October 2010 | Main | May 2011
November 5, 2010
HURRICANE TOMAS DISCUSSION NUMBER 29
Tomas is a hurricane again and preparing to shoot straight through the Windward Passage between Haiti and Cuba, before heading to the Turks & Caicos and southern Bahamas:
HURRICANE TOMAS DISCUSSION NUMBER 29
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL212010
500 AM EDT FRI NOV 05 2010
TOMAS HAS REGAINED HURRICANE STRENGTH. THE AIR FORCE HURRICANE
HUNTERS FOUND A PEAK 850 MB FLIGHT-LEVEL WIND OF 88 KT AND MAXIMUM
SFMR-OBSERVED SURFACE WINDS OF 75 KT. THE LATTER OBSERVATION
APPEARED TO BE SOMEWHAT OF A SPIKE IN THE RECORD...AND USING A
BLEND OF THE SURFACE AND FLIGHT-LEVEL DATA GIVES 70 KT FOR THE
CURRENT INTENSITY ESTIMATE. OBSERVATIONS FROM THE AIRCRAFT AND A
TRMM MICROWAVE OVERPASS SUGGEST THAT THE CYCLONE IS TILTED
NORTHWARD AS A RESULT OF SOUTHERLY OR SOUTH-SOUTHWESTERLY VERTICAL
WIND SHEAR. SATELLITE IMAGERY SHOWS A WELL-DEFINED CENTRAL DENSE
OVERCAST...WITH CLOUD TOP TEMPS APPROACHING -90C.
THE INITIAL MOTION ESTIMATE IS 035/08. TOMAS IS LOCATED ON THE EAST
SIDE OF AN UNUSUALLY DEEP MID- TO UPPER-LEVEL TROUGH CURRENTLY
AMPLIFYING OVER THE EASTERN UNITED STATES. THE CYCLONE SHOULD
GRADUALLY BECOME EMBEDDED IN AN INCREASING SOUTHWESTERLY WIND FLOW
AHEAD OF THIS SYSTEM DURING THE NEXT COUPLE OF DAYS AND MOVE ON A
GENERAL NORTHEASTWARD COURSE WITH SOME INCREASE IN FORWARD
SPEED. AFTER 48 HOURS...TOMAS SHOULD GRADUALLY SLOW DOWN AND TURN
EAST-NORTHEASTWARD AND THEN EASTWARD IN A WEAKER LOW-LEVEL
WESTERLY STEERING FLOW AS THE INCREASING SHEAR REDUCES TOMAS TO A
SHALLOWER FEATURE. THIS IS THE GENERAL SCENARIO DEPICTED BY THE
GFS AND U.K. MET. OFFICE GLOBAL MODELS. AN ALTERNATIVE EVOLUTION
IS SUGGESTED BY SOME OF THE OTHER GUIDANCE SUCH AS THE ECMWF. THE
LATTER MODEL SHOWS A STRONGER CYCLONE NEAR THE END OF THE FORECAST
PERIOD...PRESUMABLY DUE TO BAROCLINIC FORCING...THAT MOVES MORE
QUICKLY TOWARDS THE NORTHEAST. THE OFFICIAL NHC TRACK FORECAST IS
VIRTUALLY UNCHANGED FROM THE PREVIOUS ONE AND IS ON THE EASTERN
SIDE OF THE GUIDANCE ENVELOPE.
TOMAS STILL HAS ABOUT 24 HOURS OR SO TO STRENGTHEN IN AN ENVIRONMENT
OF RELATIVELY LOW SHEAR...HIGH MOISTURE...AND OVER WARM WATERS.
AFTER THAT...A RAPID INCREASE IN SOUTHWESTERLY SHEAR ASSOCIATED
WITH THE EASTERN U.S. TROUGH...NOT TO MENTION DRIER AND COOLER
ASSOCIATED WITH THE SAME FEATURE IMPINGING ON THE CIRCULATION...
SHOULD BRING ABOUT A PRONOUNCED WEAKENING PHASE. THE NEW NHC
FORECAST IS LOWER THAN THE SHIPS/LGEM INTENSITY GUIDANCE BUT ABOUT
THE SAME AS THE PREVIOUS OFFICIAL FORECAST...INDICATING
INTENSIFICATION TO HURRICANE STRENGTH WITHIN 24 HOURS AND WEAKENING
TO A REMNANT LOW IN 96 HOURS. WEAKENING AFTER 48 HOURS COULD BE
MORE RAPID THAN INDICATED...CONSIDERING THAT THE SHEAR COULD BE
HIGHER THAN 60 KT AFTER 60 HOURS.
