Tropical Storm Bertha Forecast Discussion #10

By: National Weather Service
By: National Weather Service

000
WTNT42 KNHC 051452
TCDAT2
TROPICAL STORM BERTHA DISCUSSION NUMBER 10
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL022008
1100 AM EDT SAT JUL 05 2008

WHILE MOVING OVER COOLER WATERS DURING THE PAST 24 HOURS BERTHA
STRUGGLED A LITTLE BIT...HOWEVER NOW THAT IT IS HEADING FOR
SLIGHTLY WARMER WATERS BERTHA APPEARS TO BE A LITTLE BETTER
ORGANIZED. THE CYCLONE HAS MAINTAINED A CLUSTER OF DEEP CONVECTION
JUST NORTH AND WEST OF THE CENTER DURING THE PAST SEVERAL HOURS.
DVORAK INTENSITY ESTIMATES REMAIN BETWEEN 35-45 KT AND THE INITIAL
INTENSITY IS UNCHANGED. CONDITIONS SHOULD BECOME MORE CONDUCIVE
FOR STRENGTHENING AS SSTS ALONG THE PROJECTED PATH GRADUALLY
INCREASE AND THE SHEAR REMAINS LOW DURING THE NEXT 3 DAYS. THE NEW
NHC INTENSITY FORECAST IS UNCHANGED THROUGH 48 HOURS BUT NOW
PREDICTS BERTHA TO REACH HURRICANE STRENGTH IN 72 HOURS.
THEREAFTER...DUE TO UNCERTAINTIES IN THE AMOUNT OF PREDICTED
SHEAR...THE INTENSITY IS HELD A LITTLE BELOW THE LGEM...SHIPS...AND
GFDL MODELS WHICH SHOW ADDITIONAL INTENSIFICATION.

BERTHA HAS BEEN MOVING A LITTLE MORE WESTWARD DURING THE PAST 6-12
HOURS AND THE INITIAL MOTION ESTIMATE IS 280/18. A WEAKNESS IN THE
RIDGE BETWEEN 50W-60W IS FORECAST TO LIFT NORTHWARD AND THE
SUBTROPICAL RIDGE WILL REMAIN THE PREDOMINANT STEERING MECHANISM
FOR THE NEXT SEVERAL DAYS. THIS SHOULD KEEP BERTHA ON A GENERAL
WEST TO WEST-NORTHWEST HEADING AT A RATHER BRISK PACE. THERE
REMAINS A LARGE AMOUNT OF MODEL SPREADS AT DAYS 4 AND 5.
HOWEVER...MOST OF THE MODEL TRACKS HAVE SHIFTED A LITTLE
NORTHWARD...EXCEPT FOR THE UKMET WHICH KEEPS A WEAKER TROPICAL
CYCLONE MOVING WESTWARD. THE MODEL CONSENSUS SHIFTED VERY CLOSE TO
THE NHC TRACK...SO LITTLE CHANGE WAS NEEDED FROM THE PREVIOUS
OFFICIAL FORECAST.

FORECAST POSITIONS AND MAX WINDS

INITIAL 05/1500Z 16.6N 37.3W 45 KT
12HR VT 06/0000Z 17.0N 40.1W 45 KT
24HR VT 06/1200Z 17.6N 43.9W 50 KT
36HR VT 07/0000Z 18.4N 47.6W 55 KT
48HR VT 07/1200Z 19.1N 51.2W 60 KT
72HR VT 08/1200Z 20.8N 57.5W 65 KT
96HR VT 09/1200Z 23.0N 62.5W 65 KT
120HR VT 10/1200Z 25.0N 67.0W 65 KT

$$
FORECASTER BROWN


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