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Virtual Chase Thread 2012


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Posted
  • Location: on a canal , probably near Northampton...
  • Weather Preferences: extremes n snow
  • Location: on a canal , probably near Northampton...

mark hills signal has been dropping off all evening, joemiller on chaser is watching some interesting low clouds..

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Posted
  • Location: Caterham-on-the-hill, Surrey, 190m asl (home), Heathrow (work)
  • Location: Caterham-on-the-hill, Surrey, 190m asl (home), Heathrow (work)

SPC have a MODERATE RISK for Saturday aross OK and KS, not suprising given the 00z NAM CAPE, 0-3km SR helicity charts and strong 500mb westerly jet arriving! Hallmarks of a major tornado outbreak I think.

http://www.spc.noaa.gov/products/outlook/day3otlk.html

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Posted
  • Location: on a canal , probably near Northampton...
  • Weather Preferences: extremes n snow
  • Location: on a canal , probably near Northampton...
Today and tommorow are just leading us into Saturdays major event. I would think we shall see record numbers of Chaser live streams this Saturday.
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Posted
  • Location: Scarborough, North Yorkshire - 80m ASL
  • Weather Preferences: Tornadoey
  • Location: Scarborough, North Yorkshire - 80m ASL

It certainly does have all the hallmarks of a big event. The day 3 moderate has historically been somewhat of a curse on events... although that was well and truly broken with the day 3 moderate issued on April 25th last year. I remember the 3 day moderate back in 2009 which ended up being a mainly wind event though (with Kirksville being the only notable tornado) and that looked pretty good 3 days out. Given there are a number of large communities right in the firing line, I wouldn't be too upset to see this underperform... Wichita and OKC will both be in the firing line.

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Posted
  • Location: Hatfield, Doncaster, South Yorkshire
  • Location: Hatfield, Doncaster, South Yorkshire

Reading some of the TVN forecasts earlier, and the inherent belief is that Northern TX, OK and a fair bit of KS will be getting it this weekend.

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Posted
  • Location: Scarborough, North Yorkshire - 80m ASL
  • Weather Preferences: Tornadoey
  • Location: Scarborough, North Yorkshire - 80m ASL

Eastern Nebraska and much of Iowa should be under the gun too. Seems like a potent warm front setup in addition storms firing off the dryline.

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Posted
  • Location: Evesham/ Tewkesbury
  • Weather Preferences: Enjoy the weather, you can't take it with you 😎
  • Location: Evesham/ Tewkesbury

Looks like Spc are quite concerned about Saturdays/Early Sundays storms. Quite a big area under the MDT risk including Oklahoma City. Looks like these storms could well rumble on to the Early Hours of Sunday Morning....

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Posted
  • Location: Caterham-on-the-hill, Surrey, 190m asl (home), Heathrow (work)
  • Location: Caterham-on-the-hill, Surrey, 190m asl (home), Heathrow (work)

Saturday is looking to be a significant severe weather day across the southern/central Plains with probable strong tornado outbreak, SPC have gone HIGH RISK with 60% probabilities and some very strong language such as 'High-End Life Threatening Event' -

post-1052-0-20295100-1334301863_thumb.gipost-1052-0-47932200-1334301872_thumb.gi

...SRN AND CNTRL PLAINS...

AN IMPRESSIVE UPPER-LEVEL LOW WILL MOVE EWD ACROSS FOUR CORNERS

REGION SATURDAY AS A POWERFUL 90 TO 110 KT MID-LEVEL JET EJECTS NEWD

INTO THE SRN AND CNTRL PLAINS. AHEAD OF THE SYSTEM...A CORRIDOR OF

MODERATE TO STRONG INSTABILITY IS FORECAST ACROSS ECNTRL KS...CNTRL

OK INTO NW TX. THIS COMBINED WITH STEEP MID-LEVEL LAPSE RATES AND

STRONG LOW-LEVEL SHEAR WILL BE VERY FAVORABLE FOR SEVERE STORMS AND

A TORNADO OUTBREAK WILL BE LIKELY ACROSS THE SRN AND CNTRL PLAINS

FROM LATE SATURDAY AFTERNOON LASTING THROUGH THE EVENING AND INTO

THE OVERNIGHT PERIOD.

