Historic Tornado Outbreak April 27, 2011

[L.B. LaForce]

I love this...right during the week before finals. Good thing is, there looks to be a pretty good threat here on Tuesday night around MI, so maybe i'll get something

[jcwxguy]

A little faster but at this point for the low's to only be apart by half a state, and both be in the same general location is pretty good.

only pretty good? thats awesome considering how far out

[Stebo]

I love this...right during the week before finals. Good thing is, there looks to be a pretty good threat here on Tuesday night around MI, so maybe i'll get something

I hope we get stuff on Monday, because Tuesday Evening I work and as much fun as a High Octane shift is, it would be nice to chase in MI too.

[OceanStWx]

Just took at a look at the GEFS to see what it had to offer for early next week. As others have said details are pointless to discuss at this range, but there are very encouraging signals. Probably most notably is 500 heights.

Definitely a seasonably strong trough ejecting out into the central part of the country, as well as a seasonably strong jet digging down the backside. You can see where the other atmospheric responses then line up (seasonably strong surface reflection, strong LLJ, etc.).

[B-Rent]

I would really like to know what model he is basing that forecast off of

Dr. Forbes doesn't use models. He is the Storm Master G.

Storm Master G

[Radtechwxman]

Dr. Forbes doesn't use models. He is the Storm Master G.

Storm Master G

haha. yes he is. but trust me, he def uses models. impossible to forecast accurate without them

[Srain]

DAY 4-8 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

0359 AM CDT THU APR 21 2011

VALID 241200Z - 291200Z

...DISCUSSION...

WHILE SOME DETAILS VARY...THE 00Z ECMWF/GEFS/UKMET ARE IN AMPLE

GENERAL AGREEMENT WITH THE EXPECTED AMPLIFICATION OF THE LARGE SCALE

PATTERN LATE THIS WEEKEND/EARLY NEXT WEEK...HIGHLIGHTED BY A

PROMINENT WESTERN/CENTRAL CONUS UPPER TROUGH.

ON DAY 4/SUNDAY...THE SOUTHERN HIGH PLAINS WILL LIKELY BE A FOCUS

FOR AT LEAST SOME SURFACE BASED SEVERE THREAT NEAR/EAST OF A DRYLINE

ACROSS WEST TX AND PERHAPS INTO OK. OTHER ELEVATED STORMS CAPABLE OF

SEVERE HAIL ARE PROBABLE SUNDAY NIGHT FROM OK INTO THE OZARKS/LOWER

MO VALLEY. BUT GIVEN LINGERING UNCERTAINTY REGARDING THE EXTENT OF

PRE-DARK SURFACE BASED DEEP CONVECTION...LARGELY OWING TO

ANTICIPATED MODEST LARGE SCALE FORCING FOR ASCENT/ONLY WEAK HEIGHT

FALLS...TOO MUCH UNCERTAINTY CURRENTLY EXISTS TO DELINEATE A 30

PERCENT EQUIVALENT SEVERE RISK AREA.

FOR DAY 5/MONDAY...HAVE INTRODUCED A SEVERE RISK AREA FOR PORTIONS

OF THE SOUTHERN PLAINS TO THE ARKLATEX/OZARKS. WHILE TIMING/SPATIAL

DETAILS VARY TO A DEGREE...REASONABLE CONFIDENCE EXISTS THAT A

SOUTHERN STREAM SHORTWAVE TROUGH WILL OVERSPREAD A MOIST AIRMASS TO

THE EAST OF THE DRYLINE/COLD FRONT. AS SUCH...SEVERE STORMS SEEM

LIKELY MONDAY/MONDAY NIGHT ACROSS THIS REGION.

INTO DAYS 6/7 TUESDAY/WEDNESDAY...AS THE NEXT PORTION OF THE CENTRAL

CONUS UPPER TROUGH PIVOTS EASTWARD...A RELATIVELY

WIDESPREAD/MULTI-ROUND SEVERE THREAT IS EXPECTED FROM THE SOUTHERN

PLAINS EAST-NORTHEASTWARD INTO THE MIDWEST AND LOWER/MIDDLE MS RIVER

VALLEY. WHILE SEVERE STORMS SEEM LIKELY EACH OF THESE

DAYS...SPECIFIC PREDICTABILITY IS STILL QUITE LIMITED IN THIS TIME

FRAME.

..GUYER.. 04/21/2011

[tacoman25]

April 19th, 2003

Well it was def a La Nina year. Doesn't look as strong as this years is though. Thanks for the image

2003 was actually following an El Nino, while this year is following a La Nina. Though by this point both years are closer to neutral.

[Radtechwxman]

2003 was actually following an El Nino, while this year is following a La Nina. Though by this point both years are closer to neutral.

this year has actually been a record La Nina....

