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Short-Term Severe/Flooding Discussion


Quincy
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2" hail and 70mph gusts (nws estimate) bearing head on for Oshkosh, NE

edit: New warning 3" hail and 70mph gusts. Very dangerous storm wording added. That cell is going insane

edit2: Now 80mph gusts and baseball size hail. Lordy

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17 minutes ago, mayjawintastawm said:

Pretty nasty cell bearing down on Sterling, CO with baseball size hail and lots of rotation. Looks like a funnel cloud per chaser video. Sterling is the only town of any size in the area.

Tornado, wind, and hail reports in Sterling. The tornado report said that it was in a field, so that's good.

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Already got a cell in SE Wyoming with 50,000 feet echo tops per radarscope. 70 DBZ+ sigs on radar.

Edit as of 4:02: Confirmed tornado.

Tornado Warning for...
  Northwestern Kimball County in the Panhandle of Nebraska...
  Northeastern Laramie County in southeastern Wyoming...

* Until 230 PM MDT.

* At 156 PM MDT, a confirmed tornado was located over Gun Barrel, or
  29 miles northeast of Cheyenne, moving southeast at 40 mph.

  HAZARD...Damaging tornado and hail up to two inches in diameter.

  SOURCE...Emergency Management confirmed tornado near mile marker
           45 of US highway 85.

  IMPACT...Flying debris will be dangerous to those caught without
           shelter. Mobile homes will be damaged or destroyed.
           Damage to roofs, windows, and vehicles will occur.  Tree
           damage is likely.

* The tornado will be near...
  Burns around 220 PM MDT.
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in this area, the late July-August time frame usually has much less shear and less severe weather.

I can see the towering cumulus and anvil clouds 30-70 miles east of me. As you might imagine, there's no way to distinguish between the three cells from this distance. It looks like one mass of clouds.

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  • 3 weeks later...
  • 1 month later...

I like the look of next weekend, particularly the look the GFS is advertising. Both the GFS and the Euro have a seasonably strong trough coming into the west with a 60-70kt 500mb jet over mid/upper 60s dews across much of the plains. Sunday looks to be the biggest day as of right now, but things are going to change. Even then, going off the pattern alone, some sort of severe weather looks probable. 

 

 

7A91E800-E0D7-4F88-AC4E-47A85351C6D8.png

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  • 2 weeks later...
  • 3 weeks later...

Bump... could be a very active day tomorrow in SE TX and LA per SPC

 

Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1226 PM CDT Tue Oct 30 2018

   Valid 311200Z - 011200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM SOUTHEAST
   TEXAS TO THE LOWER MS VALLEY...

   ...SUMMARY...
   Severe thunderstorms, primarily capable of damaging winds and a few
   tornadoes, will be possible from southeast Texas to the lower
   Mississippi Valley Wednesday evening into the overnight. Elsewhere,
   a few severe storms capable of large hail will be possible near the
   Edwards Plateau Wednesday afternoon/evening.

   ...Texas to the Lower Mississippi Valley...
   The large-scale pattern will continue to amplify on Wednesday in
   response to the interaction of a sharp shortwave trough moving into
   west Texas and a secondary mid-level impulse dropping southeast
   across the Rockies. As this occurs, southwesterly 500mb flow will
   increase from east Texas to Mississippi through the overnight. A
   low-level jet will correspondingly intensify from the upper Texas
   coast to the Ohio Valley, with a corridor of at least 50-60 kt
   south/southwesterly winds at 850 mb. Along the western edge of a
   surface ridge centered over the southeast US coast, increasing
   boundary-layer moisture will stream northward across the western
   Gulf, southern Plains, and Mississippi Valley.

   Convection will likely be ongoing across parts of central/northern
   Texas Wednesday morning, generally located near/north of an
   effective cold front stretching from the Big Country northeastward
   to the Arklatex. These cells may be capable of isolated marginally
   severe hail, but should mostly be sub-severe. Through the afternoon,
   the effective front is forecast to drive southward across central
   Texas. While the pre-frontal environment in this area will be
   conditionally favorable for all severe hazards, deep-layer shear
   vectors suggest most cells will be undercut by the front, limiting
   the wind/tornado potential. Therefore, the Enhanced risk has been
   contracted some here. Conversely, the Slight risk has been expanded
   westward towards the Edwards Plateau, where the primary shortwave
   trough and strong effective shear may encourage a few elevated
   storms capable of large hail during the afternoon and evening.