NAM AND NAMKF FORECAST SOUNDINGS AT 00Z SATURDAY EVENING FROM SALINA

KS SWD TO AROUND OKLAHOMA CITY SHOW MLCAPE VALUES FROM 2000 TO 3000

J/KG WITH 0-6 KM SHEAR IN THE 60 TO 75 KT RANGE. IN

ADDITION...HODOGRAPHS ARE LARGE AND LOOPED WITH 0-1 KM SHEAR VALUES

IN THE 30 TO 40 KT RANGE. THIS ENVIRONMENT SHOULD BE VERY FAVORABLE

FOR SUPERCELLS AND TORNADOES. 0-3 KM STORM RELATIVE HELICITIES ARE

FORECAST TO BE AROUND 400 M2/S2 WHICH IS IDEAL FOR STRONG TORNADOES

AND A TORNADO OUTBREAK APPEARS LIKELY. THE GREATEST THREAT FOR

SIGNIFICANT TORNADOES SHOULD EXIST SATURDAY EVENING FROM SALINA SWD

TO OKLAHOMA CITY. 700 TO 500 MB LAPSE RATES AROUND 7.5 C/KM WILL

ALSO BE FAVORABLE FOR LARGE HAIL AND HAIL GREATER THAN 2 INCHES WILL

BE POSSIBLE THE MORE INTENSE SUPERCELLS. A WIND DAMAGE THREAT WILL

ALSO EXIST DUE TO THE EXPECTED INTENSE NATURE OF THE STORMS.

THE MAIN CONCERN FOR THIS FORECAST IS CONVECTIVE COVERAGE. MANY OF

THE MODELS DO NOT DEVELOP NUMEROUS THUNDERSTORMS ALONG THE DRYLINE.

IN SPITE OF THIS...THE MODELS DIMINISH THE CAP ACROSS THE SRN AND

CNTRL PLAINS LATE SATURDAY AFTERNOON SO THIS BRINGS THE MODELS INTO

QUESTION. IN ADDITION...THE MODELS DRIVE A BAND OF LARGE-SCALE

ASCENT ACROSS CNTRL KS DURING THE EARLY EVENING SUGGESTING MANY

STORMS SHOULD INITIATE WITH STORMS INITIATING SWD WITH TIME EARLY

SATURDAY EVENING AS THE LOW-LEVEL JET STRENGTHENS. THESE FACTORS

COMBINED WITH SFC DEWPOINTS IN THE LOWER TO MID 60S F AND VERY

FAVORABLE LOW-LEVEL SHEAR PROFILES SHOULD PRODUCE AND ENVIRONMENT

FAVORABLE FOR A TORNADO OUTBREAK. AFTER COLLABORATION WITH WFOS

WICHITA...NORMAN...TOPEKA...TULSA AND DODGE CITY...A HIGH RISK WILL

BE ISSUED DUE TO THE POTENTIAL FOR A HIGH-END LIFE THREATENING EVENT

ACROSS THE SRN AND CNTRL PLAINS.

I hope Paul, Arron and James play safe ... going to be very dangerous tomorrow!

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Posted
  • Location: Scarborough, North Yorkshire - 80m ASL
  • Weather Preferences: Tornadoey
  • Location: Scarborough, North Yorkshire - 80m ASL

I don't ever recall seeing a day 2 High risk issued in the morning. They are rare enough in the afternoon of Day 2! A little surprised they have so much confidence given they don't seem overly confident about today still and a lot about tomorrow will depend on what happens this evening, but it's obviously pretty clear there is going to be widespread storms at least after dark. By 0z, the NAM precip chart is still only showing a small blip north of Wichita on the Dryline (although this is superimposed of a small area of backing winds) with discrete cells firing towards dusk down in OK. Given a few boundaries from this evenings predicted storms which won't be modelled, I'd expect initiation to be less of an issue during daylight hours as the models make out, however.

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Posted
  • Location: Wickham, S Hampshire, UK
  • Location: Wickham, S Hampshire, UK

I shall be tracking this one, especially as it's a Saturday night. The location of initiation will be a tricky one with a rather complex collection of potential boundaries in place over the region, more especially OFBs from early morning clutter.

The overall parameters however are pretty much top-drawer for a high-end event and actually are not far off (at the 2 day out range at least) those from the 27th April outbreak in AL/MS last year. Not surprised a few UK based chasers have elected to scoot over for this one.