[Radtechwxman]

Henry's map for outbreak next week

I really don't know what to expect from this outbreak anymore. I think his map needs to be shifted north. Both the SPC and him are so far south. This low is going to track a lot farther north than previous systems. There seems to be a lot of disagreement

[Radtechwxman]

Per Forbes on FB: MONDAY

Severe thunderstorm and tornado outbreak in central and east TX as far south as Austin and Houston, central and east OK, AR, northwest LA, extreme southeast KS, central and south MO, central and south IL, north, central, and southwest IN, northwest OH.

This is ALOT different than the SPC and what Henry's map is showing

[Radtechwxman]

this forum is dead today. lol. i wanna chat severe weather. wake up!

[cyclone77]

this forum is dead today. lol. i wanna chat severe weather. wake up!

Just now starting to take a real good look at this setup. The latest GFS shows sort of an elongated surface low from northern Missouri down into Oklahoma. Mid and upper winds are fairly backed over the northern portion of the warm sector, so unless we get a stronger northern (closed) low it doesn't look too good further north. As it stands now the best shot for supercell action will be further south where mid and upper winds are more veered. If the mid and upper level jet structure changes, or if the northern low becomes more dominant then this will all change. Still time for some tweaks.

Edited: for my first grade punctuation

[tornadotony]

The 00z GFS is just sick...major severe event from TX to ME Monday-Thursday...unreal...65 dews in Quebec...60-65 in ME and New Brunswick...WTF...

[Radtechwxman]

Just now starting to take a real good look at this setup. The latest GFS shows sort of an elongated surface low from northern Missouri down into Oklahoma. Mid and upper winds are fairly backed over the northern portion of the warm sector, so unless we get a stronger northern (closed) low it doesn't look too good further north. As it stands now the best shot for supercell action will be further south where mid and upper winds are more veered. If the mid and upper level jet structure changes, or if the northern low becomes more dominant then this will all change. Still time for some tweaks.

Edited: for my first grade punctuation

the GFS always shows elongated lows. has been all year. and then the lows end up deepening way more than it showed. so i really am not trusting it. esp since it has been very inconsistent lately. the models are in the time frame where they tend to lose storms and get sloppy with the setup and then a few days later it looks really promising. only time can tell. i still think there will end up being a fairly large area of supercells. but the area of greatest tornado threat, too early to pin down

[nwohweather]

the GFS always shows elongated lows. has been all year. and then the lows end up deepening way more than it showed. so i really am not trusting it. esp since it has been very inconsistent lately. the models are in the time frame where they tend to lose storms and get sloppy with the setup and then a few days later it looks really promising. only time can tell. i still think there will end up being a fairly large area of supercells. but the area of greatest tornado threat, too early to pin down

GFS has been much better as of late however

[jcwxguy]

new outlook

...DISCUSSION... MEDIUM-RANGE MODELS IN FAIRLY GOOD AGREEMENT THROUGH DAY 7 /THU. 4-28/...WITH RESPECT TO A LARGE TROUGH NOW MOVING INTO/DEVELOPING ACROSS THE WRN CONUS. THE TROUGH IS FORECAST TO EJECT/EVOLVE SLOWLY EWD ACROSS THE CENTRAL AND ERN U.S. THROUGH DAY 7...AND AS IT DOES...AN ASSOCIATED SURFACE COLD FRONT WILL ALSO SHIFT SLOWLY EWD ACROSS THIS REGION.

WITH PERSISTENT SLY LOW-LEVEL FLOW AHEAD OF THIS SYSTEM ADVECTING GULF MOISTURE NWD...AMPLE INSTABILITY SHOULD BE AVAILABLE -- BEING ENHANCED EACH AFTERNOON IN CONJUNCTION WITH THE DIURNAL HEATING CYCLE. WITH STRONG MID-LEVEL FLOW ACCOMPANYING THE ADVANCING SYSTEM...SHEAR WILL ALSO BE FAVORABLE FOR ORGANIZED/POTENTIALLY-SEVERE CONVECTION. AS A RESULT...A MULTIPLE-DAY PERIOD OF SEVERE WEATHER IS EXPECTED...WITH THE MAIN THREAT AREA SHIFTING SLOWLY EWD WITH TIME.

WILL HIGHLIGHT A THREAT AREA FROM E TX NWD ACROSS THE ARKLATEX TO ERN OK/WRN AR/SWRN MO FOR DAY 4 /MON. 4-25/...WHERE RELATIVELY SUBSTANTIAL SEVERE WEATHER POTENTIAL IS EVIDENT INCLUDING SUPERCELLS AND SOME THREAT FOR TORNADOES. A SIMILAR THREAT APPEARS POSSIBLE DAY 5...AS THE INITIAL SHORT-WAVE TROUGH EJECTS NNEWD AND A SECOND SHORT-WAVE FEATURE DIGS SEWD TOWARD/INTO THE BASE OF THE LARGER-SCALE TROUGH.

