mardi 28 avril 2015

European Storm Forecast Experiment

Storm Forecast
Storm Forecast
Valid: Wed 29 Apr 2015 06:00 to Thu 30 Apr 2015 06:00 UTC
Issued: Tue 28 Apr 2015 20:39
Forecaster: PUCIK
A level 1 was issued for NW Russia mainly for severe wind gusts and tornadoes.

SYNOPSIS

Europe will generally be under a broad area of low geopotentials during the forecast period with numerous embedded troughs. The most prominent one will quickly cross the Baltic States towards the continent, inducing cyclogenesis over the Baltic Sea and S Finland. Especially warm and cold front of the deepening low may serve as foci for severe weather over NW Russia and this region will be covered in more detail below. Otherwise, isolated to scattered DMC is forecast with the other troughs, especially in their cores, where cold mid-level temperatures induce steeper lapse rates. However, chances of severe weather in the other areas with possible DMC will be very low, not warranting any Lvl.

lundi 27 avril 2015

Continental Europe animation

European Storm Forecast Experiment

Storm Forecast
Storm Forecast
Valid: Mon 27 Apr 2015 06:00 to Tue 28 Apr 2015 06:00 UTC
Issued: Mon 27 Apr 2015 04:04
Forecaster: VAN DER VELDE
A level 1 was issued for Germany, Czech Republic and Poland mainly for large hail.
A level 1 was issued for parts of Italy and southern Adriatic Sea mainly for isolated excessive precipitation and large hail.

SYNOPSIS

A broad mid/upper trough shifts from western Europe into central Europe. Dynamic lifting occurs ahead of a large PV feature moving eastward through the Mediterranean across Italy. North of the Alps, a cold front enters Germany from the northwest and sharpens during the afternoon spanning SW-E across Germany with a convergence line on its warm side and a low pressure core over southeastern Germany. 
Click map for watches

Apr 27, 2015 0600 UTC Day 1 Convective Outlook

DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1154 PM CDT SUN APR 26 2015

   VALID 271200Z - 281200Z

   ...THERE IS AN ENH RISK OF SVR TSTMS FOR SRN LA...

   ...THERE IS A SLGT RISK OF SVR TSTMS FROM EAST TX TO LA AND SRN
   MS/AL...

   ...THERE IS A MRGL RISK OF SVR TSTMS FOR MUCH OF E TX TO THE CNTRL
   GULF COAST...

   ...THERE IS A MRGL RISK OF SVR TSTMS FOR PARTS OF SOUTH FL...

   ...SUMMARY...
   SCATTERED SEVERE THUNDERSTORMS WILL DEVELOP ACROSS PARTS OF
   LOUISIANA THIS MORNING AND AFTERNOON. ADDITIONAL STRONG TO SEVERE
   THUNDERSTORMS ARE POSSIBLE OVER EAST TEXAS...WHILE ISOLATED STRONG
   STORMS ARE POSSIBLE OVER SOUTH FLORIDA.

   ...SYNOPSIS...
   A SRN STREAM CLOSED LOW-MIDLEVEL CYCLONE WILL SLOWLY MOVE EWD ACROSS
   THE SRN PLAINS. AN ATTENDANT UPPER JET WILL EXTEND FROM S TX ACROSS
   THE CNTRL GULF COAST. AT THE SFC...WEAK LOW PRESSURE WILL DEVELOP
   OVER E TX. SEGMENT OF A COLD FRONT WILL BECOME QUASISTATIONARY
   ACROSS THE SOUTHEAST...KEEPING A MARITIME TROPICAL AIR MASS CONFINED
   TO NEAR THE GULF COAST. 

   ...E TX INTO THE CNTRL GULF COAST...
   AN MCS SHOULD BE ONGOING EARLY MON MORNING NEAR THE SABINE VALLEY
   INTO WRN LA. THIS FEATURE IS EXPECTED TO CONTINUE PROGRESSING EWD
   ACROSS THE CNTRL GULF COAST STATES THROUGH LATE MORNING...WITH AN
   ACCOMPANYING DMGG WIND AND ISOLATED TORNADO RISK
   POSSIBLE...ESPECIALLY ALONG/S OF A QUASI-STATIONARY BAROCLINIC ZONE
   ORIENTED GENERALLY W-E. 27/00Z LIX SOUNDING AND SFC OBS SAMPLED RICH
   LOW-LEVEL MOISTURE AND STEEP MIDLEVEL LAPSE RATES IN PLACE...AND
   MLCAPE VALUES SHOULD REACH 1000-1500 J/KG AHEAD OF THE QLCS.
   HERE...TSTMS MAY ALSO DEVELOP INVOF THE BAROCLINIC ZONE AMIDST WEAK
   LOW-LEVEL WAA...AND AN ISOLATED TORNADO THREAT CANNOT BE RULED OUT.

   MEANWHILE...AIR MASS RECOVERY SHOULD OCCUR ACROSS E TX INTO SWRN LA
   IN THE WAKE OF MORNING CONVECTION...ALTHOUGH TO WHAT DEGREE IT CAN
   DESTABILIZE GIVEN THE PRESENCE OF CLOUD COVER REMAINS UNCERTAIN.
   HOWEVER...MOST MODEL GUIDANCE SUGGESTS A NARROW CORRIDOR OF MODERATE
   INSTABILITY WILL EXIST /ROUGHLY FROM HOUSTON TO DALLAS/ IN
   CONJUNCTION WITH DEWPOINTS IN THE 60S E OF A WEAK SFC LOW AND
   ATTENDANT PACIFIC FRONT. VERTICAL WIND PROFILES WOULD BE SUFFICIENT
   FOR SUPERCELLS...BUT CONVECTIVE INITIATION/EVOLUTION WILL BE
   DEPENDENT ON PRESENCE/POSITION OF OUTFLOW BOUNDARIES...AND WHETHER
   ENOUGH HEATING CAN OCCUR TO OVERCOME CINH AND SUPPORT SFC-BASED
   CONVECTION. SCATTERED TSTMS MAY CONTINUE INTO THE LATE EVENING
   ACROSS THE SABINE VALLEY AND ACROSS LA/SRN MS.

