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| #371531 (Received by flhurricane at: 4:59 PM 26.Aug.2010) TCDAT2 TROPICAL STORM EARL DISCUSSION NUMBER 6 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL072010 500 PM AST THU AUG 26 2010 INNER-CORE CONVECTION REMAINS SHALLOW AND LOOSELY ORGANIZED...BUT THE OVERALL CLOUD PATTERN AND STRUCTURE HAS IMPROVED AND BECOME MORE CIRCULAR IN VISIBLE IMAGERY. AN 1150Z ASCAT PASS EARLIER THIS MORNING INDICATED EARL POSSESSED A LARGE SWATH OF 34-KT WINDS MORE THAN 90 NMI NORTH OF THE CENTER...WHICH WOULD SUPPORT HIGHER NEAR-SURFACE WINDS GIVEN THE LOW BIAS OF ASCAT WINDS. THE INITIAL INTENSITY WILL REMAIN 40 KT FOR THIS ADVISORY BASED ON A BLEND OF SATELLITE CURRENT INTENSITY ESTIMATES OF 45 KT AND 35 KT FROM TAFB AND SAB...RESPECTIVELY..AND THE AFOREMENTIONED ASCAT WINDS. EARL ALSO PASSED JUST NORTH OF PIRATA BUOY 13008 AROUND 1800Z...WHICH REPORTED A PRESSURE OF 1003 MB. THIS PRESSURE VALUE WOULD ALSO SUPPORT AN INTENSITY OF ABOUT 40 KT. EARL REMAINS ON TRACK WITH AN INITIAL MOTION ESTIMATE OF 280/16. THE OFFICIAL FORECAST TRACK REMAINS UNCHANGED THROUGH 48 HOURS AS THE STRONG SUBTROPICAL RIDGE TO THE NORTH REMAINS IN PLACE. BY 72 HOURS...EARL IS FORECAST TO APPROACH A WEAKNESS IN THE RIDGE AXIS INDUCED BY DANIELLE AND A MID-LATITUDE TROUGH THAT IS FORECAST TO HELP RECURVE THAT HURRICANE TO THE NORTHEAST. AS EARL APPROACHES THE WEAKNESS IN THE RIDGE...IT IS EXPECTED TO GRADUALLY SLOW DOWN AND TURN MORE TOWARD THE NORTHWEST. THE 12Z GFS AND ECMWF MODELS ARE NOW FORECASTING DANIELLE TO RECURVE TO THE NORTHEAST FASTER THAN PREVIOUSLY EXPECTED...WHICH ALSO ALLOWS THE SUBTROPICAL RIDGE BETWEEN EARL AND DANIELLE TO BUILD BACK IN TO THE NORTH OF EARL. THIS DEVELOPING FLOW PATTERN WOULD FORCE EARL MORE WESTWARD THAN NORTHWARD AT A SLOWER FORWARD SPEED BY DAYS 4 AND 5. THE OFFICIAL FORECAST TRACK IS JUST AN UPDATE OF THE PREVIOUS TRACK THROUGH 72 HOURS...AND THEN A LITTLE TO THE LEFT OF THE PREVIOUS ADVISORY AFTER THAT. THE FORECAST REMAINS ON THE NORTHERN OR RIGHT EDGE OF THE GUIDANCE ENVELOPE IN THE EVENT THE CIRCULATION CENTER REDEVELOPS FARTHER NORTH WITHIN THE BROAD CONVECTIVE CLOUD MASS. ALTHOUGH THE MODELS CONTINUE TO FORECAST LOW VERTICAL SHEAR ACROSS EARL THROUGH THE NEXT 24-36 HOURS...THE CYCLONE STILL HAS TO TRAVERSE THROUGH AN ENVIRONMENT OF DRY MID-LEVEL AIR. BY 48 HOURS...SOME OF THE NORTHERLY OUTFLOW ON THE EAST SIDE OF HURRICANE DANIELLE IS EXPECTED TO CREATE SOME MODEST NORTHERLY SHEAR ACROSS EARL...WHICH MAY INHIBIT THE DEVELOPMENT PROCESS. HOWEVER...BY DAYS 4 AND 5...THE UPPER-LEVEL FLOW PATTERN IS FORECAST TO BECOME MORE FAVORABLE FOR DEVELOPMENT AS EARL MOVES INTO THE SOUTHWEST PERIPHERY OF A LARGE SYNOPTIC-SCALE 200 MB ANTICYCLONE...WHICH SHOULD ACT TO ENHANCE THE OUTFLOW TO THE NORTH AND SOUTH OF THE CYCLONE. THE GFDL AND HWRF MODELS ARE ALSO INDICATING DEVELOPMENT OF THIS FAVORABLE OUTFLOW PATTERN AND STRENGTHEN EARL TO CATEGORY 4 INTENSITY BY 120 HOURS. THE OFFICIAL INTENSITY FORECAST IS A LITTLE LOWER THAN THE SHIPS AND LGEM MODELS THROUGH 72 HOURS AND THEN HIGHER AT DAYS 4 AND 5...BUT NOT AS HIGH AS THE GFDL/HWRF MODELS. FORECAST POSITIONS AND MAX WINDS INITIAL 26/2100Z 15.2N 38.8W 40 KT 12HR VT 27/0600Z 15.6N 41.2W 45 KT 24HR VT 27/1800Z 15.9N 44.4W 55 KT 36HR VT 28/0600Z 16.3N 47.7W 60 KT 48HR VT 28/1800Z 16.7N 50.8W 65 KT 72HR VT 29/1800Z 18.2N 55.9W 75 KT 96HR VT 30/1800Z 20.6N 60.0W 85 KT 120HR VT 31/1800Z 23.0N 62.5W 100 KT $$ FORECASTER STEWART |