ATTM...SPECIFICS OF THE SEVERE WEATHER THREAT GET MORE DIFFICULT TO DISCERN DAY 6 /WED. 4-27/ AND BEYOND...AS THE FRONT SHIFTS E OF THE MS VALLEY.

[Radtechwxman]

i think those outlooks are way too small and way too south. that really needs to extend way north also with advancing warm sector. the low pressure is heading into the great lakes. makes no sense at all what they are doing

[baroclinic_instability]

i think those outlooks are way too small and way too south. that really needs to extend way north also with advancing warm sector. the low pressure is heading into the great lakes. makes no sense at all what they are doing

If you disagree--please provide your own reasoning/discussion for such disagreement. Do remember these are probabilistic outlooks which take into consideration many other factors besides the operational models alone.

[Radtechwxman]

If you disagree--please provide your own reasoning/discussion for such disagreement. Do remember these are probabilistic outlooks.

I gave my reasoning in my previous comment. the low pressure is set to track up this way. currently looks like it will through eastern iowa and into the great lakes. that will drag the warm front with it northward. yes the best shear, instability, and moisture will prolly line up south, there will most likely be some instability in this area and plenty of upper air dynamics. yes i know it is probabilistic. their outlooks just make it look like the severe weather will only track in the far southern US and i disagree with this

[baroclinic_instability]

I gave my reasoning in my previous comment. the low pressure is set to track up this way. currently looks like it will through eastern iowa and into the great lakes. that will drag the warm front with it northward. yes the best shear, instability, and moisture will prolly line up south, there will most likely be some instability in this area and plenty of upper air dynamics. yes i know it is probabilistic. their outlooks just make it look like the severe weather will only track in the far southern US and i disagree with this

Yes you told us what the operational models were already saying. There is far more to forecasting than that. Do remember we are talking Day 4-5+ here.

[Radtechwxman]

Yes you told us what the operational models were already saying. There is far more to forecasting than that. Do remember we are talking Day 4-5+ here.

yes i know.....i am a meteorology major. i do know these things. but i still disagree with their thinking. we all have opinions

[baroclinic_instability]

yes i know.....i am a meteorology major. i do know these things. but i still disagree with their thinking. we all have opinions

Congrats. We have a lot of met majors here. Opinions are great--but do remember SPC is not putting out outlooks and forecasts to appease their own storm chasing fantasies. Just remember that there are folks at SPC who are pioneers in the field of severe weather and severe weather forecasting.

"makes no sense at all what they are doing"

No--quoting Henry Margusity does not count towards providing your opinions.

[Radtechwxman]

Congrats. We have a lot of met majors here. Opinions are great--but do remember SPC is not putting out outlooks and forecasts to appease their own storm chasing fantasies. Just remember that there are folks at SPC who are pioneers in the field of severe weather and severe weather forecasting.

"makes no sense at all what they are doing"

never said i was going to be right. i have reasoning behind my current thinking. i am not a wishcaster by any means. you just keep stating the obvious. not really necessary. i am going to state my opinion and i love reading what other people say to. i just dont need witty remarks back of things i already know. i am well aware of what the SPC does and aware of the expertise in the forecasting field. doesnt mean i am always going to agree with their forecasts because there arent always right just like many meteorologists and majors, like myself, in the field

[Radtechwxman]

i will be careful with what i write for now on. i shouldnt have said it doesnt make sense with what they were doin. bad choice of wording. i was trying to say i dont agree with their area at the moment.

[thewxmann]

i will be careful with what i write for now on. i shouldnt have said it doesnt make sense with what they were doin. bad choice of wording. i was trying to say i dont agree with their area at the moment.

The SPC usually plays very conservative on their 4-8 day outlooks. The models have been waffling back and forth. Really what they're saying is not "we're not expecting sig svr at XXX location", but "we're not confident enough to outline XXX area".

[jcwxguy]

also good to remember days 4-8 is an area of 30% or higher risk

Note: A severe weather area depicted in the Day 4-8 period indicates a 30% or higher probability for severe thunderstorms within 25 miles of any point.

with the "slight risk" area expanded around that 30% area when its in the days 1-3 outlook.

[Indystorm]

As an interested layman, this recent discussion is reminding me that there is more to forecasting than model hugging, like synoptics.

[Ed Lizard]

They needa 30% prob for Day 4 and beyond, IIRC, which often means smaller areas than one might expect. Reading the texts, they clearly know where severe might happen, even when not colored in, but there is a standard for predictability.

[Hoosier]

also good to remember days 4-8 is an area of 30% or higher risk with the "slight risk" area expanded around that 30% area when its in the days 1-3 outlook.

This. They usually only outline the highest probability areas on days 4-8. Doesn't mean there won't be anything farther north.