Tropical Storm IRENE

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TROPICAL STORM IRENE DISCUSSION NUMBER  34
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 PM EDT FRI AUG 12 2005
 
SINCE THE LAST RECON REPORT AND 00Z SATELLITE INTENSITY ESTIMATES
...IRENE'S CONVECTIVE PATTERN HAS DEGRADED SOMEWHAT. A 12/2245Z SSMI
OVERPASS INDICATED A SHARP DRY SLOT HAD PUSHED INTO THE CIRCULATION
FROM THE NORTH...ALL THE WHILE CLOUD TOPS HAVE WARMED NEAR THE
CENTER AND A CDO FEATURE IS NO LONGER EVIDENT IN INFRARED IMAGERY.
THEREFORE...THE INTENSITY IS BEING MAINTAINED AT 60 KT. HOWEVER...
THE CENTRAL PRESSURE HAS BEEN DECREASED TO 991 MB BASED ON A
12/2300Z PRESSURE OF 995.9 MB REPORTED BY BUOY 41927 LOCATED ABOUT
30 NMI NORTHEAST OF THE CENTER...WHICH WAS LOWER THAN THE LAST
RECON REPORTED CENTRAL PRESSURE OF 997 MB AT 12/2023Z. 
 
THE BEST MOTION ESTIMATE REMAINS 310/09...WHICH IS A LITTLE TO THE
RIGHT OF THE RECON FIX MOTION. A NOAA G-IV JET AIRCRAFT AND AN AIR
FORCE RESERVE AIRCRAFT HAVE BEEN CONDUCTING SYNOPTIC SURVEILLANCE
MISSIONS AROUND IRENE THIS EVENING. DROPSONDE DATA FROM THOSE
AIRCRAFT INDICATE A SLIGHTLY STRONGER AND MORE WESTWARD EXTENSION
OF THE MID-LEVEL RIDGE THAN ANY OF THE MODELS WERE INDICATING FOR
13/00Z...WITH THE UKMET HAVING THE CLOSEST VERIFICATION. THE RIDGE
...ALBEIT SOMEWHAT NARROW...EXTENDS FROM NEAR BERMUDA WESTWARD TO
NORTH CAROLINA. A SHORTWAVE TROUGH HAS MOVED EASTWARD OFF THE U.S.
EAST COAST AND A SHORTWAVE RIDGE OVER THE EASTERN OHIO VALLEY IS
MOVING EASTWARD TO TAKE THE PLACE OF THAT TROUGH. IN THE SHORT TERM
...THIS SHOULD BUILD OR AT LEAST MAINTAIN THE EXISTING RIDGE TO THE
NORTH OF IRENE...WHICH MAY CAUSE A LITTLE MORE WESTWARD MOTION THAN
FORECAST FOR THE NEXT 24 HOURS OR SO. AFTER THAT...ALL THE MODELS
AGREE THAT IRENE WILL ERODE THE RIDGE AND MOVE SLOWLY NORTHWARD
THROUGH THE RIDGE BETWEEN 70-72W LONGITUDE...AND THEN TURN
EAST-NORTHEASTWARD BY 72 HOURS. HOWEVER...GIVEN MORE RIDGE SHOWING
UP IN THE SYNOPTIC DROPSONDE DATA...THERE MAY BE A WESTWARD SHIFT
IN THE 00Z MODEL GUIDANCE. FOR THIS ADVISORY...THOUGH...THE
OFFICIAL TRACK WILL REMAIN CLOSE TO THE PREVIOUS FORECAST TRACK.
 
BRIEF PERIODS OF INTENSIFICATION WILL PROBABLY OCCUR THROUGH AT
LEAST THE NEXT 48 HOURS OR SO...DESPITE WARM SSTS OF AT LEAST 28C
AND FAVORABLE UPPER-LEVEL SHEAR CONDITIONS. THIS IS MAINLY DUE TO
THE VERY DRY AIR THAT IRENE WILL BE MOVING THROUGH AND CONSTANTLY
HAVING TO MIX OUT. THE OFFICIAL INTENSITY FORECAST IS CLOSE TO THE
PREVIOUS ADVISORY AND REMAINS A LITTLE STRONGER THAN THE SHIPS
INTENSITY MODEL...BUT MUCH HIGHER THAN THE GFDL MODEL...WHICH
WEAKENS IRENE TO LESS THAN 30 KT IN 48H.
 
FORECASTER STEWART

FORECAST POSITIONS AND MAX WINDS
 
INITIAL      13/0300Z 29.2N  68.3W    60 KT
 12HR VT     13/1200Z 29.9N  69.3W    65 KT
 24HR VT     14/0000Z 31.4N  70.3W    70 KT
 36HR VT     14/1200Z 33.0N  70.6W    75 KT
 48HR VT     15/0000Z 34.6N  70.5W    75 KT
 72HR VT     16/0000Z 36.7N  70.0W    75 KT
 96HR VT     17/0000Z 38.0N  67.5W    75 KT
120HR VT     18/0000Z 39.0N  61.5W    75 KT

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