jeudi 30 avril 2015
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
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.
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
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
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.
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.
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.
dimanche 26 avril 2015
4/26/2015 Ben McMillan Live Storm Chasing Feed from North Texas
https://www.youtube.com/watch?v=o4Qig_NS8rE
,,,,,,,,,,https://tvnweather.com/live
http://www.spc.noaa.gov/products/watch/
| Current Convective Watches (View What is a Watch? clip) Updated: Mon Apr 27 00:39:20 UTC 2015   |
http://www.spc.noaa.gov/products/md/
| Current Mesoscale Discussions Updated: Sun Apr 26 17:47:03 UTC 2015  |
| Mesoscale Discussion 466 | |
| < Previous MD | |
 | |
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 > | |
 | |
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. | |
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 | |
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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. | |
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
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.
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
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
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.
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 |
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| 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 |
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| 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 |
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