   The highest potential for impactful severe weather will likely exist
   from southeast Texas towards the lower Mississippi Valley during the
   evening and overnight. In conjunction with the aforementioned
   low-level jet, channels of warm/moist low-level confluence streaming
   north off the Gulf will probably encourage discrete development
   ahead of a southwest/northeast-oriented line of strong/severe storms
   moving east across the Sabine Valley during the evening. Forecast
   soundings indicate ample low-level shear for stronger circulations
   within both discrete/line-embedded supercells and QLCS structures,
   with this potential likely maximized across portions of
   western/central Louisiana and western Mississippi. Although
   instability will be modest, enough low-level CAPE should be
   available for a threat of tornadoes (a couple of which could be
   strong) and damaging winds, especially considering surface dew
   points in the upper 60s/lower 70s. Indeed, HREF guidance indicates
   high probabilities of at least 500 J/kg of surface-based CAPE
   extending to the Mississippi Delta. Considering this fairly
   consistent signal from large-scale and hi-res guidance, the
   Enhanced/Slight risks have been expanded eastward for a nocturnal
   threat of tornadoes and damaging winds.

   ...MAXIMUM RISK BY HAZARD...
   Tornado:  10% SIG - Enhanced
   Wind:     30%     - Enhanced
   Hail:     15%     - Slight

   ..Picca.. 10/30/2018
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The more problematic event might be early next week with a very favorable 500 mb pattern for a larger scale severe episode across the S US showing up on the ensembles. Going to hinge on how much moisture return can take place since there could be a FROPA or two through the Gulf prior to then, but that definitely looks to be something to watch especially since it may fall on Election Day.

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ZCZC SPCPWOSPC ALL
   WOUS40 KWNS 312010
   LAZ000-MSZ000-TXZ000-010200-

   PUBLIC SEVERE WEATHER OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0310 PM CDT WED OCT 31 2018

   ...Severe thunderstorms expected over parts of the lower Mississippi
   Valley this evening and overnight...

   * LOCATIONS...
     Louisiana
     Southern and Central Mississippi
     East Texas

   * HAZARDS...
     A few intense tornadoes
     Scattered damaging winds
     Isolated large hail

   * SUMMARY...
     The greatest risk for severe thunderstorms, capable of producing
     damaging winds, hail, and tornadoes, exists from southeast Texas
     to the lower Mississippi Valley through tonight.

   Preparedness actions...

   Tornadoes at night can be particularly dangerous because they 
   are usually fast-moving and difficult to see. Stay tuned to
   NOAA Weather Radio, weather.gov, or other media for watches and
   warnings. A tornado watch means that conditions are favorable
   for tornadoes to form during the next several hours. If a tornado
   warning is issued for your area, move to a place of safety,
   ideally in a basement or interior room on the lowest floor of a
   sturdy building.

   &&

   ..Gleason.. 10/31/2018
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ww0416_radar_big.gif

 

URGENT - IMMEDIATE BROADCAST REQUESTED
   Tornado Watch Number 416
   NWS Storm Prediction Center Norman OK
   300 PM CDT Wed Oct 31 2018

   The NWS Storm Prediction Center has issued a

   * Tornado Watch for portions of 
     Southwestern Arkansas
     Northwestern Louisiana
     Extreme southeastern Oklahoma
     Much of east Texas
     Coastal Waters

   * Effective this Wednesday afternoon and evening from 300 PM
     until 1000 PM CDT.

   * Primary threats include...
     A few tornadoes likely
     Scattered damaging wind gusts to 70 mph likely
     Scattered large hail events to 1.5 inches in diameter possible

   SUMMARY...Thunderstorms will increase in coverage/intensity through
   the evening along a cold front across central and northeastern
   Texas, while other storms will continue to form ahead of the front
   across southeastern Texas.  The storm environment will become more
   favorable for rotating storms through the evening, with an attendant
   threat for a few tornadoes, damaging winds, and isolated large hail.