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Posted
  • Location: Torrington, Devon
  • Weather Preferences: storms - of the severe kind
  • Location: Torrington, Devon

Ominous reading looking at that text from SPC for Saturday.

Will be tracking this one.

Have a good one guys

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My virtual target would start at Salina in Kansas, so I could keep the Nebraska option open at the start of the day. My instincts say go to Nebraska where the surface low is and better chance of low level directional shear.

Edited by nzstorm
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Posted
  • Location: Hatfield, Doncaster, South Yorkshire
  • Location: Hatfield, Doncaster, South Yorkshire

Norman/Moore OK getting hammered by large hail at the moment.

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  • 2 weeks later...
Posted
  • Location: Headcorn, Kent, UK
  • Weather Preferences: Severe Weather, Thunderstorms
  • Location: Headcorn, Kent, UK

post-9700-0-15207300-1335523339_thumb.gi post-9700-0-21397800-1335523346_thumb.gi

DAY 1 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

1236 AM CDT FRI APR 27 2012

VALID 271200Z - 281200Z

...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS CENTRAL PLAINS TO

MO...

...SYNOPSIS...

PROGRESSIVE UPPER-AIR PATTERN FCST THROUGH PERIOD...FEATURING TWO

PRINCIPAL SHORTWAVE TROUGHS NOW OVER WRN CONUS...

1. HIGH-AMPLITUDE TROUGH NOW EVIDENT IN MOISTURE CHANNEL IMAGERY

FROM NRN NV NWWD ACROSS COASTAL BC. EMBEDDED VORTICITY MAXIMA ARE

EXPECTED TO PHASE TOGETHER IN SUPPORT OF CLOSED 500-MB CYCLONE

DEVELOPMENT DURING AFTERNOON...OVER NRN ROCKIES. CYCLONE CENTER

SHOULD REACH SERN MT/NERN WY/WRN SD BORDER REGION BY END OF PERIOD.

MEANWHILE...

2. COMPACT SHORTWAVE TROUGH -- INITIALLY OVER NRN NM/ERN CO BORDER

-- SHOULD MOVE ENEWD ACROSS CENTRAL HIGH PLAINS...REACHING ERN

PORTIONS KS/NEB BORDER REGION BY 28/00Z. THIS FEATURE WILL

DEAMPLIFY SUBSTANTIALLY FROM ABOUT 27/21Z ONWARD...REACHING NRN/ERN

IA AS WEAK VORTICITY LOBE BY END OF PERIOD.

MEANWHILE...STG MID-UPPER LEVEL SHORTWAVE TROUGH -- NOW MOVING SEWD

ACROSS INTERIOR MID-ATLANTIC REGION -- IS EXPECTED TO PIVOT EWD OVER

NEW ENGLAND EARLY IN PERIOD. ASSOCIATED SFC CYCLOGENESIS WILL

AFFECT CANADIAN MARITIMES. TRAILING COLD FRONT WILL DECELERATE

THROUGH AFTERNOON THEN BECOME QUASISTATIONARY OVER CAROLINAS. WRN

LIMB OF BAROCLINIC ZONE WILL MOVE NWD ACROSS SRN PLAINS AND

AR...LOCATED OVER OZARKS AND ERN KS AND CONNECTING TO SFC LOW OVER

E-CENTRAL KS BY 28/00Z. OCCLUDED FRONT WILL EXTEND NWWD FROM LOW

ACROSS NEB/SD TO SFC CYCLONE OVER ERN MT...PRECEDING NRN-STREAM

PERTURBATION. COLD FRONT TRAILING KS LOW WILL EXTEND WSWWD TO NWRN

OK AND NRN TX PANHANDLE BY 28/00Z...WITH DRYLINE EXTENDING SWD TO

N-CENTRAL/NERN OK THEN SSWWD OVER CENTRAL TX. LOW SHOULD MOVE NEWD

ACROSS NRN MO AND WEAKEN OVERNIGHT...WITH COLD FRONT SWWD ACROSS

CENTRAL OK AND NW TX BY 28/12Z.

...CENTRAL PLAINS TO MO...

