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| #111175 (Received by flhurricane at: 10:49 AM 16.Sep.2006) TCDAT3 HURRICANE HELENE DISCUSSION NUMBER 17 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082006 1100 AM EDT SAT SEP 16 2006 GEOSTATIONARY SATELLITE IMAGERY INDICATES INCREASING ORGANIZATION OF HELENE WITH ROBUST BANDING CONVECTION ON THE NORTH AND WEST QUADRANTS...AND A RAGGED EYE ATTEMPTING TO FORM AS SEEN IN THE VISIBLE IMAGERY. MOREOVER...SSMI AND AMSU PASSES SHOW A NEARLY COMPLETE EYEWALL. BASED UPON CONSENSUS OF DVORAK ESTIMATES...THE SYSTEM IS UPGRADED TO A 65 KT HURRICANE. WHILE A SAHARAN AIR-LAYER IS SEEN TO THE NORTH AND WEST OF HELENE IN CIMSS IMAGERY...TOTAL PRECIPITABLE WATER ANALYSES FROM CIRA SUGGEST THAT THE DRY AIR REMAINS AT LEAST A COUPLE HUNDRED MILES FROM THE CENTER OF THE SYSTEM. CONTINUED SLOW INTENSIFICATION IS SUGGESTED OVER THE NEXT THREE DAYS DUE TO 27.5 C SSTS...LIGHT/MODERATE VERTICAL SHEAR...AND A MOIST ENVIRONMENT. AT DAYS 4 AND 5...THE SSTS WARM UP...BUT SHEAR INCREASES MAY MITIGATE FURTHER INTENSIFICATION. A PLATEAUING OF THE INTENSITY IS CALLED FOR AROUND 72 HRS WITH SLIGHT WEAKENING THEREAFTER. THE INTENSITY FORECAST IS A BLEND OF THE SHIPS...FSU SUPER-ENSEMBLE...AND GFDL MODELS...WHICH IS SLIGHTLY WEAKER THAN PREVIOUSLY PREDICTED AT THE LONG-LEADS. CURRENT MOTION ESTIMATE IS 305/12. HELENE IS ON THE SOUTHWEST SIDE OF A DEEP-LAYER RIDGE AND IS HEADED TOWARD A BREAK IN THE RIDGE... WHICH IS PARTIALLY BEING PRODUCED BY HURRICANE GORDON. ALL RELIABLE GUIDANCE IS IN CLOSE AGREEMENT WITH A CONTINUED MOVEMENT ALONG THIS HEADING THROUGH 72 HR. AT DAYS 4 AND 5...THERE IS A SIGNIFICANT MODEL DIVERGENCE WITH THE UK...GFDL...ECMWF BEING FASTER AND OFF TO THE NORTH AND THE GFS AND GFS ENSEMBLE SLOWER AND OFF TO THE SOUTH. THESE DIFFERENCES ARE BEING DRIVEN BY THE AMPLITUDE OF THE SHORT-WAVE TROUGH THAT WILL BE PUSHING OFF OF THE US EAST COAST AT THAT TIME. THE NOGAPS AND CONSENSUS MODELS ARE IN BETWEEN THESE POSSIBILITIES. THE TRACK FORECAST IS CLOSE TO THE CONSENSUS MODELS AND SLIGHTLY SLOWER AND TO THE RIGHT OF THE PREVIOUS PREDICTION. A G-IV AIRCRAFT RESEARCH MISSION IS CURRENTLY ENROUTE TO SAMPLE HELENE'S ENVIRONMENT AS PART OF NOAA'S SALEX EXPERIMENT. FORECAST POSITIONS AND MAX WINDS INITIAL 16/1500Z 18.8N 45.6W 65 KT 12HR VT 17/0000Z 19.5N 46.9W 70 KT 24HR VT 17/1200Z 20.4N 48.3W 75 KT 36HR VT 18/0000Z 21.1N 49.4W 80 KT 48HR VT 18/1200Z 21.9N 50.6W 85 KT 72HR VT 19/1200Z 23.5N 53.5W 90 KT 96HR VT 20/1200Z 25.5N 56.5W 85 KT 120HR VT 21/1200Z 28.5N 58.0W 80 KT $$ FORECASTER BEVEN/LANDSEA |
