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| #101565 (Received by flhurricane at: 5:00 PM 01.Aug.2006) TCDAT3 TROPICAL STORM CHRIS DISCUSSION NUMBER 4 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL032006 500 PM EDT TUE AUG 01 2006 ON THE FIRST AIRCRAFT MISSION INTO CHRIS...THE AIR FORCE RESERVE UNIT HURRICANE HUNTERS FOUND A VERY SMALL CORE OF STRONG WINDS WITH A CENTRAL PRESSURE OF 1007 MB. THIS IS ACTUALLY A RATHER LOW PRESSURE CONSIDERING THE HIGH ENVIRONMENTAL BAROMETER READINGS. MAXIMUM FLIGHT LEVEL WINDS WERE 53 KT JUST TO THE SOUTHEAST OF THE CENTER. BASED ON THE STANDARD 80 PERCENT REDUCTION FROM THE 1000 FT FLIGHT LEVEL THE CURRENT INTENSITY IS SET AT 40 KT. THE ENVIRONMENT IS RELATIVELY STABLE...SOME NORTH-NORTHWESTERLY VERTICAL SHEAR IS IMPACTING THE SYSTEM...AND THE GLOBAL MODELS CONTINUE TO FORECAST WEAKENING. HOWEVER...THERE IS A WELL-MARKED UPPER-TROPOSPHERIC OUTFLOW CHANNEL EMANATING WEST-SOUTHWESTWARD FROM CHRIS...AND A FAIR AMOUNT OF OUTFLOW IS ALSO EVIDENT OVER THE EASTERN QUADRANT. THIS DIVERGENCE ALOFT COULD ALLOW ADDITIONAL INTENSIFICATION. ADDITIONALLY THE GFDL MODEL FORECASTS STRENGTHENING UNTIL THE MODELED CIRCULATION INTERACTS WITH HISPANIOLA. THE OFFICIAL FORECAST CLOSELY FOLLOWS THE SHIPS GUIDANCE...WHICH DOES SHOW A SLIGHT DECREASE IN VERTICAL SHEAR AFTER A COUPLE OF DAYS. A MID-TROPOSPHERIC RIDGE EXISTS TO THE NORTH OF CHRIS WITH A MID- TO UPPER-LEVEL WEAKNESS IN THE VICINITY OF 70W LONGITUDE. THE TROUGH NEAR 70W IS FORECAST TO SHIFT WESTWARD WITH TIME SO THAT THE RIDGE TO THE NORTH OF THE TROPICAL CYCLONE IS MAINTAINED...OR EVEN STRENGTHENED. DYNAMICAL GUIDANCE MODEL TRACKS HAVE BEEN GRADUALLY SHIFTING TO THE LEFT OVER THE LAST COUPLE OF RUNS...MOST LIKELY IN RESPONSE TO A BUILDING RIDGE. THE OFFICIAL FORECAST IS THEREFORE ADJUSTED A LITTLE TO THE LEFT OF THAT FROM THE PREVIOUS PACKAGE. THIS IS NORTH OF THE LATEST DYNAMICAL CONSENSUS AND THE FSU SUPERENSEMBLE TRACK. A TROPICAL STORM WARNING HAS BEEN ISSUED FOR PUERTO RICO AND THE U.S. AND BRITISH VIRGIN ISLANDS. THE TROPICAL STORM WARNING FOR THE NORTHERN LEEWARDS IS MAINTAINED AT THIS TIME. IT SHOULD BE NOTED THAT...EVEN IF THE CENTER OF CHRIS PASSES JUST TO THE NORTH OF SOME OF THESE ISLANDS...RATHER STRONG WINDS COULD BE EXPERIENCED IN THE ISLANDS DUE TO RAIN BANDS OVER THE SOUTHERN SEMICIRCLE OF THE STORM. IN FACT AT THIS TIME IT APPEARS THAT THE HEAVIEST WEATHER IS OCCURRING OVER THE SOUTHERN PORTION OF THE CIRCULATION. FORECAST POSITIONS AND MAX WINDS INITIAL 01/2100Z 17.7N 61.2W 40 KT 12HR VT 02/0600Z 18.3N 62.6W 45 KT 24HR VT 02/1800Z 19.1N 64.5W 45 KT 36HR VT 03/0600Z 19.9N 66.6W 50 KT 48HR VT 03/1800Z 20.5N 68.7W 50 KT 72HR VT 04/1800Z 21.5N 73.0W 50 KT 96HR VT 05/1800Z 22.5N 77.0W 55 KT 120HR VT 06/1800Z 23.5N 80.5W 55 KT |
