TROPICAL STORM BONNIE DISCUSSION NUMBER 4
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL032010
500 AM EDT FRI JUL 23 2010

THE AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT INVESTIGATING BONNIE HAS FOUND LITTLE CHANGE IN STRENGTH.

THE AIRCRAFT HAS MEASURED A PEAK 850 MB FLIGHT-LEVEL WIND OF 42 KT…BELIEVABLE SFMR WINDS OF 34 KT…AND A MINIMUM PRESSURE OF 1008 MB.

THESE DATA SUPPORT MAINTAINING AN INITIAL INTENSITY OF 35 KT.

THE AIRCRAFT DATA SUGGEST THAT THE CIRCULATION HAS BECOME LESS DEFINED AS FEW WEST OR NORTHWEST WINDS WERE FOUND.

IF THIS TREND CONTINUES…IT IS POSSIBLE FOR BONNIE TO DEGENERATE TO AN OPEN TROUGH.

FOR NOW…THE OFFICIAL FORECAST ASSUMES THAT BONNIE WILL BE ABLE TO MAINTAIN A CLOSED CIRCULATION AND REMAIN A TROPICAL CYCLONE.

AS BONNIE PASSED THROUGH THE CENTRAL BAHAMAS…AN OBSERVING SITE ON STANIEL CAY REPORTED A SUSTAINED WIND OF 37 KT.

THE AIRCRAFT FIXES SHOW THAT BONNIE IS MOVING FASTER AND HAS TURNED WEST-NORTHWESTWARD. THE INITIAL MOTION ESTIMATE IS 295/16.

BONNIE IS FORECAST TO MAINTAIN THIS GENERAL HEADING DURING THE NEXT DAY OR SO AS IT MOVES AROUND THE SOUTHWESTERN SIDE OF A MID- TO UPPER-LEVEL RIDGE CENTERED OVER THE CAROLINAS.

THE TRACK GUIDANCE IS GOOD AGREEMENT DURING FIRST 48 HOURS…BUT THERE IS SOME SPREAD IN THE GUIDANCE AFTER LANDFALL ALONG THE NORTHERN GULF COAST.

THE GUIDANCE IS NOTICEABLY FASTER…WHICH MAY BE IN PART FROM THE MORE WESTWARD INITIAL LOCATION.

THE NEW NHC TRACK IS SIMILAR TO THE PREVIOUS TRACK BUT IS FASTER THAN THE PREVIOUS ADVISORY.

THIS REQUIRES THE ISSUANCE OF TROPICAL STORM WATCHES FOR A PORTION OF THE NORTHERN GULF COAST.

THE UPPER-AIR ENVIRONMENT AHEAD OF BONNIE IS LESS THAN IDEAL FOR STRENGTHENING.

TROPICAL STORM BONNIE IS EXPECTED TO REMAIN UNDER THE INFLUENCE OF MODERATE TO STRONG SOUTHEASTERLY SHEAR DUE TO THE FLOW BETWEEN AN UPPER-LEVEL LOW OVER THE GULF OF MEXICO AND THE AFOREMENTIONED RIDGE.

THE UPPER-LEVEL FLOW IS FORECAST BY THE GLOBAL MODELS TO WEAKEN IN 36-48 HOURS…WHICH COULD ALLOW FOR SOME STRENGTHENING OF BONNIE.

THE OFFICIAL FORECAST IS BETWEEN THE MORE AGGRESSIVE SHIPS/LGEM GUIDANCE AND THE HWRF/GFDL MODELS WHICH SHOWS LITTLE…IF ANY…INTENSIFICATION.

