ZCZC MIATCDEP2 ALL TTAA00 KNHC DDHHMM TROPICAL STORM DALILA DISCUSSION NUMBER 7 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP072007 800 AM PDT MON JUL 23 2007 FIRST-LIGHT VISIBLE IMAGERY SHOWS THAT THE CENTER OF DALILA IS EXPOSED BETWEEN TWO LARGE...BUT DISORGANIZED...CONVECTIVE MASSES. SATELLITE INTENSITY ESTIMATES FROM TAFB AND SAB REMAIN 35 KT...AND THAT REMAINS THE INITIAL INTENSITY. ANALYSES FROM CIMSS AT THE UNIVERSITY OF WISCONSIN INDICATE CONTINUING 20-25 KT NORTHEASTERLY VERTICAL WIND SHEAR. SO FAR THOUGH...THE LARGE SIZE OF DALILA'S CYCLONIC CIRCULATION HAS HELPED IT STAND UP TO THE SHEAR. THE CENTER OF DALILA IS NORTH OF THE PREVIOUS ADVISORY POSITION... AND THE INITIAL MOTION IS NOW ESTIMATED AT 315/9. DALILA REMAINS SOUTH OF A WEAK MID-LEVEL RIDGE OF HIGH PRESSURE OVER NORTHWESTERN MEXICO...WITH A MID-LEVEL TROUGH OVER NORTHEASTERN MEXICO. THE LARGE-SCALE MODELS FORECAST THE TROUGH TO MOVE WEST-SOUTHWESTWARD TO THE NORTH OF DALILA...WHICH WOULD WEAKEN THE STEERING CURRENTS AND ALLOW A MORE NORTHWARD MOTION. THE ECMWF HAS THE STRONGEST DEPICTION OF THE TROUGH AND THUS HAS THE SHARPEST NORTHWARD TURN AND THE MOST EASTWARD FORECAST TRACK...WHILE THE GFS ENSEMBLE MEAN HAS THE WEAKEST DEPICTION AND THE MOST WESTWARD FORECAST TRACK. IT SHOULD BE NOTED THAT EVEN THE ECMWF DOES NOT BRING DALILA OVER BAJA CALIFORNIA...AS THE RIDGE TO THE NORTH RE-BUILDS BEHIND THE TROUGH AND FORCES THE CYCLONE NORTHWESTWARD WITH SOME INCREASE IN FORWARD SPEED AFTER 72 HR. THE NEW FORECAST TRACK IS ADJUSTED TO THE EAST OF THE PREVIOUS TRACK BASED ON THE INITIAL POSITION AND MOTION. THE TRACK IS DOWN THE MIDDLE OF THE ENVELOPE OF MODEL GUIDANCE IN GOOD AGREEMENT WITH THE NOGAPS AND THE SUPERENSEMBLE. THE LARGE-SCALE MODELS AGREE THAT THE SHEAR WILL ABATE IN ABOUT 24 HR. SHOULD THIS VERIFY...THIS WOULD ALLOW DALILA TO INTENSIFY AT A FASTER RATE THAN IT HAS DONE SO FAR. THE GFDL AND SHIPS MODELS FORECAST A PEAK INTENSITY OF 60 KT...WITH THE GFDL REACHING IT IN 36 HR AND THE SHIPS IN 60 HR. THE INTENSITY FORECAST CALLS FOR SLOW DEVELOPMENT FOR 24 HR...THEN FASTER INTENSIFICATION TO 60 KT BY 48 HR AS THE SHEAR DECREASES. AFTER 72 HR...DALILA SHOULD MOVE OVER COLDER SEA SURFACE TEMPERATURES AND WEAKEN. IT CANNOT BE RULED OUT THAT DALILA COULD BECOME A HURRICANE. HOWEVER...EVEN AFTER THE SHEAR DECREASES THE STORM HAS WORK TO DO TO OVERCOME ITS INTERNAL DISORGANIZATION. FORECAST POSITIONS AND MAX WINDS INITIAL 23/1500Z 14.8N 108.9W 35 KT 12HR VT 24/0000Z 15.5N 109.7W 40 KT 24HR VT 24/1200Z 16.2N 110.4W 45 KT 36HR VT 25/0000Z 17.0N 111.1W 50 KT 48HR VT 25/1200Z 18.1N 112.1W 60 KT 72HR VT 26/1200Z 20.0N 114.5W 60 KT 96HR VT 27/1200Z 22.0N 117.5W 50 KT 120HR VT 28/1200Z 23.5N 121.0W 35 KT $$ FORECASTER BEVEN NNNN
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Page last modified: Friday, 02-Nov-2007 21:20:59 UTC