--- EARLY ---

SCATTERED TSTMS MAY BE ONGOING AT START OF PERIOD...IN PLUME FROM

NEB PANHANDLE AND NERN CO SSEWD ACROSS PORTIONS WRN KS. THIS WILL

REPRESENT NEWD SHIFT OF STG DEEP-LAYER ASCENT PLUME AND ACCOMPANYING

CONVECTIVE REGIME NOW COVERING MUCH OF ERN CO AND EXTENDING INTO WRN

OK PANHANDLE. SVR THREAT BY START OF PERIOD TIME WILL BE MRGL AT

BEST...GIVEN WEAK NEAR-SFC THETAE EXPECTED OVER SWRN NEB AND WRN KS.

ISOLATED HAIL/GUSTS NEAR SVR LEVELS CANNOT BE RULED OUT. THIS

ACTIVITY WILL MOVE NEWD OVER NEB AND WEAKEN BY MIDDAY.

--- AFTERNOON/EVENING ---

RELATIVELY COMPACT CORRIDOR OF SUPERCELL/TORNADO POTENTIAL MAY

DEVELOP AND SHIFT EWD TODAY ACROSS MAINLY KS. LARGE/DAMAGING HAIL

ALSO IS POSSIBLE. SOME UNCERTAINTIES REMAIN REGARDING

TIMING/DURATION OF FAVORABLE SFC HEATING/DESTABILIZATION OVER

PORTIONS CENTRAL-ERN KS...OTHERWISE NARROW CORRIDOR OF EVEN GREATER

SVR PROBABILITIES MAY BECOME APPARENT.

BY EARLY AFTERNOON...CORRIDOR OF FAVORABLE DESTABILIZATION IS

POSSIBLE BEHIND MORNING ACTIVITY AND AHEAD OF SURGING DRYLINE. MOST

PROBABLE LOCATION ATTM APPEARS TO BE ACROSS PORTIONS WRN/CENTRAL

KS...IN ARC FROM N THROUGH ESE OF NEARBY SFC LOW. MODIFIED

RUC/ETA-KF FCST SOUNDINGS SUGGEST MID-UPPER 60S F SFC

TEMPS...CERTAINLY ATTAINABLE WITH EVEN BRIEF SLOT OF PRE-DRYLINE SFC

INSOLATION...WILL BE SUFFICIENT TO YIELD SFC-BASED EFFECTIVE INFLOW

PARCELS AND MLCAPE 500-1500 J/KG. STG VEERING OF WINDS WITH HEIGHT

AND LOW-LEVEL SPEED SHEAR...COMBINED WITH LOW-LEVEL VORTICITY INVOF

SFC LOW AND NEARBY WARM FRONTAL ZONE...SUPPORT RISK FOR SUPERCELLS

WITH LARGE HAIL AND TORNADOES.

EWD-SHIFTING WARM SECTOR SLOT WILL WIDEN AND BECOME MORE BUOYANT

WITH TIME AND EWD EXTENT ACROSS KS DURING MID-LATE AFTERNOON. ARC

OF SVR TSTMS SHOULD DEVELOP....WHETHER SEPARATELY FROM EARLIER

ACTIVITY FARTHER W OR AS SEWD-BUILDING EXTENSION. ACTIVITY

EVENTUALLY MAY MERGE INTO SVR WIND-PRODUCING AND NEARLY CONTINUOUS

ARC. HOWEVER...FOR MUCH OF AFTERNOON INTO EARLY EVENING...PRESENCE

OF SIGNIFICANT ORTHOGONAL COMPONENT OF FLOW ALOFT SUGGESTS DISCRETE

SUPERCELLS WILL REMAIN OVER ERN KS INTO THAT PART OF SWRN MO ALONG

AND SW OF WARM FRONT. PRECONVECTIVE MLCAPE MAY REACH 2500 J/KG IN

E-CENTRAL/SERN KS...WITH 0-1 KM SRH 200-300 J/KG AND EFFECTIVE SHEAR

MAGNITUDES NEAR 50 KT.

EXTENSION OF THREAT INTO N-CENTRAL/NERN OK IS CONDITIONAL DUE TO

SUBSTANTIALLY STRENGTHENED CAPPING LIKELY OVER OK...ALONG WITH

WEAKER LOW-LEVEL CONVERGENCE. SVR PROBABILITIES THEREFORE DIMINISH

WITH SWD EXTENT OVER OK. SVR POTENTIAL SHOULD DIMINISH WITH EWD

EXTENT OVERNIGHT ACROSS S-CENTRAL MO TO MS RIVER AREA.

...SERN CONUS...

