ZCZC MIATCDEP2 ALL TTAA00 KNHC DDHHMM TROPICAL STORM GUILLERMO DISCUSSION NUMBER 6 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 2 PM PDT FRI AUG 08 2003 GUILLERMO HAS SHOWN MIXED SIGNALS DURING THE DAY. ON ONE SIDE... SSM/I DATA RECEIVED SINCE THE LAST ADVISORY SHOWS TIGHTLY CURVED CONVECTIVE BANDS AND A POSSIBLE EYE. ON THE OTHER HAND...THE CLOUD PATTERN IN VISIBLE IMAGERY HAS DECAYED SOMEWHAT THIS AFTERNOON... POSSIBLY DUE TO SOME WEAK SOUTHERLY SHEAR CAUSED BY AN UPPER-LEVEL LOW NEAR 17N125W. SATELLITE INTENSITY ESTIMATES ARE 55 KT FROM TAFB...45 KT FROM SAB...AND 35 KT FROM AFWA. BASED ON THESE AND THE POSSIBLE EYE...THE MAXIMUM WINDS ARE INCREASED TO 50 KT. THE MICROWAVE DATA INDICATES THAT THE CENTER IS ABOUT A HALF DEGREE SOUTH OF THE PREVIOUS ADVISORY POSITION. IT IS UNCLEAR WHETHER THIS COMES FROM MOTION OR REFORMATION OF THE CENTER...SO THE INITIAL MOTION IS AN UNCERTAIN 250/7. OTHER THAN THIS...THERE IS LITTLE CHANGE IN EITHER THE SYNOPTIC PATTERN OF THE FORECAST PHILOSOPHY FROM THE PREVIOUS PACKAGE. GUILLERMO IS ON THE SOUTH SIDE OF A LOW/MID-LEVEL RIDGE...WHICH SHOULD PERSIST DURING THE FORECAST PERIOD. THIS SHOULD KEEP THE STORM ON A GENERAL WESTWARD COURSE THROUGH THE FORECAST PERIOD. NHC TRACK GUIDANCE STILL AGREES WITH THIS SCENARIO...ALTHOUGH A FAIR AMOUNT OF SPREAD IN THE SPEED REMAINS. THE OFFICIAL FORECAST IS ALMOST PARALLEL TO THE PREVIOUS TRACK...BUT IS SHIFTED ABOUT A DEGREE SOUTHWARD BASED ON CURRENT TRENDS. THE FORECAST IS IN BEST AGREEMENT WITH THE NOGAPS. THE ABOVE BEING SAID...THERE IS AN ALTERNATIVE TRACK FORECAST POSSIBILITY. AN AREA OF DISTURBED WEATHER CENTERED NEAR 13N107W IS WEAKER...BUT LARGER THAN GUILLERMO. THERE IS A SLIGHT CHANCE THAT THE TWO SYSTEMS COULD INTERACT...AND SUCH AN INTERACTION COULD CAUSE A DIFFERENT TRACK FOR GUILLERMO THAN CURRENTLY FORECAST. THERE ARE NO SIGNS OF THIS YET. LARGE-SCALE MODELS NOW SUGGEST THAT THE CURRENTLY SOUTHERLY SHEAR COULD PERSIST FOR 24 HR OR MORE AS THE UPPER-LEVEL LOW NORTHWEST OF GUILLERMO MOVES WESTWARD ALONG WITH THE STORM. HOWEVER...THE SHIPS MODEL DOES NOT FORECAST ENOUGH SHEAR TO KEEP THE SYSTEM FROM STRENGTHENING...AND THE GFDL STRENGTHENS IT AS WELL. THE INTENSITY FORECAST WILL BE BASED ON THE PREMISE THAT THE SHEAR WILL ONLY SLOW THE DEVELOPMENT AND FORECASTS THE STORM TO REACH 60 KT IN 36-48 HR. WHILE THE MORE SOUTHERLY TRACK KEEPS THE STORM IN WARMER WATER THAN THE PREVIOUS TRACK...AFTER 72 HR GUILLERMO SHOULD COME CLOSE ENOUGH TO COOLER WATER TO SLOWLY WEAKEN. FORECASTER BEVEN FORECAST POSITIONS AND MAX WINDS INITIAL 08/2100Z 16.0N 119.6W 50 KT 12HR VT 09/0600Z 15.9N 120.7W 50 KT 24HR VT 09/1800Z 15.9N 122.8W 55 KT 36HR VT 10/0600Z 15.9N 125.1W 60 KT 48HR VT 10/1800Z 16.0N 127.4W 60 KT 72HR VT 11/1800Z 16.0N 131.5W 55 KT 96HR VT 12/1800Z 16.0N 135.5W 55 KT 120HR VT 13/1800Z 16.0N 139.5W 50 KT NNNN
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Page last modified: Monday, 07-Feb-2005 16:49:56 UTC