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Tropical Storm MARIA


ZCZC MIATCDAT4 ALL
TTAA00 KNHC DDHHMM
 
TROPICAL STORM MARIA DISCUSSION NUMBER  18
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL142011
1100 PM AST SAT SEP 10 2011
 
REPORTS FROM AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT AND
SURFACE OBSERVATIONS FROM THE LEEWARD ISLANDS SHOW THAT THE WIND
CIRCULATION OF MARIA HAS BECOME BETTER DEFINED DURING THE PAST
SEVERAL HOURS...ALTHOUGH THE SOUTHWEST SIDE REMAINS WEAK.  THE
AIRCRAFT REPORTED MAXIMUM 850 MB FLIGHT-LEVEL WINDS OF 59 KT AND
ESTIMATED THE CENTRAL PRESSURE NEAR 1005 MB.  THERE WERE NUMEROUS
40-45 KT WIND ESTIMATES FROM THE SFMR THAT LOOKED RELIABLE...SO THE
INITIAL INTENSITY IS INCREASED TO 45 KT.  OVERALL...THE SYSTEM NOW
HAS THE APPEARANCE OF A SHEARED TROPICAL CYCLONE WITH STRONG
CONVECTION NEAR AND TO THE NORTHEAST OF THE LOW-LEVEL CENTER.
 
THE INITIAL MOTION IS 315/9...A LITTLE SLOWER THAN EARLIER.  OTHER
THAN THAT...THE TRACK FORECAST REASONING HAS CHANGED LITTLE SINCE
THE LAST ADVISORY.  FOR THE NEXT COUPLE OF DAYS...A COMBINATION OF
THE SUBTROPICAL RIDGE TO THE NORTH AND AN UPPER-LEVEL LOW NEAR
25N64W SHOULD STEER MARIA GENERALLY NORTHWESTWARD.  AFTER THAT...A
DEEP-LAYER WESTERLY TROUGH ADVANCING THROUGH THE EASTERN UNITED
STATES SHOULD WEAKEN THE RIDGE AND ALLOW MARIA TO RECURVE INTO THE
WESTERLIES.  THERE IS SOME SPREAD IN THE TRACK GUIDANCE.  THE UKMET
AND ECMWF SHOW A MORE WESTERLY MOTION DURING THE FIRST 72 HOURS AND
ARE SLOWER TO RECURVE.  THE GFS SHOWS A MORE NORTHWARD MOTION AND
IS THE FASTEST TO MOVE THE CYCLONE INTO THE WESTERLIES.  THE NEW
TRACK FORECAST IS SHIFTED A LITTLE TO THE EAST OF THE PREVIOUS
FORECAST...BUT LIES A LITTLE TO THE LEFT OF THE CENTER OF THE
GUIDANCE ENVELOPE THROUGH 72 HOURS.  THE 96 AND 120 HOUR POINTS
COMPROMISE IN SPEED BETWEEN THE FASTER GFS AND THE SLOWER
ECMWF/UKMET.
 
MARIA IS CURRENTLY EXPERIENCING 15-20 KT OF SOUTHWESTERLY VERTICAL
WIND SHEAR DUE TO THE INTERACTION WITH THE UPPER-LEVEL LOW.  THE
DYNAMICAL MODELS ARE IN POOR AGREEMENT ON HOW MUCH SHEAR THE STORM
SHOULD CONTINUE TO EXPERIENCE DURING THE FORECAST PERIOD.  THE
GFS...NOGAPS...AND CANADIAN MODELS FORECAST THE SHEAR TO DECREASE
SIGNIFICANTLY BY 72 HOURS...WHILE THE UKMET AND ECMWF FORECAST A
MORE HOSTILE ENVIRONMENT AND A WEAKER MARIA.  THE MAJORITY OF THE
INTENSITY FORECAST GUIDANCE CALLS FOR MARIA TO BE A HURRICANE BY 72
HOURS.  DUE TO THE UNCERTAINTIES IN HOW MARIA WILL INTERACT WITH
THE UPPER-LEVEL LOW...THE NEW INTENSITY FORECAST WILL NOT CALL FOR
MARIA TO BECOME A HURRICANE AT THIS TIME.  INSTEAD...THE INTENSITY
FORECAST IS SIMILAR TO THE PREVIOUS FORECAST WITH SLOW
INTENSIFICATION DURING THE 24-96 HOUR PERIOD.  THIS FORECAST IS AT
THE LOWER EDGE OF THE INTENSITY GUIDANCE.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  11/0300Z 18.5N  62.9W   45 KT  50 MPH
 12H  11/1200Z 19.6N  64.0W   45 KT  50 MPH
 24H  12/0000Z 21.0N  65.4W   45 KT  50 MPH
 36H  12/1200Z 22.3N  66.8W   50 KT  60 MPH
 48H  13/0000Z 23.3N  68.1W   50 KT  60 MPH
 72H  14/0000Z 26.0N  69.5W   55 KT  65 MPH
 96H  15/0000Z 32.0N  69.0W   60 KT  70 MPH
120H  16/0000Z 39.0N  63.5W   60 KT  70 MPH
 
$$
FORECASTER BEVEN
 
NNNN


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Page last modified: Tuesday, 17-Jul-2012 13:44:00 UTC