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andyhb

April 26th-30th, 2014 Major Tornado Outbreak

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Chasers may have a bit of a dilemma for Monday.  Greater severe potential should be down south but a 30% area in relatively chaser-friendly Illinois.

 

 

 

 

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   DAY 2 CONVECTIVE OUTLOOK     NWS STORM PREDICTION CENTER NORMAN OK   0100 AM CDT SUN APR 27 2014   VALID 281200Z - 291200Z   ...THERE IS A MDT RISK OF SVR TSTMS ACROSS PORTIONS OF   MS/AL/TN/LA...   ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE MID-SOUTH/MIDWEST TO   THE OH RIVER VALLEY/SOUTHERN APPALACHIANS...   ...SUMMARY...   AN OUTBREAK OF SEVERE STORMS INCLUDING STRONG TORNADOES AND   WIDESPREAD DAMAGING WINDS APPEARS LIKELY MONDAY AND MONDAY NIGHT   ACROSS PARTS OF THE LOWER MISSISSIPPI VALLEY AND TENNESSEE VALLEY.   ...SYNOPSIS...   AN EXTENSIVE CLOSED LOW/PARENT LONGWAVE TROUGH OVER THE CENTRAL   CONUS WILL SHIFT SLOWLY EASTWARD ON MONDAY...WHILE ONE OR MORE   DISTURBANCES/HIGHER-LEVEL SPEED MAXIMA EJECT EAST-NORTHEASTWARD   THROUGH THE BASE OF THE TROUGH TOWARD THE OZARKS AND LOWER/MIDDLE MS   RIVER VALLEY. THE PRIMARY SURFACE CYCLONE WILL MOVE SLOWLY ACROSS   THE MIDDLE MO RIVER VALLEY...WITH A WARM FRONT EXTENDING   EAST-SOUTHEASTWARD ACROSS THE NEIGHBORING MIDWEST. A COMPOSITE   DRYLINE/PACIFIC COLD FRONT WILL SLOWLY SPREAD EAST-SOUTHEASTWARD   ACROSS PARTS OF THE LOWER MO VALLEY/OZARKS AND SOUTHEAST TX/TX GULF   COAST.   ...TN VALLEY/CENTRAL GULF COAST STATES/ARKLAMISS...   INITIALLY...IT SEEMS LIKELY THAT CLUSTERS OF TSTMS WILL BE ONGOING   ACROSS THE REGION MONDAY MORNING...PARTICULARLY NEAR/EAST OF THE MS   RIVER INTO PARTS OF THE OH/TN RIVER VALLEYS. SOME OF THESE STORMS   MAY BE SURFACE-BASED OR NEARLY SO AND CAPABLE OF AN EARLY DAY SEVERE   THREAT. FROM THE DAY 2 PERSPECTIVE...IT SEEMS VIABLE THAT THIS   CONVECTION MAY INFLUENCE /VIA OUTFLOW AND DIFFERENTIAL HEATING/ THE   NORTHWARD EXTENT OF THE PEAK SEVERE RISK SUBSEQUENTLY MONDAY   AFTERNOON INTO MONDAY NIGHT.   MEANWHILE...AN INCREASINGLY BROAD/EAST-NORTHEASTWARD SHIFTING PLUME   OF 60S F SURFACE DEWPOINTS WILL RESIDE ACROSS THE MAJORITY OF THE   REGION VIA THE DIURNAL MAINTENANCE OF MODERATELY STRONG   SOUTHWESTERLY LOW-LEVEL WINDS. AMPLE HEATING IN   CONVECTIVE/OUTFLOW-FREE AREAS WILL LIKELY LEAD TO MODERATE BUOYANCY   /1500-2500 J PER KG MLCAPE/ WITHIN AN INCREASING INHIBITION-FREE   WARM SECTOR BY AFTERNOON/EARLY EVENING. ESPECIALLY GIVEN CURRENT   EXPECTATIONS OF EARLY DAY CONVECTION/POTENTIAL OUTFLOW...SUCH   DESTABILIZATION APPEARS MOST PROBABLE WITHIN A CORRIDOR FROM THE   SABINE RIVER VICINITY OF TX/LA NORTHEASTWARD ACROSS MS INTO   NEIGHBORING AL/TN.   AS THE AIR MASS DESTABILIZES...STORMS SHOULD DEVELOP/REINVIGORATE   PARTICULARLY WITHIN A CORRIDOR OF AMPLE/MOIST LOW-LEVEL CONFLUENCE   ACROSS NORTHERN/CENTRAL MS AND LA INTO WESTERN/MIDDLE TN AND   WESTERN/NORTHERN AL. THIS COULD BE AS EARLY AS AFTERNOON...BUT   ESPECIALLY INTO THE EVENING HOURS AS AN EMBEDDED IMPULSE/SPEED MAX   WITHIN THE BASE OF THE LONGWAVE TROUGH BEGINS TO APPROACH/OVERSPREAD   THE REGION.   HIGHLIGHTED BY A 75-100 KT SOUTHWESTERLY MID-LEVEL SPEED MAX...BOTH   DEEP LAYER/LOW-LEVEL SHEAR WILL BE QUITE STRONG ACROSS THE REGION   WITH EFFECTIVE BULK SHEAR OF 50+ KT. SCENARIO SHOULD YIELD AN   EXPANDING/INTENSIFYING CORRIDOR OF STORMS...AGAIN PARTICULARLY BY   MONDAY EVENING...WHICH WOULD LIKELY INCLUDE A MULTI-MODAL SCENARIO   OF SEMI-DISCRETE SUPERCELLS AND A NOCTURNAL TREND TOWARD   HIGHLY-ORGANIZED QUASI-LINER BANDS WITH BOWS/LEWP STRUCTURES. SEVERE   HAIL ASIDE /AFTERNOON THROUGH EARLY EVENING/...TORNADOES...INCLUDING   A VIABLE POTENTIAL FOR STRONG TORNADOES...CAN BE EXPECTED ALONG WITH   THE POSSIBILITY OF WIDESPREAD DAMAGING WINDS THROUGH THE   EVENING/OVERNIGHT HOURS AS STORMS DEVELOP EAST/NORTHEASTWARD   ESPECIALLY ACROSS MS/AL/TN.   ...MIDWEST...   NEAR/SOUTH OF A WARM FRONT ACROSS THE REGION...THE AIR MASS SHOULD   STEADILY DESTABILIZE MONDAY AFTERNOON IN THE WAKE OF EARLY DAY   ELEVATED CONVECTION/CLOUD COVER. LOWER TOPPED STRONG/SEVERE TSTMS   WILL BE POSSIBLE MONDAY AFTERNOON/EARLY EVENING...POTENTIALLY AS FAR   WEST-NORTHWEST AS IA IN VICINITY OF THE SURFACE LOW/NARROWING WARM   SECTOR. SEVERE HAIL AND SOME TORNADOES WILL BE POSSIBLE ACROSS THE   REGION...MAINLY PRIOR TO THE MID-EVENING HOURS.   ..GUYER.. 04/27/2014

