WTNT32 KNHC 290837
TCPAT2
BULLETIN
SUBTROPICAL STORM LAURA ADVISORY NUMBER 1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL122008
500 AM AST MON SEP 29 2008
...SUBTROPICAL STORM LAURA FORMS OVER THE NORTH CENTRAL ATLANTIC...
AT 500 AM AST...0900Z...THE CENTER OF SUBTROPICAL STORM LAURA WAS
LOCATED NEAR LATITUDE 37.2 NORTH...LONGITUDE 47.3 WEST OR ABOUT 1015
MILES...1635 KM...WEST OF FAYAL ISLAND IN THE WESTERN AZORES.
THE STORM IS MOVING TOWARD THE WEST-NORTHWEST NEAR 8 MPH. A GRADUAL
TURN TOWARD THE NORTHWEST AND NORTH ACCOMPANIED BY AN INCREASE IN
FORWARD SPEED IS EXPECTED ON TUESDAY. LAURA IS NOT FORECAST TO
AFFECT ANY LAND AREAS...AND THE SYSTEM IS ONLY A THREAT TO SHIPPING
INTERESTS OVER THE FAR NORTH ATLANTIC OCEAN.
MAXIMUM SUSTAINED WINDS ARE NEAR 60 MPH...95 KM/HR...WITH HIGHER
GUSTS. SOME STRENGTHENING IS FORECAST DURING THE NEXT 24 HOURS...
AND LAURA COULD TRANSITION INTO A TROPICAL CYCLONE LATER TODAY AND
POSSIBLY BECOME A HURRICANE BY TUESDAY.
WINDS OF 40 MPH EXTEND OUTWARD UP TO 310 MILES...500 KM FROM THE
CENTER.
THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 993 MB...29.32 INCHES.
REPEATING THE 500 AM AST POSITION...37.2 N...47.3 W. MOVEMENT
TOWARD...WEST-NORTHWEST NEAR 8 MPH. MAXIMUM SUSTAINED WINDS...60
MPH. MINIMUM CENTRAL PRESSURE...993 MB.
THE NEXT ADVISORY WILL BE ISSUED BY THE NATIONAL HURRICANE CENTER AT
1100 AM AST.
$$
FORECASTER STEWART
ATL LAURA: Advisories
Moderator: S2k Moderators
ATL LAURA: Advisories
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WTNT42 KNHC 290840
TCDAT2
SUBTROPICAL STORM LAURA DISCUSSION NUMBER 1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL122008
500 AM EDT MON SEP 29 2008
DURING THE PAST 6 HOURS...CONVENTIONAL SATELLITE IMAGERY INDICATES
DEEP CONVECTION WITH CLOUD TOPS TO NEAR -70C HAS CONTINUED TO
INCREASE AND HAS STARTED WRAPPING AROUND AND VERY NEAR THE CENTER
OF THE LARGE NON-TROPICAL LOW PRESSURE SYSTEM LOCATED ABOUT 775 NMI
WEST OF THE WESTERNMOST AZORES ISLANDS. THERE IS ENOUGH CONVECTION
NEAR THE CENTER NOW FOR THIS SYSTEM TO BE CLASSIFIED AS A
SUBTROPICAL STORM. THE 06Z SATELLITE CLASSIFICATION FROM TAFB WAS
ST3.0/45 KT...BUT USING THE DVORAK TECHNIQUE FOR A TROPICAL SYSTEM
YIELDS NEARLY EIGHT TENTHS BANDING...OR T3.5/55 KT. SO THE INITIAL
INTENSITY IS BEING SET AT 50 KT...WHICH IS CONSISTENT WITH A FEW
50-KT WIND VECTORS NOTED IN THE NORTHWEST QUADRANT IN A 28/2133Z
QUIKSCAT HI-RES OVERPASS. HOWEVER...SINCE THE TIME OF THAT
OVERPASS... CONVECTION HAS INCREASED MARKEDLY AND IS NOW THE SOLID
BAND OF CONVECTION IN THE SOUTHERN SEMICIRCLE. THEREFORE...IT IS
POSSIBLE THAT THE INITIAL INTENSITY COULD BE A LITTLE HIGHER THAN
CURRENTLY INDICATED.
THE INITIAL MOTION ESTIMATE IS 285/7. ALL OF THE NHC MODEL GUIDANCE
IS IN GOOD AGREEMENT ON SUBTROPICAL STORM LAURA MOVING TO THE
WEST-NORTHWEST FOR THE NEXT 12 HOURS OR SO...AND THEN TURNING
TOWARD THE NORTHWEST AND NORTH AND ACCELERATING AS THE INCIPIENT
MID-LEVEL CIRCULATION WEAKENS AND OPENS UP INTO A TROUGH AND GETS
LIFTED NORTHWARD AROUND THE WESTERN PERIPHERY OF A NORTH-SOUTH
ORIENTED MID-LEVEL RIDGE ANCHORED OVER THE AZORES ISLANDS. AFTER
REACHING THE HIGHER LATITUDES IN ABOUT 72 HOURS...LAURA IS FORECAST
TO GET PICKED BY THE FAST WESTERLIES AND MOVE QUICKLY EASTWARD AS
AN EXTRATROPICAL STORM SYSTEM.
LAURA IS EXPECTED TO REMAIN OVER 25C-26C SSTS FOR THE NEXT 24 HOURS
AND ALSO BE UNDER LIGHT TO MODERATE SHEAR CONDITIONS. THEREFORE...
SOME ADDITIONAL STRENGTHENING IS FORECAST. HOWEVER...IF THE CURRENT
TREND OF CONVECTION WRAPPING AROUND THE CENTER CONTINUES...THEN
SUBTROPICAL STORM LAURA COULD QUICKLY TRANSITION OVER TO A TROPICAL
CYCLONE AND BECOME A HURRICANE WITH A BANDING EYE FEATURE LATER
TODAY. BY 36 HOURS...LAURA IS EXPECTED TO BE MOVING OVER MUCH
COOLER WATER...WHICH SHOULD INDUCE WEAKENING ALONG WITH A GRADUAL
TRANSITION TO EXTRATROPICAL STATUS. THE OFFICIAL INTENSITY FORECAST
IS A BLEND OF THE SHIPS...GFDL...HWRF...AND ICON INTENSITY MODELS.
FORECAST POSITIONS AND MAX WINDS
INITIAL 29/0900Z 37.2N 47.3W 50 KT
12HR VT 29/1800Z 38.0N 48.3W 55 KT
24HR VT 30/0600Z 39.8N 48.9W 60 KT
36HR VT 30/1800Z 41.7N 48.8W 60 KT...BECOMING EXTRATROPICAL
48HR VT 01/0600Z 44.0N 48.0W 55 KT...EXTRATROPICAL
72HR VT 02/0600Z 51.5N 44.0W 50 KT...EXTRATROPICAL
96HR VT 03/0600Z 58.0N 34.5W 45 KT...EXTRATROPICAL
120HR VT 04/0600Z 57.0N 21.5W 40 KT...EXTRATROPICAL
$$
FORECASTER STEWART
TCDAT2
SUBTROPICAL STORM LAURA DISCUSSION NUMBER 1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL122008
500 AM EDT MON SEP 29 2008
DURING THE PAST 6 HOURS...CONVENTIONAL SATELLITE IMAGERY INDICATES
DEEP CONVECTION WITH CLOUD TOPS TO NEAR -70C HAS CONTINUED TO
INCREASE AND HAS STARTED WRAPPING AROUND AND VERY NEAR THE CENTER
OF THE LARGE NON-TROPICAL LOW PRESSURE SYSTEM LOCATED ABOUT 775 NMI
WEST OF THE WESTERNMOST AZORES ISLANDS. THERE IS ENOUGH CONVECTION
NEAR THE CENTER NOW FOR THIS SYSTEM TO BE CLASSIFIED AS A
SUBTROPICAL STORM. THE 06Z SATELLITE CLASSIFICATION FROM TAFB WAS
ST3.0/45 KT...BUT USING THE DVORAK TECHNIQUE FOR A TROPICAL SYSTEM
YIELDS NEARLY EIGHT TENTHS BANDING...OR T3.5/55 KT. SO THE INITIAL
INTENSITY IS BEING SET AT 50 KT...WHICH IS CONSISTENT WITH A FEW
50-KT WIND VECTORS NOTED IN THE NORTHWEST QUADRANT IN A 28/2133Z
QUIKSCAT HI-RES OVERPASS. HOWEVER...SINCE THE TIME OF THAT
OVERPASS... CONVECTION HAS INCREASED MARKEDLY AND IS NOW THE SOLID
BAND OF CONVECTION IN THE SOUTHERN SEMICIRCLE. THEREFORE...IT IS
POSSIBLE THAT THE INITIAL INTENSITY COULD BE A LITTLE HIGHER THAN
CURRENTLY INDICATED.