   ...SOUTH FL...
   AFTERNOON SEA BREEZE TSTMS ARE FORECAST TO DEVELOP OVER SOUTH FL
   AMIDST VERY WARM DAYTIME TEMPERATURES IN THE 90S. ALTHOUGH LOW-LEVEL
   FLOW WILL BE WEAK...30-40 KT OF MIDLEVEL WLYS COULD SUPPORT
   MARGINALLY ORGANIZED CONVECTION CAPABLE OF PRODUCING LOCALIZED
   STRONG WIND GUSTS AND HAIL.

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Current Convective Watches (View What is a Watch? clip)
Updated:  Mon Apr 27 09:44:10 UTC 2015

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SPC Apr 27, 2015 0600Z Thunderstorm Outlook

Click map for Details from SPC!

dimanche 26 avril 2015

4/26/2015 Ben McMillan Live Storm Chasing Feed from North Texas

https://www.youtube.com/watch?v=o4Qig_NS8rE

Tornado Warning!!!

Stephenville TX Tornado April 26, 2015

https://www.youtube.com/watch?v=HaheBexkBIY

Ben Holcomb

https://tvnweather.com/live

Logo 1434x191,,,,,,,,,,https://tvnweather.com/live

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Current Convective Watches (View What is a Watch? clip)
Updated:  Mon Apr 27 00:39:20 UTC 2015

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4/26/2015 Rising Star, TX Baseball Hail

https://www.youtube.com/watch?v=RAN_4bmKn-s

StormChasingVideo

NOAA Weather Radio!

http://www.spc.noaa.gov/products/md/

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Current Mesoscale Discussions
Updated:  Sun Apr 26 17:47:03 UTC 2015

Valid MD Image
Mesoscale Discussion 466
< Previous MD
MD 466 graphic
   MESOSCALE DISCUSSION 0466
   NWS STORM PREDICTION CENTER NORMAN OK
   1244 PM CDT SUN APR 26 2015

   AREAS AFFECTED...MUCH OF SC

   CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 

   VALID 261744Z - 261945Z

   PROBABILITY OF WATCH ISSUANCE...20 PERCENT

   SUMMARY...AN ISOLATED DAMAGING WIND THREAT MAY DEVELOP THIS
   AFTERNOON ACROSS MUCH OF SC. WW ISSUANCE IS UNLIKELY.

   DISCUSSION...A SLOWLY SWWD MOVING COLD FRONT ACROSS SC SHOULD
   PROVIDE A FOCUS FOR ISOLATED TO WIDELY SCATTERED THUNDERSTORM
   DEVELOPMENT THIS AFTERNOON. SFC TEMPERATURES ALONG AND S OF THIS
   FRONT HAVE WARMED INTO THE UPPER 70S TO LOWER 80S AS OF 17Z...WITH
   DEWPOINTS GENERALLY IN THE 60S ACROSS MUCH OF UPSTATE SC. AS THE
   BOUNDARY LAYER CONTINUES TO WARM FOR THE NEXT SEVERAL HOURS...MLCAPE
   SHOULD INCREASE UP TO 1000-1250 J/KG GIVEN MIDLEVEL LAPSE RATES
   AROUND 6.0-6.5 C/KM. 

   UNIDIRECTIONAL WLY FLOW STRENGTHENING WITH HEIGHT THAT IS ROUGHLY
   PARALLEL TO THE SFC BOUNDARY MAY PROMOTE INITIAL SUPERCELL
   DEVELOPMENT THAT COULD GROW UPSCALE INTO MULTICELL/BOWING
   STRUCTURES...WITH AN ASSOCIATED RISK FOR STRONG TO ISOLATED DAMAGING
   WIND GUSTS...AND PERHAPS SOME HAIL. AREA RADARS DEPICT ELEVATED
   SHOWERS THAT HAVE RECENTLY FORMED OVER CHEROKEE COUNTY SC TO THE
   COOL SIDE OF THE FRONT...WHICH COUPLED WITH A DEEPENING CUMULUS
   FIELD ON VISIBLE SATELLITE...MAY SIGNAL THAT CONVECTION WILL DEVELOP
   WITHIN THE NEXT HOUR OR TWO.

   REGARDLESS...THE MARGINAL THERMODYNAMIC ENVIRONMENT WILL PROBABLY
   ACT TO LIMIT A MORE ROBUST SEVERE THREAT ACROSS THE MCD AREA THIS
   AFTERNOON. THEREFORE...WW ISSUANCE IS UNLIKELY AT THIS TIME.

   ..GLEASON/MEAD.. 04/26/2015
Mesoscale Discussion 465
< Previous MD         Next MD >
MD 465 graphic
   MESOSCALE DISCUSSION 0465
   NWS STORM PREDICTION CENTER NORMAN OK
   1055 AM CDT SUN APR 26 2015

   AREAS AFFECTED...PARTS OF NORTHWEST/NORTH-CENTRAL TX INCLUDING TX
   BIG COUNTRY INTO SOUTHERN OK

   CONCERNING...SEVERE POTENTIAL...WATCH LIKELY 

   VALID 261555Z - 261800Z

   PROBABILITY OF WATCH ISSUANCE...95 PERCENT

   SUMMARY...THUNDERSTORMS ARE EXPECTED TO STEADILY INCREASE THROUGH
   LATE MORNING/AFTERNOON AND INTENSIFY ACROSS PORTIONS OF THE
   NORTHWEST/NORTH-CENTRAL TX...AND EVENTUALLY REACH PORTIONS OF
   SOUTHERN OK LATER THIS AFTERNOON. INITIALLY ELEVATED STORMS COULD
   POSE A HAIL RISK LATE THIS MORNING...WHILE THE POTENTIAL FOR
   SURFACE-BASED SEVERE THUNDERSTORMS OTHERWISE INCREASES THIS
   AFTERNOON. THE NEED FOR A WATCH WILL BECOME INCREASINGLY LIKELY BY
   MIDDAY/EARLY AFTERNOON.

