3137 replies to this topic

[tennessee storm chaser]

well after glancing at the 0zgfs, it holds serve on a big time severe weather outbreak next week... seems like its going to come in two waves both look very dynamic fueled. the second one seems stronger. late tuesday into wed. timeframe. still very axious to hear mr. freds thoughts.

[smokedevil]

Interesting wording from Meg...

I DON`T PUT A LOT OF FAITH IN
INSTABILITY PARAMETERS PAST THE FIRST FEW FORECAST PERIODS...BUT
FROM AN OVERALL PATTERN STANDPOINT BOTH JET DYNAMICS AND MOISTURE
FIELDS LOOK SUPPORTIVE OF SEVERE WEATHER. LONG CURVED HODOGRAPHS
SHOULD BE SUPPORTIVE OF LARGE HAIL...DAMAGING WIND AND
TORNADOES...ESPECIALLY WEDNESDAY.

[trency911]

Hodographs are pretty nasty looking.

[trency911]

12Z GFS is rolling in.  GFS develops an ULL over Kansas/Missouri border and tracks it to southern Michigan, with the surface low tracking from central OK into the lower Ohio Valley.  Strong vortex max and negative tilted trough pulls in a warm, moist airmass across the region with 60 Tds moving into the southern OH/IN/IL 12Z Wed with 65 Tds across a good majority of the Deep South/Southeast.  There are even pockets of 70 Tds nosing north from southeastern MS into northwestern Alabama as the low continues to wrap up.  A strong low level jet over 55Kts at 850MB with a 100KT jet streak at 500MB.  SFC-500 MB shear AOA 80Kts along the front supports the potential for another widespread damaging wind event with embedded supercells possible.  Hodographs impressive ahead of the front with clockwise signatures, if any storm forms ahead of the line they could go tornadic quite easily especially given low LCL/LFC.

Still 5 days out though...

Edited by trency911, 22 April 2011 - 02:21 PM.

[ARCC]

Everything looks really good for a tornado outbreak. Strong instability, subtile forcing with the positive/neutral tilt trough, good dry slot at 700mb. However, the one thing right now I see changes that is the fact that according to the 12z GFS, winds are uni-directional at the surface to 850mb. We need the winds to back to the south more to get a good tornado outbreak.

[mwbwhorton]

i know things can change but our local tv mets seem a little worried about this system they all said Tuesday needs to be watched carefully and could be a especially dangerous day....unusual wording for them as they tend to be conservative.

[djbarker]

Conservatism tends to go out the window when there's been a pattern of destructive severe weather outbreaks.

[trency911]

BMX:

Quote

THE BIG EVENT IS STILL SHAPING UP FOR TUESDAY AND WEDNESDAY. THERE
IS FAIRLY GOOD MODEL CONSENSUS WITH REGARD TO TIMING AND POSITION
OF SURFACE FEATURES. THERE STILL APPEARS TO BE TWO WAVE OF STORMS
THAT WILL AFFECT THE AREA. THE FIRST WAVE MAY BE MORE OF A HEAVY
RAIN EVENT...AS FIRST LINE OF STORMS SLOWS WEAKENS AND BECOMES
STATIONARY OVER NW ALABAMA ON TUESDAY. THERE WILL BE ENOUGH
INSTABILITY AND SHEAR FOR THE POSSIBILITY OF SEVERE STORMS...BUT
BETTER FORCING AND SHEAR WILL HAPPEN ON WEDNESDAY AS UPPER LOW
AND SURFACE LOW DEEPENS UPSTREAM OF ALABAMA. THE SQUALL LINE AND
COLD FRONT SHOULD BE MOVING ACROSS CENTRAL ALABAMA WEDNESDAY
NIGHT...AND FORECAST HIGHEST RAIN CHANCES DURING THIS TIME
PERIOD. THE COLD FRONT WILL MOVE THROUGH FAIRLY QUICKLY AS SHORT
WAVE TROF BECOMES NEGATIVELY TILTED AND RAIN SHOULD BE OUT OF
CENTRAL ALABAMA BY SUNRISE THURSDAY...WITH MUCH COOLER AND DRIER
CONDITIONS THURSDAY AND FRIDAY.

[tennessee storm chaser]

this pattern we have been in for few weeks and what looks like another buisy week or so ahead... its starting to remind me of the may of 2003 pattern somewhat.

[trency911]

Quote

Dr. Greg Forbes Tue Apr 26. Severe thunderstorms and tornado outbreak in southeast MI, OH,
east and south IN, OH, west and central PA, west and central NY, west MD,
WV, southwest and north VA, DC, TN, KY, north GA, north half AL, north and
central MS, north LA, northeast TX, AR, south MO, southeast and south-central
KS, north and east OK.

[tennessee storm chaser]

yep, forbes is really concerned about tornadoes with that 2nd system next week. people in the midsouth, tennesee valleys. deep south need to be on their toes next week.