THE INITIAL MOTION ESTIMATE IS 285/7. ALL OF THE NHC MODEL GUIDANCE
IS IN GOOD AGREEMENT ON SUBTROPICAL STORM LAURA MOVING TO THE
WEST-NORTHWEST FOR THE NEXT 12 HOURS OR SO...AND THEN TURNING
TOWARD THE NORTHWEST AND NORTH AND ACCELERATING AS THE INCIPIENT
MID-LEVEL CIRCULATION WEAKENS AND OPENS UP INTO A TROUGH AND GETS
LIFTED NORTHWARD AROUND THE WESTERN PERIPHERY OF A NORTH-SOUTH
ORIENTED MID-LEVEL RIDGE ANCHORED OVER THE AZORES ISLANDS. AFTER
REACHING THE HIGHER LATITUDES IN ABOUT 72 HOURS...LAURA IS FORECAST
TO GET PICKED BY THE FAST WESTERLIES AND MOVE QUICKLY EASTWARD AS
AN EXTRATROPICAL STORM SYSTEM.
LAURA IS EXPECTED TO REMAIN OVER 25C-26C SSTS FOR THE NEXT 24 HOURS
AND ALSO BE UNDER LIGHT TO MODERATE SHEAR CONDITIONS. THEREFORE...
SOME ADDITIONAL STRENGTHENING IS FORECAST. HOWEVER...IF THE CURRENT
TREND OF CONVECTION WRAPPING AROUND THE CENTER CONTINUES...THEN
SUBTROPICAL STORM LAURA COULD QUICKLY TRANSITION OVER TO A TROPICAL
CYCLONE AND BECOME A HURRICANE WITH A BANDING EYE FEATURE LATER
TODAY. BY 36 HOURS...LAURA IS EXPECTED TO BE MOVING OVER MUCH
COOLER WATER...WHICH SHOULD INDUCE WEAKENING ALONG WITH A GRADUAL
TRANSITION TO EXTRATROPICAL STATUS. THE OFFICIAL INTENSITY FORECAST
IS A BLEND OF THE SHIPS...GFDL...HWRF...AND ICON INTENSITY MODELS.
FORECAST POSITIONS AND MAX WINDS
INITIAL 29/0900Z 37.2N 47.3W 50 KT
12HR VT 29/1800Z 38.0N 48.3W 55 KT
24HR VT 30/0600Z 39.8N 48.9W 60 KT
36HR VT 30/1800Z 41.7N 48.8W 60 KT...BECOMING EXTRATROPICAL
48HR VT 01/0600Z 44.0N 48.0W 55 KT...EXTRATROPICAL
72HR VT 02/0600Z 51.5N 44.0W 50 KT...EXTRATROPICAL
96HR VT 03/0600Z 58.0N 34.5W 45 KT...EXTRATROPICAL
120HR VT 04/0600Z 57.0N 21.5W 40 KT...EXTRATROPICAL
$$
FORECASTER STEWART
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cycloneye
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Re: ATL: LAURA - Subtropical Storm: Advisories
WTNT22 KNHC 291438
TCMAT2
SUBTROPICAL STORM LAURA FORECAST/ADVISORY NUMBER 2
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL122008
1500 UTC MON SEP 29 2008
SUBTROPICAL STORM CENTER LOCATED NEAR 37.4N 47.8W AT 29/1500Z
POSITION ACCURATE WITHIN 20 NM
PRESENT MOVEMENT TOWARD THE WEST-NORTHWEST OR 300 DEGREES AT 7 KT
ESTIMATED MINIMUM CENTRAL PRESSURE 995 MB
MAX SUSTAINED WINDS 50 KT WITH GUSTS TO 60 KT.
50 KT....... 80NE 100SE 0SW 0NW.
34 KT.......240NE 200SE 150SW 180NW.
12 FT SEAS..360NE 360SE 360SW 360NW.
WINDS AND SEAS VARY GREATLY IN EACH QUADRANT. RADII IN NAUTICAL
MILES ARE THE LARGEST RADII EXPECTED ANYWHERE IN THAT QUADRANT.
REPEAT...CENTER LOCATED NEAR 37.4N 47.8W AT 29/1500Z
AT 29/1200Z CENTER WAS LOCATED NEAR 37.1N 47.6W
FORECAST VALID 30/0000Z 38.1N 48.3W
MAX WIND 55 KT...GUSTS 65 KT.
50 KT... 80NE 80SE 30SW 30NW.
34 KT...240NE 200SE 150SW 180NW.
FORECAST VALID 30/1200Z 39.8N 48.3W
MAX WIND 60 KT...GUSTS 75 KT.
50 KT... 90NE 90SE 45SW 45NW.
34 KT...240NE 200SE 150SW 180NW.
FORECAST VALID 01/0000Z 41.8N 47.7W
MAX WIND 60 KT...GUSTS 75 KT.
50 KT... 75NE 60SE 45SW 60NW.
34 KT...240NE 200SE 150SW 180NW.
FORECAST VALID 01/1200Z 44.4N 46.6W...EXTRATROPICAL
MAX WIND 55 KT...GUSTS 65 KT.
50 KT... 75NE 75SE 75SW 60NW.
34 KT...200NE 200SE 150SW 120NW.
FORECAST VALID 02/1200Z 51.5N 41.5W...EXTRATROPICAL
MAX WIND 50 KT...GUSTS 60 KT.
50 KT... 75NE 75SE 75SW 60NW.
34 KT...200NE 200SE 150SW 120NW.
EXTENDED OUTLOOK. NOTE...ERRORS FOR TRACK HAVE AVERAGED NEAR 225 NM
ON DAY 4 AND 300 NM ON DAY 5...AND FOR INTENSITY NEAR 20 KT EACH DAY
OUTLOOK VALID 03/1200Z 55.5N 30.5W...EXTRATROPICAL
MAX WIND 45 KT...GUSTS 55 KT.
OUTLOOK VALID 04/1200Z 55.0N 15.0W...EXTRATROPICAL
MAX WIND 45 KT...GUSTS 55 KT.
REQUEST FOR 3 HOURLY SHIP REPORTS WITHIN 300 MILES OF 37.4N 47.8W
NEXT ADVISORY AT 29/2100Z
$$
FORECASTER BERG/PASCH
WTNT42 KNHC 291439
TCDAT2
SUBTROPICAL STORM LAURA DISCUSSION NUMBER 2
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL122008
1100 AM EDT MON SEP 29 2008
AN 0852 UTC QUIKSCAT PASS OVER LAURA CONFIRMED THAT THE MAXIMUM
WINDS ARE NEAR 50 KT WITHIN A SWATH LOCATED ABOUT 75 NM EAST OF THE
CENTER. SUBTROPICAL CLASSIFICATIONS OF ST3.0 FROM TAFB AND SAB
ALSO SUPPORT THIS INITIAL INTENSITY. A PRONOUNCED CONVECTIVE BAND
NOW CURLS ABOUT THREE QUARTERS OF THE WAY AROUND THE EAST AND NORTH
OF THE LARGE CIRCULATION BUT THE LOW-LEVEL CENTER REMAINS BROAD AND
ILL-DEFINED WITH SEVERAL INTERNAL SMALLER SWIRLS. WITH THE
IMPROVED CONVECTIVE SIGNATURE...A CASE COULD BE MADE THAT THE
CYCLONE IS BEGINNING TO ACQUIRE MORE TROPICAL CHARACTERISTICS.
LAURA IS BEGINNING TO MAKE A MORE PRONOUNCED POLEWARD TURN AS IT
MOVES BETWEEN HIGH PRESSURE NORTH OF THE AZORES AND THE
EXTRATROPICAL REMNANTS OF HURRICANE KYLE OVER THE CANADIAN
MARITIMES. A NORTHWESTWARD TO NORTHWARD MOTION WILL CONTINUE FOR
THE NEXT 36 HOURS OR SO BUT THE LATEST TRACK GUIDANCE HAS SHIFTED
TO THE RIGHT OF THE PREVIOUS OFFICIAL FORECAST. THE NEW FORECAST
DOES NOT GO AS FAR TO THE RIGHT AS THE MODEL CONSENSUS AND INSTEAD
LIES ON THE LEFT SIDE OF THE GUIDANCE...CLOSE TO THE GFS AND
GFDL. LAURA WILL LIKELY BE PICKED UP BY THE MID-LATITUDE TROUGH
CURRENTLY OVER THE CANADIAN MARITIMES BY DAY 3 AND THEN ACCELERATE
EASTWARD WITHIN THE MID-LATITUDE FLOW...POSSIBLY APPROACHING THE
BRITISH ISLES AS A POWERFUL EXTRATROPICAL LOW.