   DISCUSSION...MULTIPLE BANDS OF INITIALLY ELEVATED THUNDERSTORMS HAVE
   INCREASED ACROSS PARTS OF THE TX BIG COUNTRY SINCE MID-MORNING
   GENERALLY NEAR THE ABILENE AREA AS OF 1530Z. THIS GENERAL INCREASE
   SEEMS VERY LIKELY TO CONTINUE...PARTICULARLY GIVEN THAT
   EAST-NORTHEASTWARD-SHIFTING IMPLIED INCREASING FORCING-FOR-ASCENT IS
   READILY APPARENT INTO WEST TX PER MORNING IR/WV SATELLITE TRENDS. 

   SEVERE HAIL MAY BE THE INITIAL RISK LATE THIS MORNING. HOWEVER...AS
   MIDDLE/UPPER 60S F SURFACE DEWPOINTS CONTINUE TO STEADILY STREAM
   NORTHWARD WITHIN A BROADENING MOIST SECTOR...DEVELOPMENT SHOULD
   INCREASINGLY CONNECT WITH THE BOUNDARY LAYER WITH SURFACE-BASED
   STORMS BECOMING AN INCREASING CONCERN THIS AFTERNOON...INITIALLY
   ACROSS PORTIONS OF NORTHWEST/NORTH-CENTRAL TX.
   ACCORDINGLY...ISOLATED TORNADO AND DAMAGING WIND POTENTIAL SHOULD
   ALSO INCREASE.

Large Hail, Damaging Winds, Tornadoes, and Flooding Possible Today - 4/2...

Apr 26, 2015 1300 UTC Day 1 Convective Outlook

DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1128 AM CDT SUN APR 26 2015

   VALID 261630Z - 271200Z

   ...THERE IS A MDT RISK OF SVR TSTMS OVER PARTS OF NRN AND CNTRL
   TX...

   ...THERE IS AN ENH RISK OF SVR TSTMS FROM NRN INTO CNTRL AND ERN
   TX...

   ...THERE IS A SLGT RISK OF SVR TSTMS OVER THE SRN PLAINS...

   ...THERE IS A MRGL RISK OF SVR TSTMS OVER THE SRN PLAINS...

   ...THERE IS A MRGL RISK OF SVR TSTMS OVER A PART OF THE FL
   PENINSULA...

   ...THERE IS A MRGL RISK OF SVR TSTMS OVER SC...

   ...SUMMARY...
   SCATTERED SEVERE THUNDERSTORMS ARE EXPECTED OVER PARTS OF THE
   SOUTHERN PLAINS THIS AFTERNOON THROUGH TONIGHT...WITH THE STORMS
   SPREADING SOUTH AND EAST TOWARD THE TEXAS GULF COAST EARLY MONDAY. 
   VERY LARGE HAIL...TORNADOES...A COUPLE OF WHICH COULD BE
   STRONG...AND DAMAGING WINDS WILL ACCOMPANY THESE STORMS. ISOLATED
   STRONG TO POTENTIALLY SEVERE STORMS ALSO MAY OCCUR THIS AFTERNOON
   OVER PARTS OF SOUTH CAROLINA AND FLORIDA.

   ...SYNOPSIS...

   THE SRN SEGMENT OF AN AMPLIFIED TROUGH OVER THE INTERIOR WEST WILL
   FORM A CLOSED UPPER LOW WHICH WILL DEVELOP FROM THE SRN ROCKIES INTO
   SRN HIGH PLAINS BY 12Z/MONDAY.  AN ASSOCIATED 70-80 KT MID-LEVEL JET
   STREAK CURRENTLY ROUNDING THE TROUGH BASE OVER NWRN MEXICO WILL
   DEVELOP EWD INTO CNTRL TX WITHIN THE SRN SEMICIRCLE OF THE EVOLVING
   LOW.

   AT THE SURFACE...A LEE CYCLONE OVER ERN NM WILL DEVELOP GENERALLY
   ESEWD INTO CNTRL TX IN RESPONSE TO THE EVOLVING UPPER LOW WITH A
   DRYLINE BECOMING ESTABLISHED BY AFTERNOON FROM THE VICINITY OF THE
   SURFACE LOW SWD INTO THE EDWARDS PLATEAU.  MEANWHILE...A BACKING AND
   STRENGTHENING LOW-LEVEL FLOW REGIME WILL PROMOTE THE NWD MOVEMENT OF
   A WARM FRONT THROUGH THE RED RIVER VALLEY.

   ...SRN PLAINS TODAY THROUGH TONIGHT...