   The tornado watch area is approximately along and 75 statute miles
   east and west of a line from 35 miles north northeast of Texarkana
   AR to 70 miles west southwest of Houston TX. For a complete
   depiction of the watch see the associated watch outline update
   (WOUS64 KWNS WOU6).

   PRECAUTIONARY/PREPAREDNESS ACTIONS...

   REMEMBER...A Tornado Watch means conditions are favorable for
   tornadoes and severe thunderstorms in and close to the watch
   area. Persons in these areas should be on the lookout for
   threatening weather conditions and listen for later statements
   and possible warnings.

   &&

   AVIATION...Tornadoes and a few severe thunderstorms with hail
   surface and aloft to 1.5 inches. Extreme turbulence and surface wind
   gusts to 60 knots. A few cumulonimbi with maximum tops to 500. Mean
   storm motion vector 24030.

   ...Thompson
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mcd1602.gif

Mesoscale Discussion 1602
   NWS Storm Prediction Center Norman OK
   0355 PM CDT Wed Oct 31 2018

   Areas affected...central Arkansas

   Concerning...Severe potential...Watch possible 

   Valid 312055Z - 312230Z

   Probability of Watch Issuance...60 percent

   SUMMARY...Storms may increase in intensity this evening, with a
   threat of isolated tornadoes.

   DISCUSSION...A slow-moving front currently extends from northeast AR
   to just north of LZK to west of TXK. South of this boundary, a moist
   air mass exists and is gradually warming due to advection. MUCAPE is
   currently around 1500-2000 j/kg, with effective SRH on the order of
   100-150 m2/s2 per LZK VWP.

   Shear profiles are forecast to increase a bit this evening in
   advance of the upper trough, with 850 flow around 40 kt. This will
   result in hodographs favoring supercells, and a tornado or two may
   occur. As such, a watch may need to be considered soon.

   ..Jewell/Thompson.. 10/31/2018

   ...Please see www.spc.noaa.gov for graphic product...

   ATTN...WFO...MEG...LZK...SHV...
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Tornado Warning
TXC015-157-473-312145-
/O.NEW.KHGX.TO.W.0012.181031T2102Z-181031T2145Z/

BULLETIN - EAS ACTIVATION REQUESTED
Tornado Warning
National Weather Service Houston/Galveston TX
402 PM CDT WED OCT 31 2018

The National Weather Service in League City has issued a

* Tornado Warning for...
  Southeastern Austin County in southeastern Texas...
  Northwestern Fort Bend County in southeastern Texas...
  Southeastern Waller County in southeastern Texas...

* Until 445 PM CDT.

* At 402 PM CDT, a storm with a history of a confirmed tornado was
  located near Sealy, moving northeast at 20 mph.

  HAZARD...Damaging tornado.

  SOURCE...Emergency Management confirmed tornado.

  IMPACT...Flying debris will be dangerous to those caught without
           shelter. Mobile homes will be damaged or destroyed.
           Damage to roofs, windows, and vehicles will occur.  Tree
           damage is likely.

* The tornado will be near...
  San Felipe around 410 PM CDT.
  Simonton around 415 PM CDT.
  Northern Weston Lakes around 425 PM CDT.
  Pattison around 430 PM CDT.
  Brookshire and Fulshear around 435 PM CDT.
  Katy around 445 PM CDT.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

To repeat, a tornado is on the ground. TAKE COVER NOW! Move to a
basement or an interior room on the lowest floor of a sturdy
building. Avoid windows. If you are outdoors, in a mobile home, or in
a vehicle, move to the closest substantial shelter and protect
yourself from flying debris.

&&

LAT...LON 2996 9589 2979 9583 2978 9581 2970 9577
      2966 9609 2973 9617
TIME...MOT...LOC 2102Z 243DEG 16KT 2972 9608

TORNADO...OBSERVED
HAIL...<.75IN

$$
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ww0417_radar_big.gif

 

URGENT - IMMEDIATE BROADCAST REQUESTED
   Tornado Watch Number 417
   NWS Storm Prediction Center Norman OK
   410 PM CDT Wed Oct 31 2018

   The NWS Storm Prediction Center has issued a

   * Tornado Watch for portions of 
     Central and southeastern Arkansas

   * Effective this Wednesday afternoon from 410 PM until Midnight
     CDT.