OCEAN WATERS ARE MARGINALLY WARM NEAR LAURA...BUT APPEAR TO BE JUST
WARM ENOUGH TO SUPPORT INCREASED CONVECTION. IF THE CONVECTION CAN
WRAP CLOSER TO THE CENTER...THERE IS A CHANCE THAT THE CYCLONE
COULD BECOME A TROPICAL CYCLONE BEFORE TRANSITIONING INTO AN
EXTRATROPICAL LOW. THEREFORE...SOME STRENGTHENING IS INDICATED
OVER THE NEXT 24 HOURS JUST BEFORE LAURA MOVES OVER INCREASINGLY
LOWER SEA SURFACE TEMPERATURES. MOST OF THE DYNAMICAL GUIDANCE IS
RATHER UNIMPRESSED WITH THE POTENTIAL FOR INTENSIFICATION WHEREAS
THE SHIPS MODEL SHOWS LAURA STRENGTHENING TO 80 KT BY DAY 4 OR
5...PRIMARILY DUE TO A STRONG CONTRIBUTION FROM COLD UPPER LEVEL
TEMPERATURES.
FORECAST POSITIONS AND MAX WINDS
INITIAL 29/1500Z 37.4N 47.8W 50 KT
12HR VT 30/0000Z 38.1N 48.3W 55 KT
24HR VT 30/1200Z 39.8N 48.3W 60 KT
36HR VT 01/0000Z 41.8N 47.7W 60 KT
48HR VT 01/1200Z 44.4N 46.6W 55 KT...EXTRATROPICAL
72HR VT 02/1200Z 51.5N 41.5W 50 KT...EXTRATROPICAL
96HR VT 03/1200Z 55.5N 30.5W 45 KT...EXTRATROPICAL
120HR VT 04/1200Z 55.0N 15.0W 45 KT...EXTRATROPICAL
$$
FORECASTER BERG/PASCH
TCMAT2
SUBTROPICAL STORM LAURA FORECAST/ADVISORY NUMBER 2
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL122008
1500 UTC MON SEP 29 2008
SUBTROPICAL STORM CENTER LOCATED NEAR 37.4N 47.8W AT 29/1500Z
POSITION ACCURATE WITHIN 20 NM
PRESENT MOVEMENT TOWARD THE WEST-NORTHWEST OR 300 DEGREES AT 7 KT
ESTIMATED MINIMUM CENTRAL PRESSURE 995 MB
MAX SUSTAINED WINDS 50 KT WITH GUSTS TO 60 KT.
50 KT....... 80NE 100SE 0SW 0NW.
34 KT.......240NE 200SE 150SW 180NW.
12 FT SEAS..360NE 360SE 360SW 360NW.
WINDS AND SEAS VARY GREATLY IN EACH QUADRANT. RADII IN NAUTICAL
MILES ARE THE LARGEST RADII EXPECTED ANYWHERE IN THAT QUADRANT.
REPEAT...CENTER LOCATED NEAR 37.4N 47.8W AT 29/1500Z
AT 29/1200Z CENTER WAS LOCATED NEAR 37.1N 47.6W
FORECAST VALID 30/0000Z 38.1N 48.3W
MAX WIND 55 KT...GUSTS 65 KT.
50 KT... 80NE 80SE 30SW 30NW.
34 KT...240NE 200SE 150SW 180NW.
FORECAST VALID 30/1200Z 39.8N 48.3W
MAX WIND 60 KT...GUSTS 75 KT.
50 KT... 90NE 90SE 45SW 45NW.
34 KT...240NE 200SE 150SW 180NW.
FORECAST VALID 01/0000Z 41.8N 47.7W
MAX WIND 60 KT...GUSTS 75 KT.
50 KT... 75NE 60SE 45SW 60NW.
34 KT...240NE 200SE 150SW 180NW.
FORECAST VALID 01/1200Z 44.4N 46.6W...EXTRATROPICAL
MAX WIND 55 KT...GUSTS 65 KT.
50 KT... 75NE 75SE 75SW 60NW.
34 KT...200NE 200SE 150SW 120NW.
FORECAST VALID 02/1200Z 51.5N 41.5W...EXTRATROPICAL
MAX WIND 50 KT...GUSTS 60 KT.
50 KT... 75NE 75SE 75SW 60NW.
34 KT...200NE 200SE 150SW 120NW.
EXTENDED OUTLOOK. NOTE...ERRORS FOR TRACK HAVE AVERAGED NEAR 225 NM
ON DAY 4 AND 300 NM ON DAY 5...AND FOR INTENSITY NEAR 20 KT EACH DAY
OUTLOOK VALID 03/1200Z 55.5N 30.5W...EXTRATROPICAL
MAX WIND 45 KT...GUSTS 55 KT.
OUTLOOK VALID 04/1200Z 55.0N 15.0W...EXTRATROPICAL
MAX WIND 45 KT...GUSTS 55 KT.
REQUEST FOR 3 HOURLY SHIP REPORTS WITHIN 300 MILES OF 37.4N 47.8W
NEXT ADVISORY AT 29/2100Z
$$
FORECASTER BERG/PASCH
WTNT42 KNHC 291439
TCDAT2
SUBTROPICAL STORM LAURA DISCUSSION NUMBER 2
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL122008
1100 AM EDT MON SEP 29 2008
AN 0852 UTC QUIKSCAT PASS OVER LAURA CONFIRMED THAT THE MAXIMUM
WINDS ARE NEAR 50 KT WITHIN A SWATH LOCATED ABOUT 75 NM EAST OF THE
CENTER. SUBTROPICAL CLASSIFICATIONS OF ST3.0 FROM TAFB AND SAB
ALSO SUPPORT THIS INITIAL INTENSITY. A PRONOUNCED CONVECTIVE BAND
NOW CURLS ABOUT THREE QUARTERS OF THE WAY AROUND THE EAST AND NORTH
OF THE LARGE CIRCULATION BUT THE LOW-LEVEL CENTER REMAINS BROAD AND
ILL-DEFINED WITH SEVERAL INTERNAL SMALLER SWIRLS. WITH THE
IMPROVED CONVECTIVE SIGNATURE...A CASE COULD BE MADE THAT THE
CYCLONE IS BEGINNING TO ACQUIRE MORE TROPICAL CHARACTERISTICS.
LAURA IS BEGINNING TO MAKE A MORE PRONOUNCED POLEWARD TURN AS IT
MOVES BETWEEN HIGH PRESSURE NORTH OF THE AZORES AND THE
EXTRATROPICAL REMNANTS OF HURRICANE KYLE OVER THE CANADIAN
MARITIMES. A NORTHWESTWARD TO NORTHWARD MOTION WILL CONTINUE FOR
THE NEXT 36 HOURS OR SO BUT THE LATEST TRACK GUIDANCE HAS SHIFTED
TO THE RIGHT OF THE PREVIOUS OFFICIAL FORECAST. THE NEW FORECAST
DOES NOT GO AS FAR TO THE RIGHT AS THE MODEL CONSENSUS AND INSTEAD
LIES ON THE LEFT SIDE OF THE GUIDANCE...CLOSE TO THE GFS AND
GFDL. LAURA WILL LIKELY BE PICKED UP BY THE MID-LATITUDE TROUGH
CURRENTLY OVER THE CANADIAN MARITIMES BY DAY 3 AND THEN ACCELERATE
EASTWARD WITHIN THE MID-LATITUDE FLOW...POSSIBLY APPROACHING THE
BRITISH ISLES AS A POWERFUL EXTRATROPICAL LOW.
OCEAN WATERS ARE MARGINALLY WARM NEAR LAURA...BUT APPEAR TO BE JUST
WARM ENOUGH TO SUPPORT INCREASED CONVECTION. IF THE CONVECTION CAN
WRAP CLOSER TO THE CENTER...THERE IS A CHANCE THAT THE CYCLONE
COULD BECOME A TROPICAL CYCLONE BEFORE TRANSITIONING INTO AN
EXTRATROPICAL LOW. THEREFORE...SOME STRENGTHENING IS INDICATED
OVER THE NEXT 24 HOURS JUST BEFORE LAURA MOVES OVER INCREASINGLY
LOWER SEA SURFACE TEMPERATURES. MOST OF THE DYNAMICAL GUIDANCE IS
RATHER UNIMPRESSED WITH THE POTENTIAL FOR INTENSIFICATION WHEREAS
THE SHIPS MODEL SHOWS LAURA STRENGTHENING TO 80 KT BY DAY 4 OR
5...PRIMARILY DUE TO A STRONG CONTRIBUTION FROM COLD UPPER LEVEL
TEMPERATURES.