   MID-MORNING SATELLITE DATA INDICATE A BELT OF IMPLIED ASCENT
   SPREADING EWD THROUGH FAR WRN TX AND FAR ERN NM IN ASSOCIATION WITH
   A LEAD VORTICITY MAXIMUM PRECEDING THE MAIN UPPER-AIR SYSTEM.  AT
   THE SAME TIME...AN INCREASINGLY MOIST BOUNDARY LAYER IS RAPIDLY
   DEVELOPING NWD THROUGH W-CNTRL TX ALONG AND TO THE S OF THE WARM
   FRONT AND BENEATH A PLUME OF STEEP MID-LEVEL LAPSE RATES /SEE 12Z
   DRT SOUNDING/.  THE OVERLAP OF THESE PROCESSES SHOULD FOSTER AN
   INCREASE IN MAINLY ELEVATED TSTMS LATE THIS MORNING INTO AFTERNOON
   NWD THROUGH THE RED RIVER VALLEY.  INCREASING CLOUD-BEARING SHEAR
   AND THE DESTABILIZING ENVIRONMENT WILL PROMOTE VIGOROUS UPDRAFTS
   WITH A RISK FOR PRIMARILY LARGE HAIL.  FOR ADDITIONAL
   INFORMATION...SEE MCD 465.

   IN THE WAKE OF THIS EARLY-DAY ACTIVITY OR ALONG ITS SRN
   FLANK...SURFACE-BASED STORM DEVELOPMENT IS EXPECTED TO OCCUR BY MID
   TO LATE AFTERNOON INTO EVENING FROM THE VICINITY OF THE SURFACE
   TRIPLE POINT OVER NWRN TX SWD ALONG THE DRYLINE.  THIS ACTIVITY WILL
   BE ENCOURAGED BY THE FORCING FOR ASCENT WITHIN THE EXIT REGION OF
   THE MID-LEVEL JET STREAK EMERGING FROM SWRN TX WHERE THE COMBINATION
   OF 1500-2000+ J/KG MLCAPE AND STEADILY STRENGTHENING LOW-LEVEL AND
   DEEP-LAYER SHEAR WILL PROMOTE INTENSE SUPERCELLS CAPABLE OF VERY
   LARGE HAIL AND TORNADOES...SOME OF WHICH COULD BE STRONG.

   EXPECT STORMS TO GROW UPSCALE INTO ONE OR MULTIPLE MCSS OVERNIGHT
   WITH THE RISK FOR POTENTIALLY MORE WIDESPREAD DAMAGING WINDS
   INCREASING ACROSS PORTIONS OF CNTRL INTO ERN TX.  LARGE HAIL AND A
   FEW TORNADOES WILL ALSO REMAIN A CONCERN.  

   ...FL TODAY...

   TSTMS HAVE INCREASED IN AREAL COVERAGE THIS MORNING ALONG A RESIDUAL
   OUTFLOW BOUNDARY/CONFLUENCE ZONE FROM THE FAR NERN GULF OF MEXICO
   EWD ALONG AN OCF-DAB LINE.  TO THE SOUTH OF THIS ACTIVITY...DIABATIC
   SURFACE HEATING IN CONJUNCTION WITH BOUNDARY-LAYER DEWPOINTS IN THE
   LOWER 70S SHOULD RESULT MODERATE AFTERNOON INSTABILITY AMIDST A
   KINEMATIC ENVIRONMENT EXHIBITING A RELATIVELY STRONG WLY DEEP-LAYER
   WIND FIELD.  AS SUCH...THE POTENTIAL WILL EXIST FOR SOME SUPERCELL
   AND/OR BOWING STRUCTURES CAPABLE OF MAINLY DAMAGING WIND GUSTS.

   FOR ADDITIONAL NEAR-TERM GUIDANCE...SEE MCD 464.

   ...SC THIS AFTERNOON...

   HEATING OF A MOIST AIR MASS PRECEDING A SWD-MOVING COLD FRONT WILL
   SUPPORT THE DEVELOPMENT OF STEEP LOW-LEVEL LAPSE RATES AND AT LEAST
   A MARGINALLY UNSTABLE AIR MASS LATER TODAY.  DIRECT THERMAL
   CIRCULATIONS ARISING FROM DIFFERENTIAL HEATING ALONG THE FRONT
   SHOULD FOSTER A FEW STORMS BY AFTERNOON WITH LOCALLY STRONG WIND
   GUSTS POSSIBLE OWING TO THE DOWNWARD TRANSPORT OF STRONG WNWLY FLOW
   ALOFT.
Mesoscale Discussion 464
< Previous MD
MD 464 graphic
   MESOSCALE DISCUSSION 0464
   NWS STORM PREDICTION CENTER NORMAN OK
   0931 AM CDT SUN APR 26 2015

   AREAS AFFECTED...NORTH-CENTRAL FL PENINSULA

   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

   VALID 261431Z - 261700Z

   PROBABILITY OF WATCH ISSUANCE...40 PERCENT

   SUMMARY...STORMS SHOULD CONTINUE TO INCREASE/MOVE INLAND AND
   INTENSIFY ACROSS THE NORTH-CENTRAL FL PENINSULA THROUGH THE LATE
   MORNING/EARLY AFTERNOON HOURS. ISOLATED DAMAGING WINDS AND SOME
   SEVERE HAIL WILL BE POSSIBLE.

   DISCUSSION...LARGELY RELATED TO PRIOR DAY CONVECTION/OUTFLOW...AN
   EFFECTIVE SURFACE BOUNDARY AND RELATED ZONE OF
   CONFLUENCE/DIFFERENTIAL HEATING EXTENDS IN A WEST-EAST ORIENTATION
   ACROSS THE NORTH-CENTRAL FL PENINSULA. THE 12Z OBSERVED SOUNDING
   FROM TAMPA BAY SAMPLES THE MOIST/MODERATELY UNSTABLE AIR MASS THAT
   EXISTS NEAR/SOUTH OF THE AFOREMENTIONED BOUNDARY...WHERE MLCAPE IS
   LIKELY TO REACH 1500-2000 J/KG BY MIDDAY AMID WEAKENING BOUNDARY
   LAYER INHIBITION. 