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Not upgrading to a high risk is quite weird there considering all of the parameters coming together in AR.  That outlook was weirdly written too... Eastern Western Kansas?  How about West Central Kansas?  

 

There was more attention paid to the areas that were outside the highest risk locations, to be honest.

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Not upgrading to a high risk is quite weird there considering all of the parameters coming together in AR.  That outlook was weirdly written too... Eastern Western Kansas?  How about West Central Kansas?  

 

Has there ever been 3 straight days of Moderate Risk from the SPC before?

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Has there ever been 3 straight days of Moderate Risk from the SPC before?

 

The D1, D2 and D3 risks on 4/25/11.

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Since this is the first significant outbreak of this season a reminder is necessary of usual procedures.  When things get fast and furious it is helpful to post only confirmed tor warnings, radars, screen captures, significant damage, etc. instead of every svr warning.  I personally appreciate radars since I'm pretty much limited to NWS radars myself.  I have a strong feeling that we may be overwhelmed starting later today as the line upzips from Omaha to the Arklatex.

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Wednesday is also looking rather volatile on the EC this run of the Euro, just another thing to look at.

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I'm more than a bit confused about what to expect today after reading Springfield, MO's morning AFD. Also looking at various model solutions and reading the latest SPC Mesoscale discussion has left me even more confused about when convection will fire and how many 'rounds' there will be and the impacts expected. 

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First 2 severe thunder storm watches of this outbreak have been posted for parts of Oklahoma and Kansas

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I'm more than a bit confused about what to expect today after reading Springfield, MO's morning AFD. Also looking at various model solutions and reading the latest SPC Mesoscale discussion has left me even more confused about when convection will fire and how many 'rounds' there will be and the impacts expected.

I agree. I am wondering now if the SPC aligns with their thinking in the 8AM outlook. SGF is certainly downplaying any TOR possibilities.

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That spc disco used a lot of words like unclear and not certain. Anyway Tulsa cut the severe warned percentages in W. Ar from the 60-70 range almost in half on the decision support page. It will be interesting to see the next Day 1 Outlook.

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First post.. I really think a high risk area for central and northern Arkansas and southern Missouri was justified. I guess we will see just how things turn out later. We already got some severe cells firing up in Oklahoma and Kansas.

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That spc disco used a lot of words like unclear and not certain. Anyway Tulsa cut the severe warned percentages in W. Ar from the 60-70 range almost in half on the decision support page. It will be interesting to see the next Day 1 Outlook.