FORECAST POSITIONS AND MAX WINDS
INITIAL 29/1500Z 37.4N 47.8W 50 KT
12HR VT 30/0000Z 38.1N 48.3W 55 KT
24HR VT 30/1200Z 39.8N 48.3W 60 KT
36HR VT 01/0000Z 41.8N 47.7W 60 KT
48HR VT 01/1200Z 44.4N 46.6W 55 KT...EXTRATROPICAL
72HR VT 02/1200Z 51.5N 41.5W 50 KT...EXTRATROPICAL
96HR VT 03/1200Z 55.5N 30.5W 45 KT...EXTRATROPICAL
120HR VT 04/1200Z 55.0N 15.0W 45 KT...EXTRATROPICAL
$$
FORECASTER BERG/PASCH
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cycloneye
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Re: ATL: LAURA - Subtropical Storm: Advisories
WTNT42 KNHC 292032
TCDAT2
SUBTROPICAL STORM LAURA DISCUSSION NUMBER 3
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL122008
500 PM EDT MON SEP 29 2008
AN ASCAT PASS AROUND 1326 UTC THIS MORNING INDICATED MAXIMUM WINDS
NEAR 45 KT...BUT THIS SENSOR USUALLY TENDS TO HAVE A SLIGHT LOW
BIAS SO AN INTENSITY OF 50 KT WILL BE MAINTAINED IN THIS PACKAGE.
LAURA CONTINUES TO ACQUIRE SOME TROPICAL CHARACTERISTICS...WITH THE
FSU PHASE SPACE DIAGRAMS AND AMSU DATA BOTH INDICATING A DEEP WARM
CORE. ON THE OTHER HAND...THE ASSOCIATED CONVECTION IS NOT ALL
THAT DEEP AND THE 75 NM RADIUS OF MAXIMUM WINDS IS IN THE GRAY ZONE
BETWEEN TROPICAL AND SUBTROPICAL. LAURA WILL CONTINUE TO BE
CLASSIFIED AS A SUBTROPICAL STORM FOR NOW ALTHOUGH THE TRANSITION
TO A TROPICAL CYCLONE IS LIKELY OCCURRING.
LATEST SATELLITE FIXES INDICATE THAT LAURA IS TURNING AND
ACCELERATING WITH AN INITIAL MOTION OF 335/8. THE TRACK FORECAST
REASONING HAS NOT CHANGED. ALTHOUGH SOME OF THE MODELS...INCLUDING
THE GFS...GFDL...AND ECMWF...HAVE SHIFTED LEFT SINCE THIS
MORNING...THE OFFICIAL FORECAST LIES VERY CLOSE TO THE MODEL
CONSENSUS AND IS NOT FAR FROM THE PREVIOUS FORECAST.
IF LAURA IS BECOMING MORE TROPICAL...IT HAS A CHANCE TO STRENGTHEN A
LITTLE BEFORE IT MOVES OVER COLDER WATERS. THE OFFICIAL FORECAST
FOLLOWS CLOSE TO THE SHIPS AND LGEM MODELS FOR THE FIRST 36 HOURS
BUT THEN CALLS FOR GRADUAL WEAKENING ONCE LAURA BECOMES
EXTRATROPICAL AND MOVES INTO A COLDER AIR MASS...MUCH LIKE AN
OCCLUDED LOW. THE OFFICIAL FORECAST IS IN BEST AGREEMENT WITH THE
GFDL AND HWRF GUIDANCE. LAURA WILL BEGIN EXTRATROPICAL TRANSITION
BY 36 HOURS AND THEN COULD BE FULLY ABSORBED INTO A FRONTAL ZONE BY
DAY 5 WEST OF IRELAND...ALTHOUGH A POINT AT THAT TIME IS STILL
GIVEN FOR CONTINUITY.
FORECAST POSITIONS AND MAX WINDS
INITIAL 29/2100Z 38.3N 48.4W 50 KT
12HR VT 30/0600Z 39.3N 48.6W 55 KT
24HR VT 30/1800Z 41.2N 48.3W 60 KT
36HR VT 01/0600Z 43.6N 47.4W 55 KT
48HR VT 01/1800Z 46.5N 46.0W 50 KT...EXTRATROPICAL
72HR VT 02/1800Z 52.5N 41.0W 50 KT...EXTRATROPICAL
96HR VT 03/1800Z 55.0N 28.0W 45 KT...EXTRATROPICAL
120HR VT 04/1800Z 55.0N 12.0W 45 KT...EXTRATROPICAL
$$
FORECASTER BERG/FRANKLIN
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cycloneye
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Re: ATL: LAURA - Subtropical Storm: Advisories
WTNT42 KNHC 300234
TCDAT2
SUBTROPICAL STORM LAURA DISCUSSION NUMBER 4
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL122008
1100 PM EDT MON SEP 29 2008
OVERALL THE CONVECTIVE CLOUD TOPS HAVE WARMED A LITTLE OVER THE PAST
SEVERAL HOURS...AND THE SATELLITE CLASSIFICATIONS FROM BOTH TAFB
AND SAB ARE BELOW THEIR EARLIER PEAKS. INDEED...THE DEEP
CONVECTION IS QUITE PALTRY AT THIS TIME. HOWEVER...A QUIKSCAT PASS
FROM 21Z CAUGHT THE EASTERN HALF OF THE CIRCULATION...AND THESE
DATA STILL SUPPORT 45-50 KT...SO THE ADVISORY INTENSITY IS
UNCHANGED. EVEN THOUGH THE RADIUS OF MAXIMUM WINDS IS AROUND 70 N
MI...SMALLER THAN FOR MANY SUBTROPICAL CYCLONES... LAURA IS STILL
VERY MUCH INVOLVED WITH AN UPPER-LOW...WHICH IS A DEFINING
CHARACTERISTIC OF A SUBTROPICAL STORM. I'M NOT INCLINED TO CALL
THIS THING FULLY TROPICAL UNTIL IT DOES A BETTER JOB OF ERODING THE
UPPER LOW. OVER THE NEXT DAY OR SO THE UPPER-LOW IS EXPECTED TO
WEAKEN AS LAURA MOVES INTO THE WESTERLIES...AND LAURA STILL COULD
BECOME A TROPICAL CYCLONE BEFORE SEA SURFACE TEMPERATURES DROP
DRAMATICALLY ALONG THE FORECAST TRACK IN ABOUT 18 HOURS. WEAKENING
IS EXPECTED ONCE THAT HAPPENS...ALTHOUGH BOTH THE GFS AND THE ECMWF
SUGGEST THAT LAURA COULD INTENSIFY AND EXPAND AS AN EXTRATROPICAL
LOW. BASED ON THIS LATTER GUIDANCE...THE FORECAST WIND RADII HAVE
BEEN EXPANDED AT 48 AND 72 HOURS.
LAURA IS MOVING SLOWLY NORTHWARD...360/8...BETWEEN A LARGE AREA OF
HIGH PRESSURE OVER THE AZORES AND A MID- TO UPPER-LEVEL TROUGH OVER
EASTERN CANADA THAT CONTAINS THE REMNANTS OF KYLE. MODEL GUIDANCE
IS IN GOOD AGREEMENT THAT LAURA WILL CONTINUE NORTHWARD BETWEEN
THESE FEATURES AND ENTER THE WESTERLIES IN ABOUT THREE DAYS. THE
OFFICIAL FORECAST IS NEAR THE DYNAMICAL MODEL CONSENSUS AND A
LITTLE LEFT OF AND SLOWER THAN THE PREVIOUS ADVISORY.
FORECAST POSITIONS AND MAX WINDS
INITIAL 30/0300Z 39.0N 48.4W 50 KT
12HR VT 30/1200Z 40.3N 48.4W 55 KT
24HR VT 01/0000Z 42.6N 47.9W 50 KT
36HR VT 01/1200Z 45.3N 46.8W 45 KT...EXTRATROPICAL
48HR VT 02/0000Z 48.5N 45.5W 40 KT...EXTRATROPICAL
72HR VT 03/0000Z 53.5N 39.0W 45 KT...EXTRATROPICAL
96HR VT 04/0000Z 55.0N 27.0W 50 KT...EXTRATROPICAL
120HR VT 05/0000Z 55.0N 13.0W 55 KT...EXTRATROPICAL
$$
FORECASTER FRANKLIN
TCDAT2
SUBTROPICAL STORM LAURA DISCUSSION NUMBER 4
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL122008
1100 PM EDT MON SEP 29 2008
OVERALL THE CONVECTIVE CLOUD TOPS HAVE WARMED A LITTLE OVER THE PAST
SEVERAL HOURS...AND THE SATELLITE CLASSIFICATIONS FROM BOTH TAFB
AND SAB ARE BELOW THEIR EARLIER PEAKS. INDEED...THE DEEP
CONVECTION IS QUITE PALTRY AT THIS TIME. HOWEVER...A QUIKSCAT PASS
FROM 21Z CAUGHT THE EASTERN HALF OF THE CIRCULATION...AND THESE
DATA STILL SUPPORT 45-50 KT...SO THE ADVISORY INTENSITY IS
UNCHANGED. EVEN THOUGH THE RADIUS OF MAXIMUM WINDS IS AROUND 70 N
MI...SMALLER THAN FOR MANY SUBTROPICAL CYCLONES... LAURA IS STILL
VERY MUCH INVOLVED WITH AN UPPER-LOW...WHICH IS A DEFINING
CHARACTERISTIC OF A SUBTROPICAL STORM. I'M NOT INCLINED TO CALL
THIS THING FULLY TROPICAL UNTIL IT DOES A BETTER JOB OF ERODING THE
UPPER LOW. OVER THE NEXT DAY OR SO THE UPPER-LOW IS EXPECTED TO
WEAKEN AS LAURA MOVES INTO THE WESTERLIES...AND LAURA STILL COULD
BECOME A TROPICAL CYCLONE BEFORE SEA SURFACE TEMPERATURES DROP
DRAMATICALLY ALONG THE FORECAST TRACK IN ABOUT 18 HOURS. WEAKENING
IS EXPECTED ONCE THAT HAPPENS...ALTHOUGH BOTH THE GFS AND THE ECMWF
SUGGEST THAT LAURA COULD INTENSIFY AND EXPAND AS AN EXTRATROPICAL
LOW. BASED ON THIS LATTER GUIDANCE...THE FORECAST WIND RADII HAVE
BEEN EXPANDED AT 48 AND 72 HOURS.
