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user700

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    The North Of England Regional Discussion

    in Regional

    Posted · Edited by danieluk

    I live on the side of Billinge Hill mate so luckily flooding is not an issue here. I can only imagine what parts of Wigan look like now and its still raining! In fact its raining heavier tonight than it has throughout the past 48 hours, incredible stuff!

    I live near Wigan I recorded 46 mm of rain yesterday and 39 mm so far today

    Virtual Chase Thread 2012

    in Storm Chase USA

    Posted

    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.

    Severe Outbreak - This Weekend - Discussion

    in Storm Chase USA

    Posted

    day1otlk_1200.gif

    Categorical Day1 1200Z Outlook

    Forecast Discussion

    SPC AC 140543

    DAY 1 CONVECTIVE OUTLOOK

    NWS STORM PREDICTION CENTER NORMAN OK

    1243 AM CDT SAT APR 14 2012

    VALID 141200Z - 151200Z

    ...THERE IS A HIGH RISK OF SVR TSTMS TODAY ACROSS MUCH OF CENTRAL

    AND EASTERN NEBRASKA AND PARTS OF ADJACENT NORTH CENTRAL

    KANSAS/WESTERN IA...

    ...THERE IS A HIGH RISK OF SVR TSTMS LATE THIS AFTERNOON AND EVENING

    ACROSS PARTS OF SOUTH CENTRAL KANSAS INTO NORTH CENTRAL OKLAHOMA...

    ...THERE IS A MDT RISK OF SVR TSTMS SURROUNDING THE HIGH RISK AREA

    ACROSS THE REMAINDER OF CENTRAL AND EASTERN NEBRASKA...WESTERN

    IOWA...NORTHWEST MISSOURI...CENTRAL AND EASTERN KANSAS...AND PARTS

    OF NORTHERN AND CENTRAL OKLAHOMA...

    ...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MODERATE RISK

    AREA ACROSS A LARGE PORTION OF THE CENTRAL AND SOUTHERN PLAINS...

    ...SYNOPSIS...

    MODELS ALL INDICATE THAT A STRONG MID/UPPER JET STREAK...NOW DIGGING

    INTO THE BASE OF A LARGE-SCALE UPPER TROUGH OVER THE WESTERN

    U.S...WILL CONTINUE EASTWARD ACROSS THE SOUTHERN PLATEAU

    TODAY...BEFORE NOSING NORTHEASTWARD ACROSS THE SOUTHERN ROCKIES INTO

    THE CENTRAL PLAINS BY LATE TONIGHT. THIS IS EXPECTED TO INCLUDE A

    90-100+ KT 500 MB JET CORE...WHICH MAY BE PRECEDED BY ANOTHER

    SIGNIFICANT SPEED MAXIMUM ACROSS THE SOUTHERN ROCKIES/ CENTRAL

    PLAINS REGION DURING THE DAY. GUIDANCE SUGGESTS THAT ASSOCIATED

    FORCING WILL CONTRIBUTE TO RAPID INTENSIFICATION OF A SURFACE

    CYCLONE TO THE LEE OF THE CENTRAL ROCKIES...WITH A 1000 MB LOW

    CENTER DEEPENING BELOW 990 MB ACROSS EASTERN COLORADO INTO SOUTHWEST

    NEBRASKA BETWEEN 14/12Z AND 15/00Z. WITHIN ITS WARM SECTOR...A

    SOUTHERLY LOW-LEVEL JET WILL STRENGTHEN ACROSS THE SOUTHERN INTO

    CENTRAL PLAINS /50+ KT AT 850 MB BY LATE AFTERNOON...INCREASING UP

    TO 70 KT DURING THE EVENING/. THIS WILL CONTRIBUTE TO THE

    CONTINUING NORTHWARD ADVECTION OF INCREASINGLY RICH MOISTURE

    RETURNING OFF THE WESTERN GULF OF MEXICO...BENEATH AT LEAST MODESTLY

    STEEP LAPSE RATES. MIXED LAYER CAPE IS EXPECTED TO EXCEED 2000 J/KG

    WITHIN A CORRIDOR ACROSS CENTRAL TEXAS THROUGH MUCH OF OKLAHOMA AND

    CENTRAL/EASTERN KANSAS...INTO THE VICINITY OF A WARM FRONTAL ZONE

    EXTENDING EAST OF THE LOW ACROSS NEBRASKA INTO THE MISSOURI VALLEY.

    THIS ENVIRONMENT IS EXPECTED TO BE CONDUCIVE FOR A SIGNIFICANT

    OUTBREAK OF SEVERE STORMS...THAT MAY IMPACT PORTIONS OF THE CENTRAL

    AND SOUTHERN PLAINS THROUGH MUCH OF THE PERIOD. THIS MAY INCLUDE

    SEVERAL TORNADIC SUPERCELLS...AND PERHAPS...BY TONIGHT... THE

    EVOLUTION OF A SUBSTANTIAL SQUALL LINE.

    ...NEBRASKA...

    NORTH AND EAST OF THE DRY LINE WRAPPING INTO THE DEEPENING SURFACE

    CYCLONE...INTO THE VICINITY OF THE WARM FRONT...CONDITIONS APPEAR

    LIKELY TO BECOME VERY CONDUCIVE TO THE FORMATION OF DISCRETE

    TORNADIC SUPERCELLS...AS THE EXIT REGION OF THE CYCLONIC MID/UPPER

    JET OVERSPREADS THE REGION. THIS COULD OCCUR AS EARLY AS

    18-21Z...IF NOT BEFORE...ACROSS PARTS OF SOUTHWEST INTO CENTRAL

    NEBRASKA...BEFORE DEVELOPING EASTWARD AND INCREASING IN COVERAGE

    ACROSS CENTRAL INTO EASTERN NEBRASKA THROUGH THE REMAINDER OF THE

    AFTERNOON. THIS IS WHERE LOW-LEVEL HODOGRAPHS ARE EXPECTED TO

    BECOME LARGE AND CLOCKWISE CURVED...AND SUPPORTIVE OF LONG-LIVED

    SUPERCELLS CAPABLE OF PRODUCING STRONG TORNADOES.

    ...KANSAS AND OKLAHOMA INTO NORTH CENTRAL/NORTHWEST TEXAS...

    BARRING COMPLICATIONS FROM RESIDUAL EARLY DAY CONVECTIVE

    DEVELOPMENT...THE WARM SECTOR ENVIRONMENT AHEAD OF THE DRY LINE

    ACROSS MUCH OF CENTRAL/EASTERN KANSAS AND OKLAHOMA PROBABLY WILL

    STILL BE CAPABLE OF SUPPORTING LONG-LIVED SUPERCELLS CAPABLE OF

    PRODUCING STRONG TORNADOES. HOWEVER...CONCERN EXISTS THAT THE

    POTENTIAL COVERAGE OF DISCRETE SUPERCELL STORMS MAY REMAIN SOMEWHAT

    SPARSE...PRIOR TO SQUALL LINE EVOLUTION THIS EVENING AS A COLD FRONT

    OVERTAKES THE DRY LINE AND SURGES EASTWARD ACROSS THE PLAINS. ONCE

    THIS OCCURS...DAMAGING WIND AND LARGE HAIL MAY BECOME THE PRIMARY

    SEVERE THREAT.

    ..KERR/LEITMAN.. 04/14/2012

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