BULLETIN
HURRICANE BERTHA ADVISORY NUMBER 30
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL022008
11:00 AM AST THU JUL 10 2008
WEAKER BERTHA MOVING NORTHWESTWARD. SWELLS NOW AFFECTING
BERMUDA... IT IS STILL TOO EARLY TO DETERMINE THE EXTENT TO WHICH BERTHA
COULD IMPACT BERMUDA. INTERESTS ON THAT ISLAND SHOULD CLOSELY MONITOR THE
PROGRESS OF BERTHA DURING THE NEXT SEVERAL DAYS. FOR STORM INFORMATION
SPECIFIC TO YOUR AREA, INCLUDING POSSIBLE INLAND WATCHES AND WARNINGS,
PLEASE MONITOR PRODUCTS ISSUED BY YOUR LOCAL WEATHER OFFICE.
AT 11:00 AM AST, 1500Z, THE CENTER OF HURRICANE BERTHA WAS LOCATED NEAR
LATITUDE 26.5 NORTH, LONGITUDE 60.2 WEST, OR ABOUT 485 MILES, 785 KM
SOUTHEAST OF BERMUDA. BERTHA IS MOVING TOWARD THE NORTHWEST NEAR 9 MPH, 15
KM HR. A GRADUAL TURN TOWARD THE NORTH AND A DECREASE IN FORWARD SPEED ARE
EXPECTED DURING THE NEXT COUPLE OF DAYS.
MAXIMUM SUSTAINED WINDS HAVE DECREASED TO NEAR 90 MPH, 150 KM HR, WITH
HIGHER GUSTS, MAKING BERTHA A CATEGORY ONE HURRICANE ON THE SAFFIR-SIMPSON
SCALE. WHILE BERTHA HAS WEAKENED THIS MORNING, IT COULD RE-INTENSIFY DURING
THE NEXT 24 HOURS. HURRICANE FORCE WINDS EXTEND OUTWARD UP TO 30 MILES, 45
KM FROM THE CENTER, AND TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 140
MILES, 220 KM. ESTIMATED MINIMUM CENTRAL PRESSURE IS 977 MB, 28.85 INCHES.
LARGE SWELLS AND HIGH SURF HAVE STARTED TO AFFECT BERMUDA. THESE CONDITIONS
ARE EXPECTED TO PERSIST FOR THE NEXT FEW DAYS.
REPEATING THE 11:00 AM AST POSITION, 26.5 N, 60.2 W. MOVEMENT TOWARD,
NORTHWEST NEAR 9 MPH. MAXIMUM SUSTAINED WINDS, 90 MPH. MINIMUM CENTRAL
PRESSURE, 977 MB. THE NEXT ADVISORY WILL BE ISSUED BY THE NATIONAL HURRICANE
CENTER AT 5:00 PM AST.
HURRICANE BERTHA DISCUSSION NUMBER 30
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL022008
11:00 AM EDT THU JUL 10 2008
SATELLITE IMAGERY INDICATES THAT THE EYE OF BERTHA HAS BECOME SOMEWHAT
RAGGED THIS MORNING, AND THE CONVECTIVE TOPS IN THE EYE WALL HAVE WARMED.
THIS HAS RESULTED IN THE SATELLITE INTENSITY ESTIMATES FROM TAFB AND SAB
DECREASING TO 77 KT. THE INITIAL INTENSITY IS REDUCED TO 80 KT, AND THIS
COULD BE A LITTLE GENEROUS. ALTHOUGH BERTHA HAS WEAKENED, THE OUTER BANDING
HAS INCREASED DURING THE NIGHT AND NOW SURROUNDS THE EYE AND CENTRAL DENSE
OVERCAST. THE CIRRUS OUTFLOW IS FAIR TO GOOD IN ALL DIRECTIONS EXCEPT THE
SOUTHEAST, WHERE IT IS POOR TO NON-EXISTENT.
THE INITIAL MOTION REMAINS 315/8. BERTHA IS ON THE SOUTH SIDE OF A
MID-LEVEL ANTICYCLONE SEEN IN WATER VAPOR IMAGERY NEAR 37N59W. THE
ANTICYCLONE WILL WEAKEN AS A MID/UPPER-LEVEL SHORTWAVE TROUGH OVER THE
NORTHEASTERN UNITED STATES MOVES INTO THE ATLANTIC DURING THE NEXT 24-36
HOURS. THIS PATTERN EVOLUTION SHOULD CAUSE BERTHA TO TURN NORTHWARD. THE
SHORTWAVE TROUGH IS FORECAST TO PASS NORTH OF BERTHA, AND FROM 36-72 HR THE
LARGE-SCALE MODELS FORECAST A MID-LEVEL RIDGE TO BUILD NORTH OF THE
HURRICANE IN THE WAKE OF THE TROUGH. THE TRACK MODELS RESPOND TO THIS BY
FORECASTING ERRATIC MOTION AS BERTHA APPROACHES BERMUDA. THE NEW FORECAST
TRACK WILL CALL FOR A SLOW NORTHWARD MOTION DURING THIS TIME AS A COMPROMISE
BETWEEN THE VARIOUS TWISTS AND TURNS OF THE TRACK GUIDANCE.
HOWEVER, THERE IS A POSSIBILITY THAT BERTHA COULD JOG LEFT OF THE FORECAST
TRACK CLOSER TO BERMUDA AS SHOWN BY THE GFS, UKMET AND CANADIAN MODELS.
AFTER 72 HR, A SECOND MID/UPPER-LEVEL TROUGH MOVING INTO THE WESTERN
ATLANTIC SHOULD WEAKEN THE RIDGE, WHICH SHOULD CAUSE BERTHA TO MOVE SOMEWHAT
FASTER TOWARD THE NORTH.
THE INTENSITY FORECAST IS A CONUNDRUM. THE LARGE-SCALE MODELS FORECAST A
LARGE UPPER-LEVEL ANTICYCLONE TO DEVELOP OVER BERTHA DURING THE NEXT 24-48
HR WHILE THE SYSTEM IS STILL OVER WARM WATER. THIS ENVIRONMENT SHOULD BE
FAVORABLE FOR STRENGTHENING, YET NONE OF THE INTENSITY FORECAST GUIDANCE
CALLS FOR SIGNIFICANT STRENGTHENING DURING THIS TIME. GIVEN THE
ENVIRONMENT, THE INTENSITY FORECAST WILL BUCK THE MODEL GUIDANCE AND CALL
FOR SLIGHT STRENGTHENING DURING THE FIRST 24-36 HR. THEREAFTER, THE
LARGE-SCALE MODELS SUGGEST THE POSSIBILITY OF INCREASED VERTICAL WIND SHEAR,
ALTHOUGH THEY DIFFER ON THE DETAILS. THIS, COMBINED WITH COOLING SEA
SURFACE TEMPERATURES, ARE EXPECTED TO CAUSE BERTA TO SLOWLY WEAKEN.
This information is provided as a public service from the
National Hurricane Center
http://www.nhc.noaa.gov
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