LAURA IS MOVING SLOWLY NORTHWARD...360/8...BETWEEN A LARGE AREA OF
HIGH PRESSURE OVER THE AZORES AND A MID- TO UPPER-LEVEL TROUGH OVER
EASTERN CANADA THAT CONTAINS THE REMNANTS OF KYLE. MODEL GUIDANCE
IS IN GOOD AGREEMENT THAT LAURA WILL CONTINUE NORTHWARD BETWEEN
THESE FEATURES AND ENTER THE WESTERLIES IN ABOUT THREE DAYS. THE
OFFICIAL FORECAST IS NEAR THE DYNAMICAL MODEL CONSENSUS AND A
LITTLE LEFT OF AND SLOWER THAN THE PREVIOUS ADVISORY.
FORECAST POSITIONS AND MAX WINDS
INITIAL 30/0300Z 39.0N 48.4W 50 KT
12HR VT 30/1200Z 40.3N 48.4W 55 KT
24HR VT 01/0000Z 42.6N 47.9W 50 KT
36HR VT 01/1200Z 45.3N 46.8W 45 KT...EXTRATROPICAL
48HR VT 02/0000Z 48.5N 45.5W 40 KT...EXTRATROPICAL
72HR VT 03/0000Z 53.5N 39.0W 45 KT...EXTRATROPICAL
96HR VT 04/0000Z 55.0N 27.0W 50 KT...EXTRATROPICAL
120HR VT 05/0000Z 55.0N 13.0W 55 KT...EXTRATROPICAL
$$
FORECASTER FRANKLIN
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318
WTNT22 KNHC 301432
TCMAT2
TROPICAL STORM LAURA FORECAST/ADVISORY NUMBER 6
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL122008
1500 UTC TUE SEP 30 2008
TROPICAL STORM CENTER LOCATED NEAR 41.2N 48.8W AT 30/1500Z
POSITION ACCURATE WITHIN 20 NM
PRESENT MOVEMENT TOWARD THE NORTH OR 360 DEGREES AT 11 KT
ESTIMATED MINIMUM CENTRAL PRESSURE 996 MB
MAX SUSTAINED WINDS 50 KT WITH GUSTS TO 60 KT.
50 KT....... 60NE 0SE 0SW 0NW.
34 KT.......200NE 200SE 75SW 60NW.
12 FT SEAS..360NE 360SE 300SW 300NW.
WINDS AND SEAS VARY GREATLY IN EACH QUADRANT. RADII IN NAUTICAL
MILES ARE THE LARGEST RADII EXPECTED ANYWHERE IN THAT QUADRANT.
REPEAT...CENTER LOCATED NEAR 41.2N 48.8W AT 30/1500Z
AT 30/1200Z CENTER WAS LOCATED NEAR 40.6N 48.9W
FORECAST VALID 01/0000Z 42.8N 48.4W
MAX WIND 50 KT...GUSTS 60 KT.
50 KT... 60NE 0SE 0SW 0NW.
34 KT...180NE 150SE 75SW 60NW.
FORECAST VALID 01/1200Z 45.5N 47.4W...EXTRATROPICAL
MAX WIND 45 KT...GUSTS 55 KT.
34 KT...150NE 120SE 75SW 75NW.
FORECAST VALID 02/0000Z 48.7N 45.6W...EXTRATROPICAL
MAX WIND 40 KT...GUSTS 50 KT.
34 KT...150NE 120SE 75SW 75NW.
FORECAST VALID 02/1200Z 51.7N 43.6W...EXTRATROPICAL
MAX WIND 40 KT...GUSTS 50 KT.
34 KT...240NE 210SE 150SW 150NW.
FORECAST VALID 03/1200Z 56.0N 35.0W...EXTRATROPICAL
MAX WIND 45 KT...GUSTS 55 KT.
34 KT...375NE 325SE 200SW 350NW.
EXTENDED OUTLOOK. NOTE...ERRORS FOR TRACK HAVE AVERAGED NEAR 225 NM
ON DAY 4 AND 300 NM ON DAY 5...AND FOR INTENSITY NEAR 20 KT EACH DAY
OUTLOOK VALID 04/1200Z 57.0N 19.0W...EXTRATROPICAL
MAX WIND 50 KT...GUSTS 60 KT.
OUTLOOK VALID 05/1200Z 58.0N 3.5W...EXTRATROPICAL
MAX WIND 50 KT...GUSTS 60 KT.
REQUEST FOR 3 HOURLY SHIP REPORTS WITHIN 300 MILES OF 41.2N 48.8W
NEXT ADVISORY AT 30/2100Z
$$
FORECASTER BERG/PASCH
197
WTNT42 KNHC 301433
TCDAT2
TROPICAL STORM LAURA DISCUSSION NUMBER 6
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL122008
1100 AM EDT TUE SEP 30 2008
WHILE SOMEWHAT OF A PARADOX...LAURA CAN NOW BE DESIGNATED AS A
TROPICAL CYCLONE DESPITE THE FACT THAT IT CONTINUES TO MOVE
NORTHWARD OVER PROGRESSIVELY COLDER WATERS. THE ONE ASPECT WHICH
WAS HOLDING US BACK FROM DECLARING IT TROPICAL WAS THE UPPER LOW
COLLOCATED WITH THE SYSTEM. WATER VAPOR IMAGERY INDICATES THAT
THIS FEATURE HAS BECOME OFFSET AND STRETCHED TO THE SOUTHWEST OF
LAURA...AND UPPER LEVEL OUTFLOW IS NOW EXPANDING TO THE NORTH OF
THE CYCLONE. IN ADDITION...SCATTEROMETER DATA INDICATE THAT THE
RADIUS OF MAXIMUM WINDS HAS CONTINUED TO CONTRACT TO ABOUT 60 NM.
CLOUD TOP TEMPERATURES ARE NOT ALL THAT COLD...BUT THAT IS QUITE
NORMAL FOR HIGH-LATITUDE TROPICAL CYCLONES DUE TO THE LOWER
TROPOPAUSE. FRANKLY...LAURA NOW LOOKS LIKE A TROPICAL STORM.
THE INITIAL INTENSITY IS HELD AT 50 KT BASED ON AN 0827 UTC QUIKSCAT
PASS ALTHOUGH THE AREA OF STRONGEST WINDS HAS BEEN SHRINKING.
LAURA SHOULD BE ABLE TO HOLD THAT INTENSITY FOR ONLY ANOTHER 12
HOURS OR SO BEFORE MOVING OVER SEA SURFACE TEMPERATURES LESS THAN
18C. GLOBAL MODEL FIELDS INDICATE THAT THERMAL ADVECTION AROUND
THE SYSTEM BECOMES MORE PROMINENT LATER TONIGHT...AND LAURA IS
EXPECTED TO BE EXTRATROPICAL IN 24 HOURS OR SO AS IT MIGRATES INTO
THE COLDER AIR MASS. SOME GRADUAL WEAKENING THROUGH 48 HOURS IS
EXPECTED DUE TO THE COLDER OCEAN WATERS AND MARGINAL BAROCLINIC
FORCING. THEREAFTER...SOME RE-STRENGTHENING AND AN EXPANSION OF
THE WIND FIELD COULD OCCUR AS THE EXTRATROPICAL LOW RACES EAST
WITHIN THE MID-LATITUDE WESTERLIES TOWARDS THE NORTHERN BRITISH
ISLES. EXCEPT FOR A SLIGHT WESTWARD SHIFT IN THE TRACK GUIDANCE AT
36-48 HOURS...THERE HAS BEEN NO SIGNIFICANT CHANGE IN THE GLOBAL
MODELS FOR THIS CYCLE AND THE OFFICIAL FORECAST LIES VERY CLOSE TO
THE MODEL CONSENSUS.
