Hurricane IGOR

ZCZC MIATCDAT1 ALL
TTAA00 KNHC DDHHMM
HURRICANE IGOR DISCUSSION NUMBER  31
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112010
500 PM AST WED SEP 15 2010
 
INFRARED SATELLITE PICTURES INDICATE THAT IGOR IS MAINTAINING ITS
CONVECTIVE ORGANIZATION...WITH INNER CORE CONVECTION MORE VIGOROUS
THAN EARLIER. HOWEVER...VISIBLE SATELLITE IMAGES SUGGEST THAT THE
EYEWALL REPLACEMENT CYCLE IGOR IS EXPERIENCING IS STILL OCCURRING.
A DISTINCT BUT PARTIAL INNER EYEWALL IS EVIDENT AND AN OUTER
EYEWALL NOW AT 30-40 NM RADIUS SEEMS TO BE GRADUALLY CONTRACTING.
SUBJECTIVE DVORAK CLASSIFICATIONS ARE AT 5.5 AND 6.0 FROM SAB AND
TAFB...RESPECTIVELY...WHILE THE LATEST 3-HOURLY AVERAGED ADT VALUE
IS CLOSE TO 6.0. THESE ESTIMATES ARE THE BASIS FOR KEEPING THE
INITIAL INTENSITY AT 115 KT FOR THIS ADVISORY. THERE ARE NO OBVIOUS
LARGE-SCALE FACTORS THAT COULD CAUSE A SIGNIFICANT WEAKENING OF
IGOR DURING THE NEXT 2-3 DAYS. ANY CHANGES IN INTENSITY DURING THIS
TIME ARE MOST LIKELY TO BE RELATED TO INNER CORE DYNAMICS FOR WHICH
PREDICTABILITY IS LOW. IN 3-4 DAYS...GLOBAL DYNAMICAL MODELS
CONTINUE TO SHOW AN INCREASE IN SOUTHERLY SHEAR...AND IGOR SHOULD
REACH MARGINAL SEA SURFACE TEMPERATURES TOWARD THE END OF THE
PERIOD. THE STATISTICAL-DYNAMICAL GUIDANCE RESPONDS TO THESE
FACTORS BY SHOWING A GRADUAL WEAKENING BEYOND 72 HOURS. THE
OFFICIAL NHC INTENSITY IS BASICALLY UNCHANGED...WITH THE FORECAST
STILL INDICATING SOME POTENTIAL FOR RE-INTENSIFICATION IN THE SHORT
TERM AFTER THE CURRENT EYEWALL REPLACEMENT CYCLE ENDS.
 
THERE HAS BEEN LITTLE CHANGE TO THE MOTION...AND THE LATEST ESTIMATE
IS 295/07. IGOR IS MOVING AROUND THE SOUTHWEST PERIPHERY OF THE
SUBTROPICAL RIDGE OVER THE EASTERN ATLANTIC AND IS GRADUALLY
ENTERING A PRONOUNCED WEAKNESS IN THE WESTERN ATLANTIC. THIS
SYNOPTIC PATTERN SHOULD STEER IGOR ON A NORTHWESTWARD AND THEN
NORTH-NORTHWESTWARD COURSE DURING THE NEXT 2-3 DAYS. DURING THIS
TIME...SEVERAL SHORTWAVE TROUGHS MOVING THROUGH THE WEAKNESS IN THE
WESTERN ATLANTIC SHOULD HAVE LITTLE EFFECT ON IGOR. HOWEVER...
DYNAMICAL MODELS ARE IN GENERALLY GOOD AGREEMENT THAT A VIGOROUS
SHORTWAVE TROUGH MOVING THROUGH THE NORTHEASTERN STATES/CANADIAN
MARITIMES IN ABOUT 4-5 DAYS SHOULD BEGIN TO INDUCE RECURVATURE. THE
GFS/HWRF/GFDL HAVE BEEN INDICATING A MORE ROBUST SHORTWAVE FEATURE
AND A SHARPER RECURVATURE DURING THE PAST SEVERAL RUNS. ON THE
OTHER HAND...THE UKMET...ECMWF...AND THE ECMWF ENSEMBLE MEAN HAVE
HAD A WEAKER AND MORE PROGRESSIVE SHORTWAVE THAT COULD DELAY
RECURVATURE AND ALLOW FOR A MORE WESTWARD TRACK. THE OFFICIAL NHC
TRACK FORECAST REMAINS ABOUT THE SAME AS BEFORE AND IS VERY NEAR THE
MULTI-MODEL CONSENSUS...CONTINUING TO SHOW IGOR PASSING CLOSE TO
BERMUDA IN ABOUT 4 DAYS.
 
 
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      15/2100Z 20.1N  55.6W   115 KT
 12HR VT     16/0600Z 20.6N  56.7W   110 KT
 24HR VT     16/1800Z 21.4N  58.2W   115 KT
 36HR VT     17/0600Z 22.4N  59.8W   120 KT
 48HR VT     17/1800Z 23.5N  61.5W   120 KT
 72HR VT     18/1800Z 26.5N  64.0W   105 KT
 96HR VT     19/1800Z 31.0N  65.0W    95 KT
120HR VT     20/1800Z 36.0N  61.5W    80 KT
 
$$
FORECASTER KIMBERLAIN
 
NNNN