ZCZC MIATCDEP4 ALL TTAA00 KNHC DDHHMM TROPICAL DEPRESSION FOUR-E DISCUSSION NUMBER 1 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP042008 800 PM PDT TUE JUL 01 2008 ASCAT DATA AT AROUND 16Z SHOWED THAT THE LOW PRESSURE AREA SOUTHWEST OF MANZANILLO MEXICO HAD A BROAD CENTER ELONGATED NORTH-NORTHWEST TO SOUTH-SOUTHEAST. SINCE THAT TIME...SATELLITE IMAGERY INDICATES THAT THE CIRCULATION AND ASSOCIATED SHOWER ACTIVITY HAS SOMEWHAT CONSOLIDATED AT THE SOUTHERN END OF THE ELONGATION. BASED ON THIS...ADVISORIES ARE INITIATED ON TROPICAL DEPRESSION FOUR-E. THE INITIAL INTENSITY IS 30 KT IN AGREEMENT WITH SATELLITE INTENSITY ESTIMATES FROM TAFB AND SAB...AS WELL AS THE OBSERVED WINDS IN THE EARLIER ASCAT DATA. THE INITIAL MOTION IS 315/6. THE DEPRESSION IS ON THE SOUTHWEST SIDE OF A WEAK MID-LEVEL RIDGE EXTENDING FROM THE SOUTHWESTERN UNITED STATES INTO MEXICO. THE LARGE-SCALE MODELS FORECAST THE RIDGE TO WEAKEN DURING THE NEXT 48-72 HR...WHICH RESULTS IN WEAK STEERING CURRENTS. THE ECMWF AND THE NOGAPS...WHICH KEEP THE CYCLONE ALIVE FOR 5 DAYS...FORECAST A SLOW NORTHWESTWARD MOTION FOR 48-72 HR AND A SLOW WESTWARD MOTION THEREAFTER. THIS IS SUPPORTED BY THE UKMET AND GFS UNTIL THEIR MODEL CYCLONES DISSIPATE NEAR 96 HR. THE FORECAST TRACK FOLLOWS THIS SCENARIO IN BEST AGREEMENT WITH THE ECMWF. THERE IS A CHANCE OF ERRATIC MOTION DURING THE FIRST 24 HR AS THE CYCLONE CONSOLIDATES. THE DEPRESSION IS CURRENTLY UNDER A LARGE UPPER-LEVEL ANTICYCLONE WITH WITH FAIR TO GOOD CIRRUS OUTFLOW IN ALL DIRECTIONS. THIS SHOULD ALLOW GRADUAL STRENGTHENING UNTIL THE CYCLONE REACHES COOLER SEA SURFACE TEMPERATURES IN 36-48 HR. THE GFS...ECMWF...AND NOGAPS FORECAST INCREASED VERTICAL WIND SHEAR AFTER 72-96 HR. SHOULD THIS VERIFY...THE SYSTEM COULD WEAKEN FASTER THAN CURRENTLY FORECAST. THE ASCAT DATA SHOWED 25-30 KT WINDS IN A BAND THAT IS CURRENTLY ABOUT 200 N MI FROM THE CENTER IN THE NORTHEASTERN QUADRANT. WHILE THE CENTER OF THE CYCLONE IS EXPECTED TO REMAIN WELL OFFSHORE... INTERESTS ALONG THE WEST COAST OF MEXICO FROM ZIHUATANEJO TO PUERTO VALLARTA SHOULD MONITOR ITS PROGRESS IN CASE IT COMES CLOSER THAN CURRENTLY FORECAST OR THE WIND FIELD IS LARGER THAN FORECAST. RAINBANDS ASSOCIATED WITH THE SYSTEM COULD AFFECT PORTIONS OF THE WESTERN COAST OF MEXICO TONIGHT AND WEDNESDAY. FORECAST POSITIONS AND MAX WINDS INITIAL 02/0300Z 15.9N 107.0W 30 KT 12HR VT 02/1200Z 16.4N 107.7W 35 KT 24HR VT 03/0000Z 17.0N 108.5W 40 KT 36HR VT 03/1200Z 17.5N 109.0W 45 KT 48HR VT 04/0000Z 18.0N 109.5W 40 KT 72HR VT 05/0000Z 19.0N 110.5W 35 KT 96HR VT 06/0000Z 19.5N 112.0W 30 KT 120HR VT 07/0000Z 19.5N 113.5W 25 KT $$ FORECASTER BEVEN NNNN
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