[TimHSV]

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEMPHIS TN
ISSUED 352 PM CDT FRI APR 22 2011

Edited for specifics:


DISCUSSION...FORECAST FOCUS ON SEVERE POTENTIAL TONIGHT...THEN ON
TWO SYSTEMS NEXT WEEK THAT COULD BRING SIGNIFICANT RAINFALL AND
SEVERE WEATHER.


THE FRONT WILL MORE OR LESS REMAIN STATIONARY UNTIL LATE THIS
WEEKEND AS A PRETTY POTENT SYSTEM FORMS IN THE SOUTHERN PLAINS
AND FORCES THE FRONT FURTHER NORTH. SEVERAL MCS/S WILL DEVELOP
ALONG THE FRONT BETWEEN NOW AND SUNDAY NIGHT...PRODUCING
POTENTIALLY CATASTROPHIC AMOUNTS OF RAINFALL /8+ INCHES/ OVER
MISSOURI INTO SOUTHERN ILLINOIS. THE MIDSOUTH WILL BE ON THE FAR
SOUTHERN FRINGES OF THIS ACTIVITY...SO POPS WILL GENERALLY BE LOW
FOR THE REMAINDER OF THIS PERIOD. CONSULT THE LONG TERM DISCUSSION
FOR CONSEQUENCES OF THIS HEAVY RAINFALL FOR THE MIDSOUTH RIVERS.

.LONG TERM...MONDAY THROUGH NEXT FRIDAY.

EARLY PORTIONS OF NEXT WEEK WILL HAVE TO DEAL WITH MULTIPLE SEVERE
WEATHER EVENTS AND HEAVY RAIN/FLASH FLOODING...FOLLOWED BY LONG
DURATION AND SIGNIFICANT RIVER FLOODING POSSIBLE AS THE WATER FROM
UPSTREAM WORKS DOWN THE MISSISSIPPI LATER NEXT WEEK.

Edited by TimHSV, 22 April 2011 - 10:47 PM.

[trency911]

TimHSV, on 22 April 2011 - 10:39 PM, said:

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEMPHIS TN
ISSUED 352 PM CDT FRI APR 22 2011

Edited for specifics:

Yea flooding is going to be a great concern.

[skywatcher22]

Tuesday's severe threat has the potential to be exceptionally bad with a similar jet structure to the 4/15 event. I would not be surprised to see a High Risk across NE TX, SE OK, and much of AR near a warm front.

Edited by Matt Grantham, 22 April 2011 - 11:26 PM.

[TimHSV]

Matt Grantham, on 22 April 2011 - 11:25 PM, said:

Tuesday's severe threat has the potential to be exceptionally bad with a similar jet structure to the 4/15 event. I would not be surprised to see a High Risk across NE TX, SE OK, and much of AR near a warm front.

Yea Matt I just had time to look at the 12Z ECMWF and it really is cranking the 850mb Jet near 65-70knts across E.AR/ W TN /N MS.along with a 95knt 500mb jet coming in out of the SW by 12Z Wed., and the 500mb trof it shows coming acorss OK is really deep and powerful it looks at this time.

Edited by TimHSV, 22 April 2011 - 11:38 PM.

[tennessee storm chaser]

TimHSV, on 22 April 2011 - 11:32 PM, said:

Yea Matt I just had time to look at the 12Z ECMWF and it really is cranking the 850mb Jet near 65-70knts across E.AR/W TN/N MS. by 12Z Wed., and the 500mb trof it shows coming acorss OK is really deep and powerful it looks at this time.

yeah, yall the 0zgfs is quite frighting. the 114 hour looks to be super cells hammering east ar. and west tn. very nice strong ll jet cranking that late tuesday evening

[ARCC]

Scary look for MS,AL,Ga and TN. All that really can be said.

[TimHSV]

tennessee storm chaser, on 22 April 2011 - 11:38 PM, said:

yeah, yall the 0zgfs is quite frighting. the 114 hour looks to be super cells hammering east ar. and west tn. very nice strong ll jet cranking that late tuesday evening

10-4 there...

[skywatcher22]

I've drawn the surface features (dryline and warm front) on top of the 300 mb map. What really scares me is the jet nosing in just south and parallel to the warm front as depicted. That could lead to strong backing of the surface winds as the surface low deepens and the pressure trough along the warm front sharpens. This same forcing traditionally leads the development of explosive convection.

Edited by Matt Grantham, 22 April 2011 - 11:56 PM.

[TimHSV]

ARCC, on 22 April 2011 - 11:52 PM, said:

Scary look for MS,AL,Ga and TN. All that really can be said.

I'll say. Bounadary layer looks ripe and jet structure's looks very well defined, with SRH averages around 450-550m^2/s^2, and EHI's average 4-6.

Edited by TimHSV, 22 April 2011 - 11:59 PM.

