16/0500 EDT - WTNT45 KNHC 160832 TCDAT5 TROPICAL STORM ERIN DISCUSSION NUMBER 6 NWS NATIONAL HURRICANE CENTER MIAMI FL AL052013 500 AM AST FRI AUG 16 2013 ERIN REMAINS DISORGANIZED THIS MORNING...WITH THE LOW-LEVEL CENTER PARTLY EXPOSED TO THE NORTHWEST OF THE MAIN CONVECTIVE CLUSTER. SATELLITE INTENSITY ESTIMATES ARE 35 KT FROM TAFB AND 30 KT FROM SAB...AND A CIMSS AMSU ESTIMATE NEAT 0400 UTC WAS 31 KT. THE INITIAL INTENSITY REMAINS 35 KT FOR THIS ADVISORY. THE INITIAL MOTION IS 295/14. ERIN IS CURRENTLY BEING STEERED BY A LOW/MID-LEVEL RIDGE TO THE NORTH AND NORTHEAST. THE GLOBAL MODELS FORECAST THIS RIDGE TO STRENGTHEN DURING THE NEXT 2-3 DAYS AS MID/UPPER-LEVEL LOW SOUTH OF THE AZORES MOVES OFF TO THE NORTHEAST. THE TRACK GUIDANCE IS IN FAIRLY GOOD AGREEMENT THAT ERIN WILL CONTINUE WEST-NORTHWESTWARD FOR 36-48 HR...THEN TURN MORE WESTWARD AS THE CYCLONE BECOME SHALLOWER AND STEERED MORE BY THE LOW-LEVEL FLOW. SUBSEQUENTLY...THE GFS...UKMET...CANADIAN...AND NAVGEM MODELS FORECAST A SECOND WEAKNESS TO DEVELOP IN THE RIDGE BETWEEN 50W-60W BY 120 HOURS...WHICH WOULD ALLOW ERIN TO TURN MORE NORTHWARD. THE TRACK GUIDANCE ENVELOPE HAS AGAIN SHIFTED TO THE NORTH...AND THE NEW TRACK FORECAST IS LIKEWISE SHIFTED NORTH OF THE PREVIOUS FORECAST. HOWEVER...THE NEW TRACK IS STILL SOUTH OF THE MODEL CONSENSUS. WHILE ERIN IS CURRENTLY IN A LIGHT VERTICAL WIND SHEAR ENVIRONMENT...THE CYCLONE IS CURRENTLY OVER SEA SURFACE TEMPERATURES OF 25C-26C...AND METEOSAT AIRMASS IMAGERY SUGGESTS THE CYCLONE IS APPROACHING AN AREA OF DRIER AIR. THE INTENSITY GUIDANCE NOW FORECASTS SHORT-TERM INTENSIFICATION THAN 6 HOURS AGO...AND THUS THE NEW INTENSITY FORECAST IS REDUCED FROM THAT OF THE PREVIOUS ADVISORY. IN THE LONG TERM...AFTER 72 HOURS...ERIN IS FORECAST TO REACH INCREASING SEA SURFACE TEMPERATURES. HOWEVER... IT IS ALSO EXPECTED TO ENCOUNTER INCREASING SOUTHWESTERLY SHEAR AND MORE DRY AIR. THE INTENSITY FORECAST IS THE SAME AS THE PREVIOUS FORECAST IN SHOWING WEAKENING DURING THIS TIME. AN ALTERNATIVE FORECAST SCENARIO IS THAT ERIN DEGENERATES TO A TROPICAL WAVE BEFORE 120 HOURS...AS FORECAST BY ALL OF THE GLOBAL MODELS EXCEPT THE GFS. FORECAST POSITIONS AND MAX WINDS INIT 16/0900Z 16.3N 30.5W 35 KT 40 MPH 12H 16/1800Z 17.3N 32.4W 35 KT 40 MPH 24H 17/0600Z 18.6N 34.7W 40 KT 45 MPH 36H 17/1800Z 19.6N 36.7W 40 KT 45 MPH 48H 18/0600Z 20.3N 38.7W 40 KT 45 MPH 72H 19/0600Z 21.0N 43.0W 40 KT 45 MPH 96H 20/0600Z 22.5N 47.5W 35 KT 40 MPH 120H 21/0600Z 24.5N 51.0W 30 KT 35 MPH $$ FORECASTER BEVEN
Posted on: Fri, 16 Aug 2013 08:35:53 +0000
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