Sent from my XT1060

 

I see 60's in NW Arkansas and even a 47 up near Miami, OK as of 6:19 AM? That's higher than the last update I saw. Also tornado is "28" where you are at I believe, which is the highest on the page?

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First post.. I really think a high risk area for central and northern Arkansas and southern Missouri was justified. I guess we will see just how things turn out later. We already got some severe cells firing up in Oklahoma and Kansas.

Not great timing for the OKC Memorial Marathon this morning.

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I see 60's in NW Arkansas and even a 47 up near Miami, OK as of 6:19 AM? That's higher than the last update I saw. Also tornado is "28" where you are at I believe, which is the highest on the page?

 

You are right that is what the page says now.  Maybe I should not post any information till I am fully awake, lol.   

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Need to continue to pay close attention to central OK tonight / tomorrow morning. RAP and SPC wrf blow up a nice line ahead of the DL as strong upper level forcing moves in, with still 2000J/kg of CAPE in place, and a heck of a lot of low level shear

 

RAP and SPC WRF nailed this morning.

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RAP and SPC WRF nailed this morning.

 

Yeah, I was about to make a comment that the SPC WRF seems to have nailed the situation unfolding now how it expected. Also the Euro wasn't too bad as well. 

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Not great timing for the OKC Memorial Marathon this morning.

KFOR is reporting the run has been delayed until 7:15 local. Wouldn't be surprised if it is delayed some more given the severe weather.

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KFOR is reporting the run has been delayed until 7:15 local. Wouldn't be surprised if it is delayed some more given the severe weather.

 

It should be... there are plenty of storms behind that. Not sure why it wasn't delayed more unless it is typical to do this in short increments.

 

Pulsing ZDR arc implying at least weak updraft helicity on the southern storm entering the metro with very brief TVSs reported over the past hour. Fun times this morning. 

 

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It should be... there are plenty of storms behind that. Not sure why it wasn't delayed more unless it is typical to do this in short increments.

 

I know that http://perryweather.com/ is providing some support for the marathon, but it seems to me that marathon officials are not getting (good/any) information from him regarding the storms, because if so, they would have delayed the race until at least 8.

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I know that http://perryweather.com/ is providing some support for the marathon, but it seems to me that marathon officials are not getting (good/any) information from him regarding the storms, because if so, they would have delayed the race until at least 8.

 

655am-Downtown OKC will be most affected by strong/severe storms 715-745 am with half dollar hail/60 mph gusts possible.

 

The Significant Weather Advisory for OKC is urging those attending the marathon to take shelter for imminent dangerous weather conditions. Hope that is being heeded! 

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62MPH gust at both the Yukon, OK ASOS and the Piedmont, OK Mesonet site. 

 

KRCE 271155Z AUTO 22008G54KT 030V030 3/4SM +TSRA BKN002 17/16 A2951 RMK AO2 P0060

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NWS Norman@NWSNorman[/size] 8m

655am-Downtown OKC will be most affected by strong/severe storms 715-745 am with half dollar hail/60 mph gusts possible.

The Significant Weather Advisory for OKC is urging those attending the marathon to take shelter for imminent dangerous weather conditions. Hope that is being heeded!

Marathon has now been delayed until 8am local, as it should be!

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655am-Downtown OKC will be most affected by strong/severe storms 715-745 am with half dollar hail/60 mph gusts possible.

 

The Significant Weather Advisory for OKC is urging those attending the marathon to take shelter for imminent dangerous weather conditions. Hope that is being heeded! 

 

 

It is hard to get thousands of people into sheltered areas around there, but the marathon is now delayed until 8 (https://www.facebook.com/OKCMarathon).

 

I have to wonder what sort of actual support is being provided to the marathon by Perry Weather, and if anything will change in future years.  I remember when the partnership was announced a year or two ago, the NWS in Norman was wondering why they'd outsource to some recent college graduate in Northern Texas when they had much better options in the Norman area.

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Sorry for going slightly off-topic, but why does the SPC's thunderstorm outlook not correspond with NWS forecasts? As an example, the most recent SPC TO has Topeka at a 10% chance to see thunder all day, meanwhile my NWS forecast says 70% chance. Is it because the NWS forecast is for precipitation in general? Thanks in advance, guys.

 

Vastly different things are being forecast here. The NWS WFO is forecasting probability of precipitation (at least 0.01") across either that time period or the areal coverage. The SPC is forecasting a 10% chance of a tornado within 25 miles of any given point.

 

The SPC forecasts are based on the average daily probabilities of a tornado occurring within 25 miles of a point. I don't know the exact numbers for the TOP area off the top of my head, but let's say any given day is a 0.5% chance of a tornado occurring within 25 miles. The 10% forecast today is saying that today the risk is 20 times greater than the average day. 10% is a small number, but in this case is actually a hugely elevated risk.

