760 
 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