FORECAST POSITIONS AND MAX WINDS
INITIAL 30/1500Z 41.2N 48.8W 50 KT
12HR VT 01/0000Z 42.8N 48.4W 50 KT
24HR VT 01/1200Z 45.5N 47.4W 45 KT...EXTRATROPICAL
36HR VT 02/0000Z 48.7N 45.6W 40 KT...EXTRATROPICAL
48HR VT 02/1200Z 51.7N 43.6W 40 KT...EXTRATROPICAL
72HR VT 03/1200Z 56.0N 35.0W 45 KT...EXTRATROPICAL
96HR VT 04/1200Z 57.0N 19.0W 50 KT...EXTRATROPICAL
120HR VT 05/1200Z 58.0N 3.5W 50 KT...EXTRATROPICAL
$$
FORECASTER BERG/PASCH
WTNT22 KNHC 301432
TCMAT2
TROPICAL STORM LAURA FORECAST/ADVISORY NUMBER 6
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL122008
1500 UTC TUE SEP 30 2008
TROPICAL STORM CENTER LOCATED NEAR 41.2N 48.8W AT 30/1500Z
POSITION ACCURATE WITHIN 20 NM
PRESENT MOVEMENT TOWARD THE NORTH OR 360 DEGREES AT 11 KT
ESTIMATED MINIMUM CENTRAL PRESSURE 996 MB
MAX SUSTAINED WINDS 50 KT WITH GUSTS TO 60 KT.
50 KT....... 60NE 0SE 0SW 0NW.
34 KT.......200NE 200SE 75SW 60NW.
12 FT SEAS..360NE 360SE 300SW 300NW.
WINDS AND SEAS VARY GREATLY IN EACH QUADRANT. RADII IN NAUTICAL
MILES ARE THE LARGEST RADII EXPECTED ANYWHERE IN THAT QUADRANT.
REPEAT...CENTER LOCATED NEAR 41.2N 48.8W AT 30/1500Z
AT 30/1200Z CENTER WAS LOCATED NEAR 40.6N 48.9W
FORECAST VALID 01/0000Z 42.8N 48.4W
MAX WIND 50 KT...GUSTS 60 KT.
50 KT... 60NE 0SE 0SW 0NW.
34 KT...180NE 150SE 75SW 60NW.
FORECAST VALID 01/1200Z 45.5N 47.4W...EXTRATROPICAL
MAX WIND 45 KT...GUSTS 55 KT.
34 KT...150NE 120SE 75SW 75NW.
FORECAST VALID 02/0000Z 48.7N 45.6W...EXTRATROPICAL
MAX WIND 40 KT...GUSTS 50 KT.
34 KT...150NE 120SE 75SW 75NW.
FORECAST VALID 02/1200Z 51.7N 43.6W...EXTRATROPICAL
MAX WIND 40 KT...GUSTS 50 KT.
34 KT...240NE 210SE 150SW 150NW.
FORECAST VALID 03/1200Z 56.0N 35.0W...EXTRATROPICAL
MAX WIND 45 KT...GUSTS 55 KT.
34 KT...375NE 325SE 200SW 350NW.
EXTENDED OUTLOOK. NOTE...ERRORS FOR TRACK HAVE AVERAGED NEAR 225 NM
ON DAY 4 AND 300 NM ON DAY 5...AND FOR INTENSITY NEAR 20 KT EACH DAY
OUTLOOK VALID 04/1200Z 57.0N 19.0W...EXTRATROPICAL
MAX WIND 50 KT...GUSTS 60 KT.
OUTLOOK VALID 05/1200Z 58.0N 3.5W...EXTRATROPICAL
MAX WIND 50 KT...GUSTS 60 KT.
REQUEST FOR 3 HOURLY SHIP REPORTS WITHIN 300 MILES OF 41.2N 48.8W
NEXT ADVISORY AT 30/2100Z
$$
FORECASTER BERG/PASCH
197
WTNT42 KNHC 301433
TCDAT2
TROPICAL STORM LAURA DISCUSSION NUMBER 6
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL122008
1100 AM EDT TUE SEP 30 2008
WHILE SOMEWHAT OF A PARADOX...LAURA CAN NOW BE DESIGNATED AS A
TROPICAL CYCLONE DESPITE THE FACT THAT IT CONTINUES TO MOVE
NORTHWARD OVER PROGRESSIVELY COLDER WATERS. THE ONE ASPECT WHICH
WAS HOLDING US BACK FROM DECLARING IT TROPICAL WAS THE UPPER LOW
COLLOCATED WITH THE SYSTEM. WATER VAPOR IMAGERY INDICATES THAT
THIS FEATURE HAS BECOME OFFSET AND STRETCHED TO THE SOUTHWEST OF
LAURA...AND UPPER LEVEL OUTFLOW IS NOW EXPANDING TO THE NORTH OF
THE CYCLONE. IN ADDITION...SCATTEROMETER DATA INDICATE THAT THE
RADIUS OF MAXIMUM WINDS HAS CONTINUED TO CONTRACT TO ABOUT 60 NM.
CLOUD TOP TEMPERATURES ARE NOT ALL THAT COLD...BUT THAT IS QUITE
NORMAL FOR HIGH-LATITUDE TROPICAL CYCLONES DUE TO THE LOWER
TROPOPAUSE. FRANKLY...LAURA NOW LOOKS LIKE A TROPICAL STORM.
THE INITIAL INTENSITY IS HELD AT 50 KT BASED ON AN 0827 UTC QUIKSCAT
PASS ALTHOUGH THE AREA OF STRONGEST WINDS HAS BEEN SHRINKING.
LAURA SHOULD BE ABLE TO HOLD THAT INTENSITY FOR ONLY ANOTHER 12
HOURS OR SO BEFORE MOVING OVER SEA SURFACE TEMPERATURES LESS THAN
18C. GLOBAL MODEL FIELDS INDICATE THAT THERMAL ADVECTION AROUND
THE SYSTEM BECOMES MORE PROMINENT LATER TONIGHT...AND LAURA IS
EXPECTED TO BE EXTRATROPICAL IN 24 HOURS OR SO AS IT MIGRATES INTO
THE COLDER AIR MASS. SOME GRADUAL WEAKENING THROUGH 48 HOURS IS
EXPECTED DUE TO THE COLDER OCEAN WATERS AND MARGINAL BAROCLINIC
FORCING. THEREAFTER...SOME RE-STRENGTHENING AND AN EXPANSION OF
THE WIND FIELD COULD OCCUR AS THE EXTRATROPICAL LOW RACES EAST
WITHIN THE MID-LATITUDE WESTERLIES TOWARDS THE NORTHERN BRITISH
ISLES. EXCEPT FOR A SLIGHT WESTWARD SHIFT IN THE TRACK GUIDANCE AT
36-48 HOURS...THERE HAS BEEN NO SIGNIFICANT CHANGE IN THE GLOBAL
MODELS FOR THIS CYCLE AND THE OFFICIAL FORECAST LIES VERY CLOSE TO
THE MODEL CONSENSUS.
FORECAST POSITIONS AND MAX WINDS
INITIAL 30/1500Z 41.2N 48.8W 50 KT
12HR VT 01/0000Z 42.8N 48.4W 50 KT
24HR VT 01/1200Z 45.5N 47.4W 45 KT...EXTRATROPICAL
36HR VT 02/0000Z 48.7N 45.6W 40 KT...EXTRATROPICAL
48HR VT 02/1200Z 51.7N 43.6W 40 KT...EXTRATROPICAL
72HR VT 03/1200Z 56.0N 35.0W 45 KT...EXTRATROPICAL
96HR VT 04/1200Z 57.0N 19.0W 50 KT...EXTRATROPICAL
120HR VT 05/1200Z 58.0N 3.5W 50 KT...EXTRATROPICAL
$$
FORECASTER BERG/PASCH
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Re: ATL: LAURA - Tropical Storm: Advisories
WTNT42 KNHC 302035
TCDAT2
TROPICAL STORM LAURA DISCUSSION NUMBER 7
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL122008
500 PM EDT TUE SEP 30 2008
A 1653 UTC CIMSS AMSU INTENSITY ESTIMATE CONFIRMS THAT LAURA STILL
HAS MAXIMUM WINDS OF 50 KT. IN ADDITION...THE SATELLITE
PRESENTATION OF THE STORM'S CENTRAL FEATURES HAS NOT CHANGED
APPRECIABLY SINCE THIS MORNING SO THERE IS LITTLE REASON TO CHANGE
THE INITIAL INTENSITY. ALTHOUGH LAURA IS CURRENTLY A TROPICAL
CYCLONE...VISIBLE IMAGERY SUGGESTS THAT SOME THERMAL ADVECTION IS
BEGINNING TO OCCUR AS COLD AIR STRATUS CLOUDS WRAP AROUND THE WEST
SIDE OF THE CIRCULATION. GLOBAL MODEL FIELDS INDICATE THAT THE
EXTRATROPICAL TRANSITION PROCESS WILL CONTINUE THROUGH TONIGHT...