REGARDLESS OF THE EXACT TRACK AND INTENSITY OF TOMAS...THE MOST
SIGNIFICANT THREAT FROM THIS TROPICAL CYCLONE SHOULD CONTINUE TO BE
HEAVY RAINFALL...WHICH COULD PRODUCE FLASH FLOODING AND LIFE-
THREATENING MUD SLIDES OVER PORTIONS OF HAITI AND THE DOMINICAN
REPUBLIC DURING THE NEXT COUPLE OF DAYS.
Hurricane Tomas Heads for Haiti, Cuba
November 4, 2010
Tomas Update, Thursday morning
This storm is proving difficult to forecast and the intensity models are are changing all the time - see this key passage from the NHC 5 AM report:
"REGARDLESS OF THE EXACT TRACK AND INTENSITY OF TOMAS...THE MOST
SIGNIFICANT THREAT FROM THIS TROPICAL CYCLONE IS HEAVY RAINFALL...
WHICH COULD PRODUCE FLASH FLOODING AND LIFE-THREATENING MUD SLIDES
OVER HAITI AND THE DOMINICAN REPUBLIC DURING THE NEXT COUPLE OF
DAYS."
The one thing for sure is whether it is a tropical storm or hurricane is that there will be lots of rain and that may be more dangerous than the wind. It is still tracking between Haiti and Cuba through the Windward Passage, with Jamaica to the left, and the Turks & Caicos also in line at the moment. Tracking map here.
The full discussion:
TROPICAL STORM TOMAS DISCUSSION NUMBER 25
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL212010
500 AM EDT THU NOV 04 2010
SATELLITE PICTURES SUGGEST THAT THE CLOUD PATTERN OF TOMAS HAS NOT
CHANGED SIGNIFICANTLY DURING THE LAST SEVERAL HOURS. HOWEVER...
DATA FROM AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT INDICATE
THAT THE PRESSURE HAS FALLEN TO 997 MB WITH MAXIMUM SURFACE WINDS
OF 41 KT. DESPITE THE AIRCRAFT DATA WHICH ARE INDICATIVE OF SLIGHT
STRENGTHENING...THE VORTEX HAS BEEN TILTED IN THE VERTICAL BASED
UPON COMPARISON OF EARLIER NOAA AND AIR FORCE AIRCRAFT DATA.
GIVEN THE SIGNIFICANTLY LOWER CENTRAL PRESSURE FROM THE AIRCRAFT...
THE INITIAL INTENSITY IS INCREASED TO 45 KT FOR THIS ADVISORY.
THE CURRENT MOTION ESTIMATE REMAINS 330/06. THE FORECAST PHILOSOPHY
REGARDING THE TRACK OF TOMAS IS UNCHANGED. TOMAS SHOULD BE STEERED
NORTH-NORTHWESTWARD TO NORTHWARD AROUND A LOW- TO MID-LEVEL RIDGE
LOCATED OVER THE WEST CENTRAL ATLANTIC TODAY. AFTER THAT...TOMAS
SHOULD BEGIN TO ENCOUNTER AN INCREASING SOUTHWESTERLY FLOW
ASSOCIATED WITH AN ANOMALOUSLY DEEP MID- TO UPPER-LEVEL TROUGH
MOVING ACROSS EASTERN NORTH AMERICA AND TURN NORTHEASTWARD WHILE
ACCELERATING. EVEN THOUGH THE SYNOPTIC REASONING HAS NOT CHANGED
FROM THE PREVIOUS PACKAGE...THE OFFICIAL FORECAST TRACK IS SHIFTED
TO THE LEFT ON ACCOUNT OF THE MOST RECENT AIRCRAFT CENTER FIXES.
ALTHOUGH LARGE-SCALE FACTORS OF MODERATELY LOW SHEAR AND WARM WATERS
ARE FAVORABLE FOR FURTHER INTENSIFICATION OF TOMAS...THE VERTICAL
TILT OF THE VORTEX AND THE BROAD NATURE OF THE CIRCULATION MAY
ARGUE AGAINST A RAPID INCREASE IN STRENGTH. INTERESTINGLY...THE
SHIPS RAPID INTENSIFICATION INDEX THAT HAD BEEN SHOWING THE
POTENTIAL FOR A 30-KT INCREASE WITHIN THE NEXT 24 HOURS IS NOT AS
HIGH AS IT WAS BEFORE. THE NEW NHC FORECAST IS SIMILAR TO THE
PREVIOUS ONE AND ASSUMES THAT THE LARGE-SCALE ENVIRONMENT SHOULD BE
CONDUCIVE ENOUGH TO ALLOW FOR STENGTHENING DURING THE NEXT 24-36
HOURS. BEYOND 36 HOURS...STRONG AND INCREASING SOUTHWESTERLY SHEAR
OVER THE WESTERN ATLANTIC IS FORECAST TO CAUSE WEAKENING...PERHAPS
AT A MORE RAPID PACE THAN INDICATED IN THE CURRENT FORECAST. THE
NEW NHC FORECAST IS REDUCED FROM THE PREVIOUS ONE AT LATER FORECAST
TIMES GIVEN THE STRONG FORECAST SHEAR.