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Vastly different things are being forecast here. The NWS WFO is forecasting probability of precipitation (at least 0.01") across either that time period or the areal coverage. The SPC is forecasting a 10% chance of a tornado within 25 miles of any given point. Is that what you were referring to as well?

The SPC forecasts are based on the average daily probabilities of a tornado occurring within 25 miles of a point. I don't know the exact numbers for the TOP area off the top of my head, but let's say any given day is a 0.5% chance of a tornado occurring within 25 miles. The 10% forecast today is saying that today the risk is 20 times greater than the average day. 10% is a small number, but in this case is actually a hugely elevated risk.

Thanks for the response. To clarify, I'm talking about the enhanced thunderstorm outlook as opposed to the convective outlook product.

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Crapvection. Crapvection everywhere, and it's only 12z. Not elevated showers that will die out, but intense surface-based storms with 50 kft tops. To anyone who wondered why they didn't go HIGH last night for the initial SWODY1, I think you have your answer. Today will still be dangerous and there will still be tornadoes, probably quite a few, but the highly-organized threat over a wide latitudinal expanse is in trouble IMHO.

 

Just to clarify, the open warm sector threat over AR/LA and perhaps E OK/NE TX is still robust, and that probably had the highest ceiling all along. It's just that the dryline itself convected in earnest far too early to maximize the threat with that mode.

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Thanks for the response. To clarify, I'm talking about the enhanced thunderstorm outlook as opposed to the convenctive outlook product.

 

I see, the idea works similarly though. The SPC product is saying thunder should happen 1 out of every 10 times they forecast it, whereas the NWS WFO is saying there is a 70% chance of 0.01" rain, not necessarily a 70% chance of thunder.

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   CONCERNING...SEVERE THUNDERSTORM WATCH 92...93...

   VALID 271255Z - 271430Z

   THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH
   92...93...CONTINUES.

   SUMMARY...SEVERE WEATHER THREAT WILL CONTINUE ACROSS WW 92 AND 93
   WITH AN ADDITIONAL THREAT OF HAIL AND DAMAGING WINDS S OF WW 93 IN N
   TX. TSTMS WILL BECOME INCREASINGLY SURFACE-BASED WITH EWD
   PROGRESSION...INCREASING THE THREAT OF BOTH DAMAGING WINDS AND
   TORNADOES.

   DISCUSSION...TSTM ACTIVITY WITHIN THE TWO WATCHES APPEARS TO BE PART
   OF TWO SEPARATE REGIMES.

   ACTIVITY WITHIN WW 92 IS LIKELY TIED TO INCREASED ASCENT ASSOCIATED
   WITH A LEAD SHORTWAVE AND ITS ASSOCIATED SPEED MAX. THIS ACTIVITY
   WAS INITIALLY ELEVATED /CONFIRMED BY 12Z TOP SOUNDING/ AND WILL
   LIKELY CONTINUE TO BE OVER THE NEXT SEVERAL HOURS AS IT PROGRESSES
   NEWD. AS A RESULT...THE MAIN THREAT REMAINS SEVERE HAIL. ANY
   SURFACE-BASED ACTIVITY WILL LIKELY BE DELAYED UNTIL THIS AFTERNOON
   WHEN THE COLD FRONT MOVES THROUGH.

   MOST OF THE TSTMS IN WW 93 APPEAR TO BE SURFACE /OR AT LEAST
   NEAR-SURFACE/ ORIENTATED AS A MORE EWD MOTION HAS BEEN OBSERVED WITH
   RECENT RADAR IMAGERY. SEVERE GUSTS HAVE ALSO ALREADY BEEN REPORTED.
   THIS ACTIVITY INITIATED ALONG THE COLD FRONT BUT HAS NOW DECOUPLED
   FROM IT AND MOVED INTO THE WARM SECTOR. WARM SECTOR ACROSS ERN OK
   MAY STILL BE A BIT HOSTILE TOWARDS SURFACE-BASED CONVECTION BUT THAT
   SHOULD CHANGE QUICKLY AS MOISTURE CONTINUES TO ADVECT NWD AND LARGE
   SCALE LIFT PERSISTS OVER THE AREA. AS A RESULT...THE SVR RISK WILL
   CONTINUE WITH AN INCREASING THREAT FOR A FEW TORNADOES.

   FARTHER S...SURFACE-BASED TSTMS HAVE DEVELOPED ALONG THE FRONT
   ACROSS NW TX WITH ELEVATED TSTMS AHEAD OF THIS ACROSS N TX. SOME
   ISOLATED HAIL IS POSSIBLE WITH THE ELEVATED CONVECTION WITH HAIL AND
   DAMAGING WINDS POSSIBLE WITH THE SURFACE-BASED STORMS FARTHER W.

 

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