AND LAURA COULD BE FULLY NON-TROPICAL IN 18-24 HOURS. THE SYSTEM IS
NOW OVER SEA SURFACE TEMPERATURES NEAR 21C AND IS QUICKLY LOSING
ITS TROPICAL ENERGY SOURCE...SO SOME WEAKENING IS SHOWN IN THE
OFFICIAL FORECAST OVER THE NEXT 36 HOURS. THEREAFTER...BAROCLINIC
FORCING WILL BECOME MORE PROMINENT AS THE EXTRATROPICAL LOW BECOMES
EMBEDDED IN THE WESTERLIES...AND SOME RE-STRENGTHENING COULD OCCUR.
LAURA IS NOW MOVING JUST EAST OF DUE NORTH AT 010/12. MOST OF THE
TRACK GUIDANCE IS TIGHTLY CLUSTERED THROUGH 5 DAYS AND THE OFFICIAL
FORECAST REMAINS VERY CLOSE TO THE MODEL CONSENSUS. THE NHC
FORECAST TRACK SHOWS A SLIGHT WESTWARD BEND AT 36-48 HOURS DUE TO
THE INFLUENCE OF A SHORTWAVE TROUGH OVER THE CANADIAN
MARITIMES...BUT AFTER THAT LAURA IS ACCELERATED EASTWARD ACROSS THE
NORTH ATLANTIC. A 120-HOUR POSITION IS NOT GIVEN IN THIS FORECAST
SINCE IT WOULD BE LOCATED EAST OF THE PRIME MERIDIAN OVER THE NORTH
SEA...AND THE LOW COULD BE ABSORBED BY A FRONTAL BOUNDARY BY THEN
ANYWAY.
FORECAST POSITIONS AND MAX WINDS
INITIAL 30/2100Z 42.3N 48.6W 50 KT
12HR VT 01/0600Z 44.0N 48.0W 45 KT...BECOMING EXTRATROPICAL
24HR VT 01/1800Z 46.8N 46.8W 40 KT...EXTRATROPICAL
36HR VT 02/0600Z 50.0N 45.1W 40 KT...EXTRATROPICAL
48HR VT 02/1800Z 53.1N 42.4W 45 KT...EXTRATROPICAL
72HR VT 03/1800Z 56.5N 31.5W 45 KT...EXTRATROPICAL
96HR VT 04/1800Z 57.0N 17.0W 45 KT...EXTRATROPICAL
120HR VT 05/1800Z...ABSORBED
$$
FORECASTER BERG/PASCH
TCDAT2
TROPICAL STORM LAURA DISCUSSION NUMBER 7
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL122008
500 PM EDT TUE SEP 30 2008
A 1653 UTC CIMSS AMSU INTENSITY ESTIMATE CONFIRMS THAT LAURA STILL
HAS MAXIMUM WINDS OF 50 KT. IN ADDITION...THE SATELLITE
PRESENTATION OF THE STORM'S CENTRAL FEATURES HAS NOT CHANGED
APPRECIABLY SINCE THIS MORNING SO THERE IS LITTLE REASON TO CHANGE
THE INITIAL INTENSITY. ALTHOUGH LAURA IS CURRENTLY A TROPICAL
CYCLONE...VISIBLE IMAGERY SUGGESTS THAT SOME THERMAL ADVECTION IS
BEGINNING TO OCCUR AS COLD AIR STRATUS CLOUDS WRAP AROUND THE WEST
SIDE OF THE CIRCULATION. GLOBAL MODEL FIELDS INDICATE THAT THE
EXTRATROPICAL TRANSITION PROCESS WILL CONTINUE THROUGH TONIGHT...
AND LAURA COULD BE FULLY NON-TROPICAL IN 18-24 HOURS. THE SYSTEM IS
NOW OVER SEA SURFACE TEMPERATURES NEAR 21C AND IS QUICKLY LOSING
ITS TROPICAL ENERGY SOURCE...SO SOME WEAKENING IS SHOWN IN THE
OFFICIAL FORECAST OVER THE NEXT 36 HOURS. THEREAFTER...BAROCLINIC
FORCING WILL BECOME MORE PROMINENT AS THE EXTRATROPICAL LOW BECOMES
EMBEDDED IN THE WESTERLIES...AND SOME RE-STRENGTHENING COULD OCCUR.
LAURA IS NOW MOVING JUST EAST OF DUE NORTH AT 010/12. MOST OF THE
TRACK GUIDANCE IS TIGHTLY CLUSTERED THROUGH 5 DAYS AND THE OFFICIAL
FORECAST REMAINS VERY CLOSE TO THE MODEL CONSENSUS. THE NHC
FORECAST TRACK SHOWS A SLIGHT WESTWARD BEND AT 36-48 HOURS DUE TO
THE INFLUENCE OF A SHORTWAVE TROUGH OVER THE CANADIAN
MARITIMES...BUT AFTER THAT LAURA IS ACCELERATED EASTWARD ACROSS THE
NORTH ATLANTIC. A 120-HOUR POSITION IS NOT GIVEN IN THIS FORECAST
SINCE IT WOULD BE LOCATED EAST OF THE PRIME MERIDIAN OVER THE NORTH
SEA...AND THE LOW COULD BE ABSORBED BY A FRONTAL BOUNDARY BY THEN
ANYWAY.
FORECAST POSITIONS AND MAX WINDS
INITIAL 30/2100Z 42.3N 48.6W 50 KT
12HR VT 01/0600Z 44.0N 48.0W 45 KT...BECOMING EXTRATROPICAL
24HR VT 01/1800Z 46.8N 46.8W 40 KT...EXTRATROPICAL
36HR VT 02/0600Z 50.0N 45.1W 40 KT...EXTRATROPICAL
48HR VT 02/1800Z 53.1N 42.4W 45 KT...EXTRATROPICAL
72HR VT 03/1800Z 56.5N 31.5W 45 KT...EXTRATROPICAL
96HR VT 04/1800Z 57.0N 17.0W 45 KT...EXTRATROPICAL
120HR VT 05/1800Z...ABSORBED
$$
FORECASTER BERG/PASCH
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cycloneye
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Re: ATL: LAURA - Tropical Storm: Advisories
WTNT42 KNHC 010233
TCDAT2
TROPICAL STORM LAURA DISCUSSION NUMBER 8
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL122008
1100 PM EDT TUE SEP 30 2008
I WAS TEMPTED TO TERMINATE ADVISORIES ON LAURA TONIGHT SINCE
CONVECTION HAS BEEN GRADUALLY DIMINISHING AND THE CLOUD PATTERN HAS
BECOME MUCH LESS DISTINCT. HOWEVER...LAURA CANNOT BE CALLED A
REMNANT LOW YET AND IT IS NOT EXTRATROPICAL ENOUGH TO BE CALLED
ONE. BASED ON SATELLITE ESTIMATES FROM TAFB AND SAB AND
CONTINUITY...THE INITIAL INTENSITY HAS BEEN ADJUSTED DOWN TO 45
KNOTS. LAURA IS MOVING OVER COLD WATERS AND IS BECOMING INVOLVED
WITH COLD AIR. THIS SUGGESTS THAT LAURA SHOULD BE EXTRATROPICAL
IN 12 HOUR OR LESS. ONCE EXTRATROPICAL...NO SIGNIFICANT CHANGES IN
INTENSITY ARE ANTICIPATED.
THE BEST ESTIMATE OF THE MOTION OF THE LARGE HOLE ASSOCIATED WITH
THE CENTER IS 015 AT 14 KNOTS. LAURA SHOULD TURN MORE TO THE
NORTH-NORTHEAST AND NORTHEAST WITH AN INCREASE IN FORWARD SPEED
AHEAD OF A VERY DEEP TROUGH OVER THE EASTERN UNITED STATES. IT
SHOULD THEN TURN EASTWARD ADVECTED BY THE WESTERLIES. THIS IS THE
SOLUTION PROVIDED BY MOST OF THE RELIABLE GUIDANCE.
