[Tropical] Tropical Cyclone Discussion

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WTNT45 KNHC 160245
TCDAT5

TROPICAL STORM ERIN DISCUSSION NUMBER   5
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL052013
1100 PM AST THU AUG 15 2013

CONVECTION ASSOCIATED WITH ERIN HAS BEEN ON THE WANE DURING MOST OF
THE EVENING HOURS...ALTHOUGH RECENTLY A SMALL BURST HAS FORMED EAST
OF THE CENTER.  MICROWAVE PASSES SUGGEST THE SYSTEM IS NOT WELL
ORGANIZED...WITH THE LOW-LEVEL CENTER APPARENTLY WEST OF THE MID-
LEVEL CENTER.  THE INITIAL INTENSITY IS BEING HELD AT 35 KT IN
AGREEMENT WITH THE DVORAK ESTIMATE FROM TAFB.  THE OVERALL
ENVIRONMENT FOR THE NEXT DAY OR TWO SEEMS TO BE CONDUCIVE FOR SOME
STRENGTHENING WITH THE SHEAR FORECAST TO BE LIGHT BUT A LIMITING
FACTOR OF MARGINAL SSTS. IN A FEW DAYS...ALTHOUGH SSTS ARE FORECAST
TO INCREASE...THE GLOBAL MODELS SHOW AN INCREASE IN SHEAR...WHICH
WOULD FACILITATE RATHER DRY AIR ALOFT ENTRAINING INTO THE CENTRAL
CORE OF ERIN.  THUS...THE OFFICIAL NHC FORECAST SHOWS WEAKENING
AFTER DAY 3...WHICH IS CONSISTENT WITH THE PREVIOUS FORECAST AND
THE FLORIDA STATE SUPERENSEMBLE.

MICROWAVE FIXES GIVE AN INITIAL MOTION OF 295/13. THIS GENERAL
COURSE IS EXPECTED FOR THE NEXT COUPLE OF DAYS WHILE A MID-LEVEL
RIDGE REMAINS TO THE NORTHEAST OF THE TROPICAL CYCLONE. AFTER THAT
TIME...THE BIGGEST UNCERTAINTY IS WHETHER A WEAKNESS IN THE RIDGE
FROM A MID- TO UPPER-LEVEL LOW LOCATED OVER THE EASTERN ATLANTIC
WILL ALLOW THAT TRACK TO CONTINUE.  IF THE STORM IS SHALLOW
ENOUGH...IT WILL PROBABLY MISS THE WEAKNESS AND INSTEAD TAKE A MORE
WESTWARD TURN BECAUSE OF A STRONGER LOW-LEVEL RIDGE. ALTHOUGH THE
NEW NHC FORECAST IS SHIFTED NORTHWARD TO COME INTO BETTER AGREEMENT
WITH THE SOUTHERN SIDE OF THE GUIDANCE ENVELOPE...IT IS STILL WELL
TO THE SOUTH OF THE DYNAMICAL MODEL CONSENSUS. FURTHER ADJUSTMENTS
COULD STILL BE NECESSARY IF THIS NORTHWARD TREND IN THE GUIDANCE
PERSISTS IN FUTURE CYCLES.


FORECAST POSITIONS AND MAX WINDS

INIT  16/0300Z 15.5N  29.1W   35 KT  40 MPH
 12H  16/1200Z 16.3N  31.1W   35 KT  40 MPH
 24H  17/0000Z 17.5N  33.4W   40 KT  45 MPH
 36H  17/1200Z 18.6N  35.5W   45 KT  50 MPH
 48H  18/0000Z 19.6N  37.4W   45 KT  50 MPH
 72H  19/0000Z 20.5N  41.5W   45 KT  50 MPH
 96H  20/0000Z 21.5N  46.0W   35 KT  40 MPH
120H  21/0000Z 22.5N  50.0W   30 KT  35 MPH

$$
FORECASTER BLAKE


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