   * Primary threats include...
     A couple tornadoes possible
     Scattered damaging wind gusts to 70 mph possible
     Scattered large hail events to 1.5 inches in diameter possible

   SUMMARY...Thunderstorms will increase through the evening from
   southwestern into central Arkansas, and then storms will spread
   eastward through the early overnight hours.  The storm environment
   will gradually become more favorable for rotating storms, with an
   attendant threat for a couple of tornadoes, damaging winds, and
   isolated large hail.

   The tornado watch area is approximately along and 75 statute miles
   east and west of a line from 70 miles south southwest of Hot Springs
   AR to 45 miles northeast of Little Rock AR. For a complete depiction
   of the watch see the associated watch outline update (WOUS64 KWNS
   WOU7).

   PRECAUTIONARY/PREPAREDNESS ACTIONS...

   REMEMBER...A Tornado Watch means conditions are favorable for
   tornadoes and severe thunderstorms in and close to the watch
   area. Persons in these areas should be on the lookout for
   threatening weather conditions and listen for later statements
   and possible warnings.

   &&

   OTHER WATCH INFORMATION...CONTINUE...WW 416...

   AVIATION...Tornadoes and a few severe thunderstorms with hail
   surface and aloft to 1.5 inches. Extreme turbulence and surface wind
   gusts to 60 knots. A few cumulonimbi with maximum tops to 500. Mean
   storm motion vector 24035.

   ...Thompson
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ww0418_radar_big.gif

 

URGENT - IMMEDIATE BROADCAST REQUESTED
   Tornado Watch Number 418
   NWS Storm Prediction Center Norman OK
   810 PM CDT Wed Oct 31 2018

   The NWS Storm Prediction Center has issued a

   * Tornado Watch for portions of 
     Southern Arkansas
     Louisiana
     Western Mississippi
     Coastal Waters

   * Effective this Wednesday night and Thursday morning from 810 PM
     until 400 AM CDT.

   * Primary threats include...
     A few tornadoes likely with a couple intense tornadoes possible
     Scattered damaging wind gusts to 70 mph likely
     Isolated large hail events to 1.5 inches in diameter possible

   SUMMARY...Conditions will continue to become increasingly favorable
   for supercells and bowing segments along and ahead an
   east/northeastward-moving convective line. Very strong low-level
   shear coincident with a moist air mass will support the possibility
   of damaging winds and tornadoes, a couple of which could be strong.

   The tornado watch area is approximately along and 60 statute miles
   east and west of a line from 40 miles east northeast of El Dorado AR
   to 30 miles southeast of Lake Charles LA. For a complete depiction
   of the watch see the associated watch outline update (WOUS64 KWNS
   WOU8).

   PRECAUTIONARY/PREPAREDNESS ACTIONS...

   REMEMBER...A Tornado Watch means conditions are favorable for
   tornadoes and severe thunderstorms in and close to the watch
   area. Persons in these areas should be on the lookout for
   threatening weather conditions and listen for later statements
   and possible warnings.
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If the Euro is on the right track (and it has been fairly steady), we could be dealing with a very significant severe weather event Monday evening continuing into Tuesday afternoon from E Texas and SE Oklahoma extending into AL and GA.

Sampling one of the parameter spaces at 06z in along the I-55 corridor in MS reveals SBCAPE of 1000-2000+ J/kg, deep layer shear of 60-70 kts and low level shear in places in excess of 50 kts (this type of environment is generally in place through the whole period in one place or another). This would be an environment capable of long lived supercells with significant tornadoes. Moreover, this trough is quite low amplitude (compared to its wavelength) and would likely portend a long period of discrete/semi-discrete storm mode.

Extent of the threat will be dependent on moisture return of course, but it is important to note that notable destabilization in this case will occur nearly independent of the diurnal cycle given the strong advective processes (WAA, moist advection) vs. diabatic insolation.

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