FORECAST POSITIONS AND MAX WINDS
INITIAL 01/0300Z 43.6N 48.0W 45 KT
12HR VT 01/1200Z 45.5N 47.0W 40 KT...EXTRATROPICAL
24HR VT 02/0000Z 48.5N 45.5W 40 KT...EXTRATROPICAL
36HR VT 02/1200Z 52.5N 43.5W 40 KT...EXTRATROPICAL
48HR VT 03/0000Z 55.0N 40.0W 45 KT...EXTRATROPICAL
72HR VT 04/0000Z 56.5N 27.0W 45 KT...EXTRATROPICAL
96HR VT 05/0000Z 56.5N 13.0W 45 KT...EXTRATROPICAL
120HR VT 06/0000Z...ABSORBED BY FRONTAL SYSTEM
$$
FORECASTER AVILA
TCDAT2
TROPICAL STORM LAURA DISCUSSION NUMBER 8
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL122008
1100 PM EDT TUE SEP 30 2008
I WAS TEMPTED TO TERMINATE ADVISORIES ON LAURA TONIGHT SINCE
CONVECTION HAS BEEN GRADUALLY DIMINISHING AND THE CLOUD PATTERN HAS
BECOME MUCH LESS DISTINCT. HOWEVER...LAURA CANNOT BE CALLED A
REMNANT LOW YET AND IT IS NOT EXTRATROPICAL ENOUGH TO BE CALLED
ONE. BASED ON SATELLITE ESTIMATES FROM TAFB AND SAB AND
CONTINUITY...THE INITIAL INTENSITY HAS BEEN ADJUSTED DOWN TO 45
KNOTS. LAURA IS MOVING OVER COLD WATERS AND IS BECOMING INVOLVED
WITH COLD AIR. THIS SUGGESTS THAT LAURA SHOULD BE EXTRATROPICAL
IN 12 HOUR OR LESS. ONCE EXTRATROPICAL...NO SIGNIFICANT CHANGES IN
INTENSITY ARE ANTICIPATED.
THE BEST ESTIMATE OF THE MOTION OF THE LARGE HOLE ASSOCIATED WITH
THE CENTER IS 015 AT 14 KNOTS. LAURA SHOULD TURN MORE TO THE
NORTH-NORTHEAST AND NORTHEAST WITH AN INCREASE IN FORWARD SPEED
AHEAD OF A VERY DEEP TROUGH OVER THE EASTERN UNITED STATES. IT
SHOULD THEN TURN EASTWARD ADVECTED BY THE WESTERLIES. THIS IS THE
SOLUTION PROVIDED BY MOST OF THE RELIABLE GUIDANCE.
FORECAST POSITIONS AND MAX WINDS
INITIAL 01/0300Z 43.6N 48.0W 45 KT
12HR VT 01/1200Z 45.5N 47.0W 40 KT...EXTRATROPICAL
24HR VT 02/0000Z 48.5N 45.5W 40 KT...EXTRATROPICAL
36HR VT 02/1200Z 52.5N 43.5W 40 KT...EXTRATROPICAL
48HR VT 03/0000Z 55.0N 40.0W 45 KT...EXTRATROPICAL
72HR VT 04/0000Z 56.5N 27.0W 45 KT...EXTRATROPICAL
96HR VT 05/0000Z 56.5N 13.0W 45 KT...EXTRATROPICAL
120HR VT 06/0000Z...ABSORBED BY FRONTAL SYSTEM
$$
FORECASTER AVILA
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206
WTNT42 KNHC 011438
TCDAT2
TROPICAL STORM LAURA DISCUSSION NUMBER 10
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL122008
1100 AM EDT WED OCT 01 2008
ALTHOUGH A SMALL PATCH OF CONVECTION REMAINS...THERE IS NOT ENOUGH
DEEP CONVECTION FOR LAURA TO BE CONSIDERED A TROPICAL CYCLONE...AND
THIS WILL BE THE LAST ADVISORY. I RATHER LIKE THE CANADIAN
HURRICANE CENTER'S TERM POST-TROPICAL...WHICH SIMPLY MEANS NO
LONGER TROPICAL...TO DESCRIBE WHAT LAURA HAS BECOME. THERE IS NOT
REALLY ENOUGH EVIDENCE OF FRONTAL STRUCTURE YET TO CONSIDER LAURA
EXTRATROPICAL IN THE TRADITIONAL SENSE...AND SOME USERS MIGHT INFER
A WEAK SYSTEM IF WE USED THE TERM REMNANT LOW...WHICH IS
MOST-COMMONLY APPLIED TO DECAYING SYSTEMS IN THE EASTERN PACIFIC
BASIN.
A QUIKSCAT PASS THIS MORNING SHOWS THAT THE MAXIMUM WINDS REMAIN
NEAR 40 KT...PERHAPS EVEN A BIT HIGHER. A TRANSITION TO A FULLY
EXTRATROPICAL STRUCTURE IS EXPECTED OVER THE NEXT DAY OR SO...AND
THE GFS SUGGESTS SOME REINVIGORATION OF THE EXTRATROPICAL REMNANT
OF LAURA IN THREE OR FOUR DAYS. OTHER GLOBAL GUIDANCE...HOWEVER...
SHOWS THE CIRCULATION BECOMING ELONGATED AND DISSIPATING WITHIN A
FRONTAL ZONE. THE OFFICIAL FORECAST WILL CALL FOR AN EXPANSION OF
THE WIND RADII IN GENERAL AGREEMENT WITH THE GFS...BUT FOLLOWS A
CONSENSUS OF THE GLOBAL GUIDANCE IN CARRYING A TRACK ONLY OUT TO 72
HOURS.
FUTURE INFORMATION ON THIS SYSTEM CAN BE FOUND IN HIGH SEAS
FORECASTS ISSUED BY THE NATIONAL WEATHER SERVICE...UNDER AWIPS
HEADER NFDHSFAT1 AND WMO HEADER FZNT01 KWBC.
FORECAST POSITIONS AND MAX WINDS
INITIAL 01/1500Z 46.5N 46.5W 40 KT...POST-TROPICAL
12HR VT 02/0000Z 48.9N 45.6W 40 KT...EXTRATROPICAL
24HR VT 02/1200Z 52.2N 43.5W 40 KT...EXTRATROPICAL
36HR VT 03/0000Z 55.0N 39.8W 40 KT...EXTRATROPICAL
48HR VT 03/1200Z 56.0N 33.0W 40 KT...EXTRATROPICAL
72HR VT 04/1200Z 56.5N 20.0W 40 KT...EXTRATROPICAL
96HR VT 05/1200Z...ABSORBED
$$
FORECASTER FRANKLIN
WTNT42 KNHC 011438
TCDAT2
TROPICAL STORM LAURA DISCUSSION NUMBER 10
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL122008
1100 AM EDT WED OCT 01 2008
ALTHOUGH A SMALL PATCH OF CONVECTION REMAINS...THERE IS NOT ENOUGH
DEEP CONVECTION FOR LAURA TO BE CONSIDERED A TROPICAL CYCLONE...AND
THIS WILL BE THE LAST ADVISORY. I RATHER LIKE THE CANADIAN
HURRICANE CENTER'S TERM POST-TROPICAL...WHICH SIMPLY MEANS NO
LONGER TROPICAL...TO DESCRIBE WHAT LAURA HAS BECOME. THERE IS NOT
REALLY ENOUGH EVIDENCE OF FRONTAL STRUCTURE YET TO CONSIDER LAURA
EXTRATROPICAL IN THE TRADITIONAL SENSE...AND SOME USERS MIGHT INFER
A WEAK SYSTEM IF WE USED THE TERM REMNANT LOW...WHICH IS
MOST-COMMONLY APPLIED TO DECAYING SYSTEMS IN THE EASTERN PACIFIC
BASIN.
A QUIKSCAT PASS THIS MORNING SHOWS THAT THE MAXIMUM WINDS REMAIN
NEAR 40 KT...PERHAPS EVEN A BIT HIGHER. A TRANSITION TO A FULLY
EXTRATROPICAL STRUCTURE IS EXPECTED OVER THE NEXT DAY OR SO...AND
THE GFS SUGGESTS SOME REINVIGORATION OF THE EXTRATROPICAL REMNANT
OF LAURA IN THREE OR FOUR DAYS. OTHER GLOBAL GUIDANCE...HOWEVER...
SHOWS THE CIRCULATION BECOMING ELONGATED AND DISSIPATING WITHIN A
FRONTAL ZONE. THE OFFICIAL FORECAST WILL CALL FOR AN EXPANSION OF
THE WIND RADII IN GENERAL AGREEMENT WITH THE GFS...BUT FOLLOWS A
CONSENSUS OF THE GLOBAL GUIDANCE IN CARRYING A TRACK ONLY OUT TO 72
HOURS.
FUTURE INFORMATION ON THIS SYSTEM CAN BE FOUND IN HIGH SEAS
FORECASTS ISSUED BY THE NATIONAL WEATHER SERVICE...UNDER AWIPS
HEADER NFDHSFAT1 AND WMO HEADER FZNT01 KWBC.
FORECAST POSITIONS AND MAX WINDS
INITIAL 01/1500Z 46.5N 46.5W 40 KT...POST-TROPICAL
12HR VT 02/0000Z 48.9N 45.6W 40 KT...EXTRATROPICAL
24HR VT 02/1200Z 52.2N 43.5W 40 KT...EXTRATROPICAL
36HR VT 03/0000Z 55.0N 39.8W 40 KT...EXTRATROPICAL
48HR VT 03/1200Z 56.0N 33.0W 40 KT...EXTRATROPICAL
72HR VT 04/1200Z 56.5N 20.0W 40 KT...EXTRATROPICAL
96HR VT 05/1200Z...ABSORBED
$$
FORECASTER FRANKLIN
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