000
WTPZ41 KNHC 111444
TCDEP1
 
TROPICAL STORM IRWIN DISCUSSION NUMBER  22
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP112011
800 AM PDT TUE OCT 11 2011
 
SATELLITE IMAGERY INDICATES THAT IRWIN IS MAKING A COMEBACK...AGAIN. 
A CLUSTER OF DEEP CONVECTION HAS RECENTLY FORMED AND INCREASED IN
COVERAGE OVER THE EASTERN SEMICIRCLE...WITH CLOUD TOP TEMPERATURES
LOWER THAN -80C. SATELLITE INTENSITY ESTIMATES HAVE INCREASED DUE
TO THE CONVECTIVE REFORMATION...SO THE INITIAL INTENSITY IS RAISED
TO 35 KT.
 
THE FUTURE FOR IRWIN DOES NOT LOOK BRIGHT. DEEP CONVECTION
ASSOCIATED WITH IRWIN HAS GENERALLY BEEN SUFFERING AS THE CYCLONE
APPARENTLY TAPS RELATIVELY STABLE AIR ASSOCIATED WITH A NEARBY
STRATOCUMULUS FIELD. AS IRWIN PULLS AWAY FROM THIS AREA...IT IS
ASSUMED THAT THE EASTERLY SHEAR WILL BE STRONG ENOUGH TO PREVENT
ANY SIGNIFICANT RE-INTENSIFICATION. AFTER ABOUT 36 HOURS...A FURTHER
INCREASE IN EASTERLY SHEAR IS EXPECTED AS IRWIN ENTERS AN
ENVIRONMENT OF STRENGTHENING LOW-LEVEL WESTERLY FLOW AND EASTERLIES
ALOFT. WEAKENING SHOULD RESULT...AND IRWIN IS SHOWN AS A SHALLOW
REMNANT LOW BY DAY 5...THOUGH IT WOULD NOT BE SURPRISING IF THIS
DEGENERATION OCCURRED SOONER. THE NEW NHC INTENSITY FORECAST IS A
BIT HIGHER THAN THE PREVIOUS FORECAST IN THE SHORT TERM BASED ON
CURRENT TRENDS...AND IT IS SIMILAR TO THE PREVIOUS ONE AT
LATER TIMES. OVERALL...IT IS IN BEST AGREEMENT WITH THE STATISTICAL-
DYNAMICAL AIDS.
 
THE CENTER CONTINUES TO BE HARD TO PIN DOWN...EVEN WITH MICROWAVE
IMAGERY. USING SATELLITE DATA AND SOME EXTRAPOLATION...IT
APPEARS THAT IRWIN IS MOVING 080/06. MODEL GUIDANCE...EXCEPT FOR
THE GFS...SHOWS IRWIN HEADING NORTHEASTWARD DURING THE NEXT 12-60
HOURS AS IT SWINGS AROUND A MID-TROPOSPHERIC LOW CUTTING OFF
SOUTHWEST OF BAJA CALIFORNIA. AFTER THAT...GLOBAL MODELS DEPICT
IRWIN...LIKELY AS A SHALLOW CYCLONE...BEING DRAWN INTO A BROAD
CYCLONIC FLOW NEAR MEXICO AND TURNING GENERALLY SOUTHEASTWARD
AND SLOWING DOWN. THE NEW NHC TRACK FORECAST IS SIMILAR TO BUT NORTH
OF THE PREVIOUS ONE AND ON THE RIGHT SIDE OF THE GUIDANCE ENVELOPE.
 

FORECAST POSITIONS AND MAX WINDS
 
INIT  11/1500Z 15.3N 115.0W   35 KT  40 MPH
 12H  12/0000Z 15.5N 113.7W   35 KT  40 MPH
 24H  12/1200Z 16.1N 111.7W   35 KT  40 MPH
 36H  13/0000Z 17.0N 109.4W   30 KT  35 MPH
 48H  13/1200Z 17.5N 107.7W   30 KT  35 MPH
 72H  14/1200Z 17.6N 105.1W   30 KT  35 MPH
 96H  15/1200Z 16.5N 104.3W   25 KT  30 MPH
120H  16/1200Z 16.0N 104.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
 
$$
FORECASTER KIMBERLAIN