   CURRENT THINKING IS THAT ONGOING STRONG STORMS OVER THE FAR
   NORTHEAST GULF OF MEXICO WILL MOVE INLAND THROUGH LATE MORNING/EARLY
   AFTERNOON...WHILE STORMS OTHERWISE INTENSIFY IN VICINITY OF THE
   WEST-EAST ORIENTED EFFECTIVE BOUNDARY. THE STRONGEST ACTIVITY MAY
   MATERIALIZE NEAR THE NORTHEAST/EAST-CENTRAL FL COAST WHERE
   CONVERGENCE IS MAXIMIZED IN VICINITY OF SEA BREEZE DEVELOPMENT.
   REGARDLESS...ISOLATED DAMAGING WINDS/SOME SEVERE HAIL WILL BE
   POSSIBLE. WITH STORM ORGANIZATION/SUSTENANCE AIDED BY STRONG
   MID-LEVEL WINDS /30-50 KT BETWEEN 3-6 KM AGL/...STORMS ARE LIKELY TO
   EVENTUALLY CLUSTER AS THEY MOVE EAST-SOUTHEASTWARD ACROSS THE
   NORTH-CENTRAL PENINSULA THIS AFTERNOON.

SPC Apr 26, 2015 1300Z Thunderstorm Outlook

Today's Forecast Map

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Continental Europe animation

European Storm Forecast Experiment

Storm Forecast
Storm Forecast
Valid: Sun 26 Apr 2015 06:00 to Mon 27 Apr 2015 06:00 UTC
Issued: Sun 26 Apr 2015 06:09
Forecaster: GATZEN
A level 1 was issued for eastern Spain mainly for large hail.

A level 1 was issued for southern France mainly for large hail and excessive precipitation.

A level 1 was issued for central France mainly for large hail.

A level 1 was issued for central and northern Belaus mainly for large hail.

A level 1 was issued for central Austria mainly for large hail.

A level 1 was issued for north-eastern Algeria mainly for large hail.

SYNOPSIS

At the southern flank of an intense long-wave trough over NW Europe, a former closed low migrates east, crossing the Iberian Peninsula and western France today. A strong jet streak rapidly spreads east over northern Morocco and Algeria, providing strong DCVA from southern Iberia into the W Mediterranean. Downstream of this trough, a weakening south-westerly flow affects Central Europe, whereas broad low geopotential with cold mid-levels remains across most of eastern Europe.

At lower levels, rather warm air masses extend from the west Mediterranean into central and eastern Europe. Increasing lapse rates are expected from the Mediterranean to the Alps, across the Balkans, and over parts of eastern Europe. Given increasing low-level moisture as well, a broad area of CAPE is expected in response to diurnal heating to the south of a cold front that extends over northern France, Germany, Poland, and Belarus. Weak CAPE is present from south-eastern Europe to the southern Mediterranean.

vendredi 24 avril 2015

Watches: Tornado in red Severe T-storm in blue

Click map for watches

Apr 24, 2015 0600 UTC Day 1 Convective Outlook

DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1253 AM CDT FRI APR 24 2015

   VALID 241200Z - 251200Z

   ...THERE IS AN ENH RISK OF SVR TSTMS THIS AFTERNOON AND EVENING
   ACROSS PARTS OF CENTRAL AND EASTERN KANSAS...

   ...THERE IS AN ENH RISK OF SVR TSTMS ACROSS PARTS OF NORTH CENTRAL
   AND NORTHEAST TEXAS INTO ADJACENT PORTIONS OF SOUTHERN OKLAHOMA AND
   THE ARKLATEX...

   ...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE ENH RISK
   AREAS...ACROSS MUCH OF THE CENTRAL AND SOUTHERN PLAINS INTO WESTERN
   GULF COASTAL AREAS AND THE LOWER MISSISSIPPI VALLEY...

   ...THERE IS A MRGL RISK OF SVR TSTMS AS FAR NORTH AS PORTIONS OF THE
   NORTHERN PLAINS...AND AS FAR EAST AS THE CENTRAL GULF STATES...

   ...SUMMARY...
   SEVERE THUNDERSTORMS ARE LIKELY THIS AFTERNOON INTO TONIGHT ACROSS
   THE CENTRAL AND SOUTHERN PLAINS.  THIS WILL INCLUDE THE RISK FOR
   SUPERCELLS CAPABLE OF PRODUCING VERY LARGE HAIL AND PERHAPS A FEW
   STRONG TORNADOES...MAINLY ACROSS PARTS OF CENTRAL KANSAS...AS WELL
   AS PARTS OF NORTHEAST TEXAS INTO ADJACENT PORTIONS OF SOUTHERN
   OKLAHOMA AND THE ARKLATEX REGION.

   ...SYNOPSIS...
   A PAIR OF CLOSED LOWS WITHIN THE NORTHERN BRANCH OF SPLIT WESTERLIES
   EMANATING FROM THE MID-LATITUDE PACIFIC MAY ONLY SHIFT SLOWLY
   EASTWARD OR SOUTHEASTWARD TODAY...ONE OFF THE NEW ENGLAND
   COAST...THE OTHER INTO SOUTHERN BRITISH COLUMBIA AND THE PACIFIC
   NORTHWEST.  BETWEEN THESE TWO FEATURES...THOUGH...WITHIN THE
   SOUTHERN BRANCH...A VIGOROUS SHORT WAVE IMPULSE IS FORECAST TO
   ACCELERATE EAST NORTHEASTWARD OUT OF THE SOUTHWESTERN STATES...IN
   PHASE WITH THE SUBTROPICAL STREAM.  ASSOCIATED FORCING FOR UPWARD
   VERTICAL MOTION APPEARS LIKELY TO CONTRIBUTE TO SIGNIFICANT SURFACE
   CYCLOGENESIS TO THE LEE OF THE CENTRAL ROCKIES BY LATE THIS
   AFTERNOON...BEFORE CONTINUING EAST NORTHEASTWARD INTO THE MID/LOWER
   MISSOURI VALLEY BY LATE TONIGHT.