REGARDLESS OF THE EXACT TRACK AND INTENSITY OF TOMAS...THE MOST
SIGNIFICANT THREAT FROM THIS TROPICAL CYCLONE IS HEAVY RAINFALL...
WHICH COULD PRODUCE FLASH FLOODING AND LIFE-THREATENING MUD SLIDES
OVER HAITI AND THE DOMINICAN REPUBLIC DURING THE NEXT COUPLE OF
DAYS.
November 2, 2010
Tropical Storm Tomas Damage
Tomas already is a deadly storm, responsible for many deaths on St. Lucia and property damage there and elsewhere. Here is some tragic video from St. Lucia:
Tropical Storm Tomas Update
Tomas, downgraded now to a tropical storm, is taking its time, meandering in the Caribbean Sea, and starting to strengthen again. This storm has the models a bit confused, and it could take a variety of tracks, but the NHC does seem to think it will regain hurricane force again before it dies out.
TROPICAL STORM TOMAS DISCUSSION NUMBER 17
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL212010
500 AM EDT TUE NOV 02 2010
TOMAS HAS THE APPEARANCE OF A GRADUALLY STRENGTHENING TROPICAL
STORM. OVERNIGHT...THERE HAS BEEN A SUBSTANTIAL INCREASE IN THE
ASSOCIATED DEEP CONVECTION. ALTHOUGH MOST OF THE THUNDERSTORM
ACTIVITY IS OCCURRING OVER THE EASTERN AND NORTHEASTERN PORTIONS OF
THE CIRCULATION...DEEP CONVECTION HAS RECENTLY BEEN INCREASING NEAR
THE CENTER. ENHANCED IR IMAGERY ALSO SUGGESTS SOME BANDING
FEATURES DEVELOPING OVER THE NORTHEAST QUADRANT. ON THE FINAL PASS
OF AN AIR FORCE HURRICANE HUNTER PLANE OUTBOUND FROM THE CENTER
OVER THE NORTHEAST QUADRANT...THE MAXIMUM UNFLAGGED SFMR-MEASURED
SURFACE WIND SPEED WAS 44 KT. THE INTENSITY IS ADJUSTED SLIGHTLY
UPWARD...TO 45 KT...ON THIS ADVISORY. TOMAS IS FORECAST TO MOVE
OVER WATERS OF INCREASINGLY HIGH OCEANIC HEAT CONTENT AND ALTHOUGH
SOME SOUTHWESTERLY SHEAR WILL PROBABLY IMPACT THE SYSTEM...THE
SHEAR IS NOT LIKELY TO BECOME VERY STRONG FOR THE NEXT FEW DAYS.
THE OFFICIAL INTENSITY FORECAST IS SIMILAR TO THE PREVIOUS ONE AND
BRINGS TOMAS TO HURRICANE INTENSITY IN A COUPLE OF DAYS. THIS IS
SIMILAR TO THE RELIABLE LGEM GUIDANCE BUT BELOW THE GFDL FORECAST
INTENSITY PREDICTION.
BASED ON THE HURRICANE HUNTER FIXES...THE STORM CONTINUES MOVING
WESTWARD...OR ABOUT 270/10. THE TRACK FORECAST REASONING FOR THE
NEXT 3 TO 4 DAYS REMAINS THE SAME AS BEFORE. TOMAS SHOULD BE
STEERED ALONG THE SOUTHERN AND SOUTHWESTERN PERIPHERY OF A LOW- TO
MID-LEVEL RIDGE FOR THE NEXT COUPLE OF DAYS. BY 72-96 HOURS...THE
FLOW AHEAD OF A LARGE MID-TROPOSPHERIC TROUGH SHOULD TURN THE
DEEPENING CYCLONE SHARPLY NORTHWARD AND NORTH-NORTHEASTWARD. BY
THE END OF THE FORECAST PERIOD...THE GLOBAL MODELS SUGGEST THAT THE
TROUGH COULD SWING NORTHEASTWARD AND NOT COMPLETELY PICK UP TOMAS.
THEREFORE THERE IS A POSSIBILITY THAT THE TROPICAL CYCLONE COULD
LINGER NEAR NORTHERN HISPANIOLA FOR A DAY OR TWO...BEFORE THE
WESTERLIES EVENTUALLY CARRY IT FARTHER OUT INTO THE ATLANTIC. THAT
POSSIBILITY...HOWEVER...IS NOT EXPLICITLY SHOWN IN THE OFFICIAL
TRACK FORECAST AT THIS TIME.
