[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT44 KNHC 121441
TCDAT4
TROPICAL STORM IRENE DISCUSSION NUMBER  32
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 AM EDT FRI AUG 12 2005

THE CLOUD PATTERN HAS DEFINITELY BECOME BETTER ORGANIZED SINCE
YESTERDAY. THERE IS A LOW-LEVEL CENTER EMBEDDED WITHIN THE DEEP
CONVECTION AND A WELL-DEFINED UPPER-LEVEL OUTFLOW. MICROWAVE DATA
SHOW A CONVECTIVE RING ASSOCIATED WITH THE CENTER OF IRENE.
T-NUMBERS FROM ALL AGENCIES HAVE REACHED 3.5 ON THE DVORAK SCALE SO
THE INITIAL INTENSITY HAS BEEN INCREASED TO 55 KNOTS. HOWEVER...A
MORE ACCURATE MEASUREMENT OF THE INTENSITY AND STRUCTURE OF IRENE
WILL BE KNOWN WHEN AN AIR FORCE PLANE REACHES THE CYCLONE LATER
TODAY. THIS IS THE FIRST FLIGHT INTO IRENE. THE SHEAR AHEAD OF
IRENE IS FORECAST TO BE LOW..AND THAT SHOULD LEAD TO ADDITIONAL
STRENGTHENING. HOWEVER...THE CYCLONE WILL MOVE OVER A POCKET OF
RELATIVELY COOL WATERS LEFT BY FRANKLIN AND HARVEY. SO
INTENSIFICATION BEYOND CATEGORY ONE HURRICANE STRENGTH IS NOT
ANTICIPATED. THIS IS CONSISTENT WITH THE SHIPS AND THE GFDL MODELS.

IRENE IS MOVING TOWARD THE NORTHWEST OR 305 DEGREES AT 11 KNOTS
AROUND A STRONG MID-LEVEL SUBTROPICAL RIDGE. AS THE RIDGE MOVES
EASTWARD...IRENE SHOULD TURN MORE TOWARD THE NORTH-NORTHWEST AND
NORTH INTO AN AREA OF LIGHT STEERING CURRENTS. THIS WOULD RESULT IN
A SIGNIFICANT DECREASE IN FORWARD SPEED BEYOND 3 DAYS AND IN
FACT...IRENE COULD BEGIN MEANDERING. THIS IS CONSISTENT WITH MANY
OF THE GLOBAL MODELS WHICH SHOW BASICALLY VERY WEAK STEERING FLOW
NEAR THE 3 TO 5 DAY FORECAST POSITION OF IRENE. EVENTUALLY...A
WESTERLY STEERING FLOW SHOULD BECOME ESTABLISHED WHICH SHOULD TURN
THE CYCLONE AWAY FROM THE US COAST. THAT IS STILL TOO FAR IN THE
FUTURE TO BE CERTAIN.

FORECASTER AVILA


FORECAST POSITIONS AND MAX WINDS

INITIAL      12/1500Z 28.3N  66.8W    55 KT
 12HR VT     13/0000Z 29.2N  68.1W    65 KT
 24HR VT     13/1200Z 30.0N  69.3W    75 KT
 36HR VT     14/0000Z 31.0N  70.0W    75 KT
 48HR VT     14/1200Z 32.0N  71.0W    75 KT
 72HR VT     15/1200Z 34.0N  72.0W    75 KT
 96HR VT     16/1200Z 35.0N  72.0W    75 KT
120HR VT     17/1200Z 36.5N  71.5W    75 KT


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