000
WTNT44 KNHC 090851
TCDAT4
 
TROPICAL STORM HUMBERTO DISCUSSION NUMBER   3
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092013
500 AM AST MON SEP 09 2013
 
SINCE THE PREVIOUS ADVISORY...DEEP CONVECTION WITH A LARGE AREA OF
CLOUD TOPS COLDER THAN -80C HAS DEVELOPED MAINLY WEST THROUGH NORTH
OF THE LOW-LEVEL CENTER...WITH A FEW STRONG CELLS HAVING RECENTLY
FORMED VERY NEAR THE CENTER. THE INITIAL INTENSITY HAS BEEN
INCREASED TO 35 KT BASED ON CONSENSUS T2.5/35 KT INTENSITY
ESTIMATES FROM BOTH TAFB AND SAB...AND A 34-KT ADT ESTIMATE. AS A
RESULT...THE SYSTEM HAS BEEN NAMED HUMBERTO. UPPER-LEVEL OUTFLOW IS
GOOD IN ALL QUADRANTS EXCEPT TO THE NORTHEAST WHERE SOME MODEST
NORTHEASTERLY SHEAR IS RESTRICTING THE OUTFLOW.
 
HUMBERTO IS MOVING AT 280/10 KT...AND THE CYCLONE SHOULD CONTINUE
THIS GENERAL MOTION FOR THE NEXT DAY OR SO. AFTERWARDS...THE GLOBAL
AND REGIONAL MODELS ARE IN GOOD AGREEMENT ON AN UPPER-LEVEL LOW
OVER THE IBERIAN PENINSULA DIGGING SOUTHWESTWARD ACROSS THE CANARY
ISLANDS DURING THE NEXT FEW DAYS AND ERODING THE STRONG SUBTROPICAL
RIDGE THAT CURRENTLY EXTENDS FROM THE AZORES SOUTHEASTWARD TO
WESTERN AFRICA. THIS RADICAL CHANGE IN THE STEERING CURRENTS IS
EXPECTED TO CAUSE HUMBERTO TO MAKE A SHARP TURN TOWARD THE NORTH OR
NORTH-NORTHWEST IN 36-48 HOURS AND MAINTAIN THAT MOTION THROUGH 96
HOURS...AFTER WHICH THE RIDGE IS FORECAST TO RE-BUILD TO THE NORTH
OF THE CYCLONE AND TURN HUMBERTO WESTWARD OVER HIGHER LATITUDES AND
COOLER WATER. THE BULK OF THE MODEL GUIDANCE MADE A SIGNIFICANT
SHIFT TO THE EAST THIS CYCLE...AND THE OFFICIAL FORECAST TRACK WAS
SHIFTED TO THE RIGHT AS A RESULT...BUT NOT AS FAR TO THE RIGHT AS
SOME OF THE MORE RELIABLE MODELS LIKE THE GFS...ECMWF...AND FSSE.
 
MODEST NORTHEASTERLY SHEAR OF ABOUT 12 KT IS FORECAST BY ALL OF
MODELS TO WEAKEN TO LESS THAN 8 KT AND REMAIN LOW THROUGH AT LEAST
72 HOURS. SUCH WEAK SHEAR CONDITIONS EXISTING WITHIN A VERY MOIST
ENVIRONMENT AND OVER ABOVE AVERAGE SSTS OF AT LEAST 28C WOULD TEND
TO FAVOR SIGNIFICANT STRENGTHENING. IN FACT...THE GFS AND ECMWF
MODELS DEVELOP AN IMPRESSIVE 200 MB CYCLONIC OUTDRAFT PATTERN BY 72
HOURS...WHICH IS TYPICAL OF A MAJOR HURRICANE. AS A RESULT...THE
INTENSITY FORECAST WAS INCREASED OVER THE PREVIOUS ADVISORY AT 72
HOURS...SIMILAR TO THE ICON CONSENSUS MODEL. THE FORECAST REMAINS ON
THE CONSERVATIVE SIDE SINCE HUMBERTO WILL BE MOVING OVER SUB-26C
SSTS AT THAT TIME. IT IS POSSIBLE...HOWEVER...THAT HUMBERTO COULD
STRENGTHEN MORE THAN INDICATED PRIOR TO THE 72-HOUR TIME PERIOD. BY
DAYS 4 AND 5...INCREASING SOUTHWESTERLY SHEAR AND COOLER WATERS
SHOULD INDUCE GRADUAL WEAKENING.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  09/0900Z 13.4N  22.8W   35 KT  40 MPH
 12H  09/1800Z 13.6N  24.3W   45 KT  50 MPH
 24H  10/0600Z 14.1N  26.2W   55 KT  65 MPH
 36H  10/1800Z 14.9N  27.8W   60 KT  70 MPH
 48H  11/0600Z 16.2N  28.7W   70 KT  80 MPH
 72H  12/0600Z 20.0N  29.5W   80 KT  90 MPH
 96H  13/0600Z 23.5N  30.5W   70 KT  80 MPH
120H  14/0600Z 25.2N  33.4W   60 KT  70 MPH
 
$$
FORECASTER STEWART