TROPICAL STORM BONNIE FORECAST POSITIONS AND MAX WINDS

INITIAL 23/0900Z 24.1N 78.6W 35 KT
12HR VT 23/1800Z 25.0N 81.0W 40 KT
24HR VT 24/0600Z 26.2N 84.1W 40 KT
36HR VT 24/1800Z 27.6N 86.9W 45 KT
48HR VT 25/0600Z 28.8N 89.1W 45 KT
72HR VT 26/0600Z 31.5N 92.0W 25 KT…INLAND
96HR VT 27/0600Z 34.5N 93.0W 20 KT…POST-TROP/REMNT LOW
120HR VT 28/0600Z…DISSIPATED

A TROPICAL STORM WATCH HAS BEEN ISSUED FOR THE EAST COAST OF FLORIDA FROM NORTH OF GOLDEN BEACH TO JUPITER INLET INCLUDING LAKE OKEECHOBEE.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT…

A TROPICAL STORM WARNING IS IN EFFECT FOR…
* CENTRAL AND NORTHWESTERN BAHAMAS
* FOR THE FLORIDA EAST COAST FROM GOLDEN BEACH SOUTHWARD INCLUDING THE ENTIRE FLORIDA KEYS AND FLORIDA BAY…AND ALONG THE WEST COAST OF FLORIDA NORTHWARD TO BONITA BEACH

A TROPICAL STORM WATCH IN IN EFFECT FOR…
* THE EAST COAST OF FLORIDA NORTH OF GOLDEN BEACH TO JUPITER INLET INCLUDING LAKE OKEECHOBEE

A TROPICAL STORM WARNING MEANS THAT TROPICAL STORM CONDITIONS ARE EXPECTED SOMEWHERE WITHIN THE WARNING AREA WITHIN 36 HOURS.

A TROPICAL STORM WATCH MEANS THAT TROPICAL STORM CONDITIONS ARE POSSIBLE WITHIN THE WATCH AREA…GENERALLY WITHIN 48 HOURS.

TROPICAL DEPRESSION CENTER LOCATED NEAR 21.9N 75.0W AT 22/1500Z POSITION ACCURATE WITHIN 60 NM

PRESENT MOVEMENT TOWARD THE WEST-NORTHWEST OR 295 DEGREES AT 13 KT

ESTIMATED MINIMUM CENTRAL PRESSURE 1008 MB MAX SUSTAINED WINDS 30 KT WITH GUSTS TO 40 KT.
12 FT SEAS..200NE 0SE 0SW 0NW.
WINDS AND SEAS VARY GREATLY IN EACH QUADRANT. RADII IN NAUTICAL MILES ARE THE LARGEST RADII EXPECTED ANYWHERE IN THAT QUADRANT.

REPEAT…CENTER LOCATED NEAR 21.9N 75.0W AT 22/1500Z
AT 22/1200Z CENTER WAS LOCATED NEAR 21.6N 74.4W

FORECAST VALID 23/0000Z 22.6N 76.8W
MAX WIND 35 KT…GUSTS 45 KT.
34 KT… 90NE 50SE 0SW 25NW.

FORECAST VALID 23/1200Z 23.8N 80.0W
MAX WIND 40 KT…GUSTS 50 KT.
34 KT… 90NE 50SE 0SW 25NW.

FORECAST VALID 24/0000Z 25.0N 83.2W
MAX WIND 40 KT…GUSTS 50 KT.
34 KT… 90NE 50SE 0SW 25NW.

FORECAST VALID 24/1200Z 26.0N 86.5W
MAX WIND 40 KT…GUSTS 50 KT.
34 KT… 90NE 50SE 0SW 25NW.

FORECAST VALID 25/1200Z 28.0N 91.5W
MAX WIND 45 KT…GUSTS 55 KT.
34 KT… 90NE 50SE 0SW 25NW.

EXTENDED OUTLOOK. NOTE…ERRORS FOR TRACK HAVE AVERAGED NEAR 200 NM ON DAY 4 AND 250 NM ON DAY 5…AND FOR INTENSITY NEAR 20 KT EACH DAY

OUTLOOK VALID 26/1200Z 31.0N 94.0W…INLAND MAX WIND 25 KT…GUSTS 35 KT.

OUTLOOK VALID 27/1200Z 33.0N 95.0W…POST-TROP/REMNT LOW MAX WIND 20 KT…GUSTS 25 KT.

REQUEST FOR 3 HOURLY SHIP REPORTS WITHIN 300 MILES OF 21.9N 75.0W

NEXT ADVISORY AT 22/2100Z

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FORECASTER AVILA