SCATTERED TSTMS ARE EXPECTED TO DEVELOP INVOF SFC FRONTAL

ZONE...FROM ERN SC AT LEAST AS FAR WNWWD AS NERN AL...BECOMING

WIDELY SCATTERED TO ISOLATED FARTHER NW WHERE LOW-LEVEL FRONTAL

FORCING WILL BE WEAK. SFC DEW POINTS 60S F...STG HEATING...AND

FRONTAL LIFT WILL BE SUFFICIENT TO REMOVE MLCINH AMIDST 1000-2000

J/KG MLCAPE. LOW-LEVEL FLOW AND SHEAR WILL BE WEAK...BENEATH

GENERALLY 25-35 KT EFFECTIVE SHEAR MAGNITUDE. PRIMARY MODE SHOULD

BE MULTICELLULAR...WITH SPORADIC STG-SVR DOWNDRAFTS AND HAIL

POSSIBLE. CONVECTIVE COVERAGE AND SVR POTENTIAL SHOULD DIMINISH

MARKEDLY AFTER 00Z...DUE TO STABILIZING EFFECTS OF BOTH SFC DIABATIC

COOLING AND CONVECTIVE OUTFLOWS.

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Posted
  • Location: on a canal , probably near Northampton...
  • Weather Preferences: extremes n snow
  • Location: on a canal , probably near Northampton...

Oh, they have weather in the US of A too...........

I have been that into the weather over here, I forgot to keep checking the StormChasing potential over there..

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Posted
  • Location: South Shields Tyne & Wear half mile from the coast.
  • Location: South Shields Tyne & Wear half mile from the coast.

An upgrade to moderate risk for parts of central eastern Kansas into western Missouri.

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MESOSCALE DISCUSSION 0602

NWS STORM PREDICTION CENTER NORMAN OK

0616 AM CDT FRI APR 27 2012

AREAS AFFECTED...PARTS OF CNTRL-ERN KS AND FAR WRN MO

CONCERNING...OUTLOOK UPGRADE

VALID 271116Z - 271215Z

THERE WILL BE A CATEGORICAL UPGRADE FROM A SLIGHT TO MODERATE RISK

OVER CNTRL-ERN KS AND FAR WRN MO FOR THE UPCOMING 1300Z DAY 1

CONVECTIVE OUTLOOK. CONFIDENCE HAS INCREASED REGARDING A GREATER

THREAT FOR SUPERCELLS POTENTIALLY CAPABLE OF A FEW STRONG TORNADOES

AND LARGE DESTRUCTIVE HAIL ACROSS THE MODERATE RISK AREA.

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Posted
  • Location: Leigh On Sea - Essex & Tornado Alley
  • Location: Leigh On Sea - Essex & Tornado Alley

Not surprised by that at all Paul.

Today looks very good, especially near the triple point east of Wichita later.

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Posted
  • Location: Caterham-on-the-hill, Surrey, 190m asl (home), Heathrow (work)
  • Location: Caterham-on-the-hill, Surrey, 190m asl (home), Heathrow (work)

Crept in quietly this risk for strong tornadoes today across Ern Kansas.

Strong 0-3km shear across E and NE Kansas, just ahead of cyclone moving NE across south central and eastern KS later and strong 500mb jet aloft

post-1052-0-46172500-1335532972_thumb.gipost-1052-0-13180800-1335533088_thumb.gi

low's warm sector will have the CAPE across eastern KS at 00z (18z CDT),

post-1052-0-98493900-1335533153_thumb.gi

... so quite fancy storms that fire along warm front lifting ahead of the low - as this is where shear will likely be greatest and thus risk of nadoes. Going to target the stretch of I-35 between El Dorado and Emporia.

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Posted
  • Location: Leigh On Sea - Essex & Tornado Alley
  • Location: Leigh On Sea - Essex & Tornado Alley

These High Shear & Low Cape Days usually go bang in quite a spectacular way (See Henrysville Indiana March 2nd Outbreak)

If clearing can occur near the Warm Front which should be around the Emporia area by 00z - 03z then 1 or 2 Dominant Supercells could become LongTracked Cyclic Tornado Producers riding along the boundary.

I don't know why but I also love the area further South of Wichita and can also see a Tornado Machine march across South Central Kansas as well from Medicine Lodge to Coffeyville later on.

This could be the last decent Moderate Risk for quite some time as well so I would expect numerous Chasers to be out on this.

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