   IN THE WAKE OF DRY/POTENTIALLY COLD AIR ASSOCIATED WITH THE EASTERN
   CLOSED LOW...WHICH IS STILL SETTLING INTO THE SOUTHEASTERN U.S...A
   WEDGE OF LOW-LEVEL MOISTURE RETURN INTO THE SOUTHERN PLAINS MAY
   CONTINUE TO SLOWLY ADVECT NORTHWARD TOWARD THE CENTRAL
   PLAINS...GRADUALLY WRAPPING INTO THE VICINITY OF THE DEEPENING LOW
   CENTER.  THIS MOISTURE...COUPLED WITH INCREASING LARGE-SCALE ASCENT
   IS EXPECTED TO SUPPORT CONSIDERABLE THUNDERSTORM ACTIVITY ACROSS THE
   PLAINS AND MISSISSIPPI VALLEY REGION.  SOME OF THIS ACTIVITY IS
   EXPECTED TO BE SEVERE...ACCOMPANIED BY THE RISK FOR LARGE
   HAIL...DAMAGING WIND GUSTS...AND A FEW TORNADOES.

   OTHERWISE...SCATTERED AFTERNOON AND EVENING THUNDERSTORMS ARE AGAIN
   EXPECTED ACROSS PARTS OF THE INTERMOUNTAIN WEST AND ROCKIES...AND
   PARTS OF SOUTHERN FLORIDA.

   ...CENTRAL/SOUTHERN PLAINS INTO LOWER MISSISSIPPI VALLEY...
   WHILE THE EVOLVING LARGE-SCALE PATTERN COULD SUPPORT EVEN MORE
   SUBSTANTIVE SEVERE WEATHER POTENTIAL THAN CURRENTLY INDICATED...A
   NUMBER OF UNCERTAINTIES DO EXIST WHICH PRECLUDE HIGHER SEVERE
   PROBABILITIES AT THE PRESENT TIME.  THIS INCLUDES THE LIKELIHOOD OF
   CONSIDERABLE EARLY PERIOD MID/UPPER CLOUD COVER ASSOCIATED WITH A
   CIRRUS SHIELD ACCOMPANYING THE SUBTROPICAL JET...AND AREAS OF
   CONVECTIVE DEVELOPMENT WITHIN THE RETURNING MOIST PLUME. 
   THUNDERSTORM ACTIVITY MAY BE ONGOING THIS MORNING ACROSS MUCH OF
   NORTHERN/EASTERN TEXAS...AS WELL AS NEAR MID/UPPER TEXAS GULF
   COASTAL AREAS.  IT IS UNCLEAR WHAT IMPACT THIS WILL HAVE ON
   SUBSEQUENT DEVELOPING WARM SECTOR INSTABILITY...INCLUDING MOISTURE
   RETURN TO THE CENTRAL PLAINS.

   REGARDLESS...FORCING IN THE EXIT REGION OF A 70-80+ KT 500 MB JET
   NOSING INTO THE CENTRAL PLAINS...AND A STRONGLY DIFLUENT UPPER FLOW
   REGIME OVERSPREADING NORTH TEXAS /JUST NORTH OF THE SUBTROPICAL JET
   AXIS...AHEAD OF THE BASE OF THE SHORT WAVE TROUGH ADVANCING INTO THE
   PLAINS/...PROBABLY WILL PROVIDE THE FOCUS FOR THE PRIMARY SEVERE
   WEATHER POTENTIAL LATE THIS AFTERNOON AND EVENING.  MOISTURE WILL BE
   MORE SUBSTANTIVE ACROSS THE SOUTHERN AREA...WHERE MID-LEVEL LAPSE
   RATES MAY BE WEAKER...WHILE STEEPER MID-LEVEL LAPSE RATES ACROSS THE
    NORTHERN AREA MAY COMPENSATE FOR MORE LIMITED LOW-LEVEL MOISTURE
   RETURN.

   BY 21-23Z...THE ENVIRONMENT PROBABLY WILL BE CONDUCIVE TO SUPERCELL
   STORMS ALONG THE DRYLINE...AND NEAR THE WARM FRONT... ACROSS PARTS
   OF CENTRAL KANSAS.  STRONGEST ACTIVITY IS EXPECTED TO BE CAPABLE OF
   PRODUCING VERY LARGE HAIL AND TORNADOES...A COUPLE OF WHICH COULD BE
   STRONG...BEFORE WEAKENING AS IT SPREADS EASTWARD THIS EVENING.

   TIMING IS A BIT MORE UNCERTAIN ACROSS PARTS OF NORTHERN TEXAS... BUT
   IT MAY BE CLOSER TO...OR AFTER...25/00Z...WHEN LARGE-SCALE FORCING
   AND INSTABILITY MAY SUPPORT AN UPSCALE GROWING MESOSCALE CONVECTIVE
   SYSTEM.  VERY LARGE HAIL MAY BE POSSIBLE WITH INITIAL
   ACTIVITY...BEFORE THE RISK OF DAMAGING WIND GUSTS BECOMES MORE
   PROMINENT DURING THE EVENING.  IT IS POSSIBLE THAT THE EVOLVING
   CONVECTIVE SYSTEM COULD BE PRECEDED BY DISCRETE SUPERCELL STORMS
   WHICH COULD POSE A MORE APPRECIABLE RISK FOR
   TORNADOES...PARTICULARLY AS ACTIVITY SPREADS TOWARD THE ARKLATEX
   REGION...COINCIDENT WITH STRENGTHENING OF INITIALLY MODEST SOUTHERLY
   850 MB FLOW FIELDS.

jeudi 23 avril 2015

European Storm Forecast Experiment

Storm Forecast
Storm Forecast
Valid: Thu 23 Apr 2015 06:00 to Fri 24 Apr 2015 06:00 UTC
Issued: Wed 22 Apr 2015 15:40
Forecaster: GATZEN
A level 1 was issued for northern Algeria and Tunisia mainly for large hail.

