000 WTNT44 KNHC 181436 TCDAT4 TROPICAL STORM HUMBERTO DISCUSSION NUMBER 33 NWS NATIONAL HURRICANE CENTER MIAMI FL AL092013 1100 AM AST WED SEP 18 2013 HUMBERRTO APPEARS DISORGANIZED IN SATELLITE IMAGERY THIS MORNING. THE MOST CONCENTRATED CONVECTION IS IN BANDS LOCATED ABOUT 150 N MI EAST OF THE CENTER...WITH ONLY WIDELY SCATTERED CONVECTIVE CELLS NEAR THE CENTER. IN ADDITION...THE LOW-LEVEL CIRCULATION IS BECOMING ELONGATED FROM NORTH-NORTHWEST TO SOUTH-SOUTHEAST. WATER VAPOR AND AIRMASS IMAGERY SUGGESTS THE LOW-LEVEL CENTER IS STILL CLOSE TO AN UPPER-LEVEL LOW...WHICH MAY BE HINDERING THE CENTRAL CONVECTION. WHILE DVORAK SATELLITE ESTIMATES ARE BELOW TROPICAL STORM STRENGTH...AMSU-BASED INTENSITY ESTIMATES DURING THE NIGHT SUGGEST THE CYCLONE IS STILL A TROPICAL STORM. THE INITIAL INTENSITY IS THUS HELD...PERHAPS GENEROUSLY..AT 35 KT. VISIBLE IMAGERY HAS MADE IT EASIER TO FIND THE CENTER...WHICH IS A LITTLE FARTHER SOUTH THAN PREVIOUSLY ESTIMATED. THE INITIAL MOTION IS NOW 335/4. HUMBERTO IS EXPECTED TO TURN NORTHWARD DURING THE NEXT 12 HOURS OR SO...FOLLOWED BY AN ACCELERATION TOWARD THE NORTH-NORTHEAST AS THE CYCLONE ENTERS THE WESTERLIES. THE SPREAD OF THE TRACK MODEL GUIDANCE REMAINS FAIRLY NARROW...AND THE NEW TRACK FORECAST IS SIMILAR TO THE PREVIOUS FORECAST. THERE IS STILL TIME FOR HUMBERTO TO STRENGTHEN SOME AS IT MOVES INTO A MORE FAVORABLE UPPER-LEVEL WIND ENVIRONMENT NORTH OF THE UPPER-LEVEL LOW. HOWEVER...BY 48 HOURS THE CYCLONE SHOULD UNDERGO EXTRATROPICAL TRANSITION AS IT MERGES WITH A FRONTAL SYSTEM. THE NEW INTENSITY FORECAST IS THE SAME AS THE PREVIOUS FORECAST... CALLING FOR HUMBERTO TO BE A STORM-FORCE EXTRATROPICAL LOW BY 72 HOURS...AND THEN BE ABSORBED INTO ANOTHER LOW OVER THE NORTHEASTERN ATLANTIC. AN ALTERNATIVE SCENARIO...FAVORED BY THE GFS...ECMWF... AND CANADIAN MODELS...IS THAT LITTLE STRENGTHENING OCCURS AND THAT HUMBERTO DEGENERATES TO A TROUGH AS IT ENOUCNTERS THE FRONTAL SYSTEM. FORECAST POSITIONS AND MAX WINDS INIT 18/1500Z 31.3N 43.8W 35 KT 40 MPH 12H 19/0000Z 32.3N 43.8W 35 KT 40 MPH 24H 19/1200Z 33.8N 43.4W 40 KT 45 MPH 36H 20/0000Z 36.1N 42.1W 40 KT 45 MPH 48H 20/1200Z 38.7N 40.0W 45 KT 50 MPH...POST-TROP/EXTRATROP 72H 21/1200Z 51.0N 27.0W 50 KT 60 MPH...POST-TROP/EXTRATROP 96H 22/1200Z...ABSORBED $$ FORECASTER BEVEN