[TimHSV]

Matt Grantham, on 22 April 2011 - 11:55 PM, said:

I've drawn the surface features (dryline and warm front) on top of the 300 mb map. What really scares me is the jet nosing in just south and parallel to the warm front as depicted. That could lead to strong backing of the surface winds as the surface low deepens and the pressure trough along the warm front sharpens. This same forcing traditionally leads the development of explosive convection.

Wow, 120knts. AR/ Western TN/ Northern MS. just looks very dangerous at this point.

Edited by TimHSV, 23 April 2011 - 12:04 AM.

[ARCC]

TimHSV, on 22 April 2011 - 11:58 PM, said:

I'll say. Bounadary layer looks ripe and jet structure's looks very well defined, with SRH averages around 450-550m^2/s^2, and EHI's average 4-6.

Lift would be incredible over AL,MS and GA in this setup. Add in a decent cap and dry air at 700mb to hold off the junk convection. Add in subtle forcing and good helicity. You then have a perfect setup for explosive supercells and long tracked tornadoes. What a setup. Deep ridge over the Atlantic gives me the idea that the GFS could be under doing moisture and instability as well.

Edited by ARCC, 23 April 2011 - 12:04 AM.

[TimHSV]

ARCC, on 23 April 2011 - 12:04 AM, said:

Lift would be incredible over AL,MS and GA in this setup. Add in a decent cap and dry air at 700mb to hold off the junk convection. Add in subtle forcing and good helicity. You then have a perfect setup for explosive supercells and long tracked tornadoes. What a setup. Deep ridge over the Atlantic gives me the idea that the GFS could be under doing moisture and instability as well.

Yea ARCC, I was gonna type did you see that 700mb dry punch

[storm5]

What are the chances this trends away from being such  an  explosive event??

[mwbwhorton]

i can only imagine the SPC's thinking on this with these latest models given what's already happened tonight and over the last week or so....

Edited by mwbwhorton, 23 April 2011 - 12:09 AM.

[skywatcher22]

ARCC, on 23 April 2011 - 12:04 AM, said:

Lift would be incredible over AL,MS and GA in this setup. Add in a decent cap and dry air at 700mb to hold off the junk convection. Add in subtle forcing and good helicity. You then have a perfect setup for explosive supercells and long tracked tornadoes. What a setup. Deep ridge over the Atlantic gives me the idea that the GFS could be under doing moisture and instability as well.

What do you mean by incredible lift, but subtle forcing?

IMO it looks like the forcing is quite strong and linear by 114-120 hours. Mainly a big squall line with maybe a few cells out ahead.

[ARCC]

storm5, on 23 April 2011 - 12:08 AM, said:

What are the chances this trends away from being such  an  explosive event??

The chances are there of course, after all it happened a few weeks ago. However, with both GFS and Euro showing a nasty event, you have to think it holds a pretty good shot at happening.

[skywatcher22]

storm5, on 23 April 2011 - 12:08 AM, said:

What are the chances this trends away from being such  an  explosive event??

It honestly doesn't look all that explosive for Alabama, although there still will be severe weather. Tuesday looks like the worst day from SE OK/NE TX into AR and western TN/KY.

Edited by Matt Grantham, 23 April 2011 - 12:40 AM.

[tennessee storm chaser]

the 0z euro has the sl a tad more north. that would get the warm sector farther north. that could lead to higher dews. mid 60s to upper 60s across much of the region. painting a severe weather event to say the least.

[weatherguy]

SUBSTANTIAL SEVERE WEATHER POTENTIAL IS EXPECTED TO SHIFT SLOWLY EWD
   ACROSS THE ERN U.S. DAYS 4-6 /TUE. 4-26 THROUGH THU. 4-28/...AS A
   LARGE UPPER TROUGH PROGRESSES FROM THE CENTRAL U.S. DAY 4 ACROSS THE
   MS VALLEY DAY 5...AND THEN ON EWD THROUGH DAYS 6/7.  MODEL
   DIFFERENCES WITH RESPECT TO TIMING OF THIS FEATURE BEGIN TO EMERGE
   DAY 5...BUT BECOME INCREASINGLY PRONOUNCED THROUGH DAYS 6 AND 7 AS
   THE TROUGH APPROACHES THE E COAST STATES/ERN ATLANTIC.
  
THE THREAT SHOULD SHIFT E OF THE MS VALLEY INTO THE MID
   SOUTH/SOUTHEAST DAY 5...AS THE SHORT-WAVE FEATURE TAKES ON A NEUTRAL
   TO EVEN NEGATIVE TILT AS IT CROSSES THIS REGION.  AGAIN -- AMPLY
   UNSTABLE AIRMASS COMBINED WITH THE STRENGTH OF THE UPPER SYSTEM AND
   ASSOCIATED FLOW FIELD SUGGESTS WIDESPREAD SEVERE WEATHER CAN BE
   EXPECTED...INCLUDING THE POTENTIAL FOR TORNADOES.

Edited by andyhb, 28 December 2012 - 04:34 PM.