SYNOPSIS

High-over-low blocking is present across the NE Atlantic, yielding a southern branch of the westerly jet that extends across the northern Iberian Peninsula into the Mediterranean. The northern portion of the westerly jet is located across Scandinavia into Russia. In between, a cut-off low is located over the eastern Alps. Pretty marginal low-level moisture can be expected over most areas. Locally enhanced moisture exceeding 7 g/kg in the lowest 500 m is indicated by latest GFS model along the southern flanks of the Alps, across the south-west Mediterranean, and from the Bay of Biscay into south-western France. Low-level moisture partly overlaps with steeper lapse rates evolving near the Alpine cut-off low and across the south-west Mediterranean area.

Apr 23, 2015 0600 UTC Day 1 Convective Outlook

DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1249 AM CDT THU APR 23 2015

   VALID 231200Z - 241200Z

   ...THERE IS A SLGT RISK OF SVR TSTMS FROM MIDDAY INTO THE AFTERNOON
   ACROSS PARTS OF SOUTHERN LOUISIANA...

   ...THERE IS A SLGT RISK OF SVR TSTMS LATE THIS AFTERNOON AND EVENING
   ACROSS PARTS OF NORTHWEST TEXAS AND ADJACENT SOUTHWESTERN
   OKLAHOMA...SOUTHWARD ACROSS THE EDWARDS PLATEAU INTO ADJACENT AREAS
   OF THE RIO GRANDE VALLEY...

   ...THERE IS A MRGL RISK OF SVR TSTMS SURROUNDING THE SLIGHT RISK
   AREAS....ACROSS THE CENTRAL PLAINS AND SOUTHERN PLAINS INTO THE
   CENTRAL GULF COAST...

   ...THERE IS A MRGL RISK OF SVR TSTMS THIS AFTERNOON ACROSS SOUTHEAST
   FLORIDA COASTAL AREAS...

   ...SUMMARY...
   SCATTERED STRONG TO SEVERE THUNDERSTORMS ARE POSSIBLE TODAY ACROSS
   THE CENTRAL HIGH PLAINS...THE SOUTHERN PLAINS...THE CENTRAL GULF
   COAST REGION...AND SOUTHEAST FLORIDA COASTAL AREAS.

   ...SYNOPSIS...
   WITHIN THE NORTHERN BRANCH OF SPLIT WESTERLIES EMANATING FROM THE
   MID-LATITUDE PACIFIC...MODELS INDICATE THAT THE CENTER OF A
   LARGE...COLD MID/UPPER LOW WILL REDEVELOP EASTWARD DURING THIS
   PERIOD...FROM EASTERN ONTARIO INTO NORTHERN NEW ENGLAND BY 12Z
   FRIDAY.  AS THIS OCCURS...AND AN UPSTREAM CLOSED LOW GRADUALLY
   MIGRATES INLAND ACROSS THE SOUTHERN BRITISH COLUMBIA/WASHINGTON
   COAST...UPPER TROUGHING WITHIN THE SOUTHERN BRANCH...IN PHASE WITH
   THE SUBTROPICAL STREAM...IS FORECAST TO DEVELOP EAST NORTHEASTWARD
   TOWARD THE CENTRAL AND SOUTHERN ROCKIES.  AS THE MOST PROMINENT
   SHORT WAVE IMPULSE WITHIN THIS LATTER FEATURE SLOWLY PIVOTS ACROSS
   BAJA AND THE GULF OF CALIFORNIA...BEFORE ACCELERATING NORTHEASTWARD
   TOWARD THE SOUTHERN ROCKIES...DOWNSTREAM SHORT WAVE RIDGING APPEARS
   LIKELY TO AMPLIFY ACROSS PARTS OF THE CENTRAL/SOUTHERN PLAINS
   THROUGH MID/LOWER MISSISSIPPI VALLEY.

   IN LOWER LEVELS...FURTHER SOUTHWARD ADVANCEMENT OF A COLD FRONT
   THROUGH THE SOUTH ATLANTIC /EASTERN GULF COAST STATES IS EXPECTED. 
   THE TRAILING WESTERN FLANK OF THIS FRONT PROBABLY WILL REMAIN
   STALLED NEAR/NORTH OF THE SOUTHERN PLAINS RED RIVER VALLEY THROUGH
   THE DAY...BEFORE REDEVELOPING NORTHWARD INTO THE CENTRAL PLAINS
   TONIGHT.  AT THE SAME TIME...SURFACE TROUGHING SHOULD BEGIN TO
   GRADUALLY DEEPEN ACROSS THE HIGH PLAINS.  SEASONABLY MOIST AIR WILL
   REMAIN CONFINED TO AREAS ALONG AND SOUTH OF THE FRONT...BUT SOME
   INCREASE IN MOISTURE IS ALSO EXPECTED AS SOUTHEASTERLY/SOUTHERLY
   LOW-LEVEL FLOW STRENGTHENS ACROSS THE HIGH PLAINS.

