Omaha area, is even hinting at it. They said in Feb. 19's late afternoon discussion, they are concerned with 1000 CAPE and high shear values. Could be interesting if this thing slows down and deepens.

WAA occuring along the coast, with winds coming in off the Gulf. Last night's low was 27*F (at my home), and I'd be very surprised if we dropped much lower than the present temperature of 53*F. We'll be near 80*F by Ash Wednesday. There will be plenty of juicy Gulf air to work with, so yeah, I'm paying close attention now.

From what i'm hearing, the 12z gfs has brought it back strong again, but I have not personally seen it.

Local mets have mentioned the possibility of a significant outbreak this weekend.

Also Dr. Greg Forbes said that there was the potential for "dozens of tornadoes" this weekend.

Reading Forecast Discussions, instability may end up being the inhibiting factor for an outbreak..

The SPC is very bullish already for Friday (Day 3) with a 30-hatched, and that is only the beginning.

They mention upgrades without being specific. I think this could be only the second time we see back-to-back-to-back HIGH risk days...