   BENEATH SEASONABLY STEEP MID-LEVEL LAPSE RATES...THIS MOISTURE...
   COUPLED WITH DAYTIME HEATING...WILL CONTRIBUTE TO SCATTERED
   THUNDERSTORM ACTIVITY ACROSS THE HIGH PLAINS...PORTIONS OF THE
   CENTRAL GULF COAST STATES...AND THE FLORIDA ATLANTIC COASTAL AREAS. 
   ADDITIONAL SCATTERED THUNDERSTORM ACTIVITY LIKELY WILL FORM WITH
   DAYTIME HEATING ACROSS PARTS OF THE CENTRAL ROCKIES...THE GREAT
   BASIN...THE SIERRA NEVADA AND ADJACENT INTERIOR VALLEYS OF
   CALIFORNIA...AND THE MOGOLLON RIM AREA OF ARIZONA INTO THE MOUNTAINS
   OF SOUTHWESTERN NEW MEXICO.  WHILE MUCH OF THIS ACTIVITY DIMINISHES
   THIS EVENING...INCREASING LARGE-SCALE ASCENT DOWNSTREAM OF THE
   SOUTHERN BRANCH TROUGHING IS EXPECTED TO PROVIDE THE FORCING/FOCUS
   FOR NEW STORM DEVELOPMENT ACROSS PARTS OF THE CENTRAL AND SOUTHERN
   PLAINS.

   ...TEXAS AND ADJACENT SOUTHERN OKLAHOMA...
   MOISTURE CONTENT IS EXPECTED TO REMAIN SUPPORTIVE OF SIZABLE MIXED
   LAYER CAPE BY LATE AFTERNOON BENEATH RELATIVELY STEEP MID-LEVEL
   LAPSE RATES.  IN THE PRESENCE OF STRONG DEEP LAYER VERTICAL SHEAR
   BENEATH 40-50+ KT SOUTHWESTERLY 500 MB FLOW...THE ENVIRONMENT SHOULD
   BE CONDUCIVE TO SEVERE STORMS...INCLUDING SUPERCELLS...WHERE DEEP
   CONVECTION CAN BE INITIATED AND MAINTAINED.  THE DRYLINE SEEMS TO
   PROVIDE THE MOST LIKELY FOCUS FOR THIS DURING THE LATE AFTERNOON OR
   EARLY EVENING...PARTICULARLY ACROSS PARTS OF NORTHWEST AND WEST
   CENTRAL TEXAS...WHERE IT APPEARS MID-LEVEL HEIGHT RISES COULD BE
   SUPPRESSED/SLOWED BY THE PROGRESSION OF A WEAK MID-LEVEL IMPULSE.

   ...SOUTHERN LOUISIANA...
   GUIDANCE SUGGESTS THAT FORCING ON THE NORTHEASTERN PERIPHERY OF THE
   BUILDING MID-LEVEL RIDGE COULD SUPPORT INCREASING STORM DEVELOPMENT
   BY MIDDAY...IN THE PRESENCE OF WEAK TO MODERATE BOUNDARY LAYER CAPE.
    LOW-LEVEL FLOW WILL BE WEAK...BUT 40-50 KT WEST NORTHWESTERLY 500
   MB FLOW WILL PROVIDE SUFFICIENT VERTICAL SHEAR FOR ORGANIZED STORM
   DEVELOPMENT...INCLUDING SUPERCELLS.

   ...SOUTHEAST FLORIDA...
   OUTPUT FROM THE NCEP SREF AND VARIOUS CONVECTION ALLOWING MODELS
   SUGGEST THE POTENTIAL FOR VIGOROUS STORM DEVELOPMENT THIS
   AFTERNOON...MAINLY NEAR COASTAL AREAS...ALONG THE SEA BREEZE.  IF
   THIS OCCURS...DEEP LAYER SHEAR AND INSTABILITY PROBABLY WILL BE
   SUFFICIENT FOR AN ISOLATED SUPERCELL OR TWO.

   ...CENTRAL HIGH PLAINS...
   A WEAK MID-LEVEL IMPULSE EMERGING FROM THE APPROACHING SOUTHERN
   BRANCH TROUGHING PROBABLY WILL AID CONVECTIVE DEVELOPMENT FROM THE
   FRONT RANGE OF THE ROCKIES NORTHWARD TOWARD THE BLACK HILLS BY LATE
   AFTERNOON.  LOW MOISTURE CONTENT APPEARS THE PRIMARY LIMITING FACTOR
   TO HIGHER SEVERE PROBABILITIES AT THE PRESENT TIME...AS LAPSE RATES
   ARE EXPECTED TO BE STEEP...AND VERTICAL SHEAR SHOULD BE AT LEAST
   MARGINALLY SUFFICIENT FOR ISOLATED SUPERCELLS.

Convective Outlooks

This is tomorrow's forecast for organized severe thunderstorms over the contiguous United States. Please read the description of the risk categories for further information. The latest Day 2 Outlook is available as well as all Outlooks that have been issued today.Tomorrow's Outlook
Current Day 2 Convective Outlook graphic and text
This is the day after tomorrow's (day 3) forecast for organized severe thunderstorms over the contiguous United States. Please read the description of the risk categories for further information. The latest Day 3 Outlook is available as well as all Outlooks that have been issued today.Day 3 Outlook
Current Day 3 Convective Outlook graphic
and text
This is the day 4-8 forecast for organized severe thunderstorms over the contiguous United States. The latest Day 4-8 Outlook is available as well as all Outlooks that have been issued today.Note: A severe weather area depicted in the Day 4-8 period indicates a 30% or higher probability for severe thunderstorms (e.g. a 30% chance that a severe thunderstorm will occur within 25 miles of any point).Day 4-8 Outlook
Current Day 4-8 Convective Outlook graphic
and text