032
WTNT45 KNHC 111447
TCDAT5
TROPICAL STORM ERIN DISCUSSION NUMBER 1
NWS NATIONAL HURRICANE CENTER MIAMI FL AL052025
200 PM CVT MON AUG 11 2025
THE SYSTEM WE HAVE BEEN MONITORING THAT MOVED ACROSS THE CABO VERDE
ISLANDS OVER THE PAST 6-12 H (INVEST 97L) HAS MAINTAINED A SMALL,
BUT PERSISTENT AREA OF DEEP CONVECTION. THIS ACTIVITY PROMPTED AN
EARLIER TAFB SUBJECTIVE DVORAK FIX OF T2.5/35 KT SUGGESTING THE
CONVECTION IS NOW SUFFICENTLY ORGANIZED TO BE CLASSIFIED AS A
TROPICAL CYCLONE. WE ALSO RECEIVED SCATTEROMETER DATA AT 1107 UTC
WITH A PEAK WIND RETRIEVAL OF 39 KT EMBEDDED IN THIS CONVECTION,
WITH AN AMBIGUITY ANALYSIS SUGGESTING THE CIRCULATION IS ALSO
WELL DEFINED, ALBEIT STILL SOMEWHAT ELONGATED ON THE EASTERN EDGE.
THE COMBINATION OF ALL THIS DATA SUGGESTS THAT A TROPICAL STORM HAS
FORMED, AND NHC IS INITIATING ADVISORIES ON TROPICAL STORM ERIN WITH
A CURRENT INTENSITY OF 40 KT.
ERIN IS MOVING QUICKLY OFF TO THE WEST, WITH THE MOTION ESTIMATED AT
275/17 KT. OVER THE NEXT FEW DAYS, THIS MOTION SHOULD CONTINUE WITH
POSSIBLY SOME SLIGHT SOUTH-OF-DUE-WEST MOTION. ERIN'S MOTION IS
PRIMARILY INFLUENCED BY AN EAST-TO-WEST ORIENTED MID-LEVEL RIDGE
DRAPED ACROSS THE SUBTROPICAL ATLANTIC BASIN. BY THE END OF THE
FORECAST PERIOD, THIS RIDGE MAY START TO BECOME MORE ORIENTED TO THE
NORTHEAST OF ERIN, INDUCING A MORE POLEWARD MOTION BY 120 H. THE
INITIAL NHC TRACK FORECAST ELECTS TO STICK FAIRLY CLOSE TO THE HFIP
CORRECTED CONSENSUS APPROACH (HCCA), WHICH IS A TOUCH ON THE SOUTH
SIDE OF THE OVERALL TRACK GUIDANCE ENVELOPE. IT SHOULD BE NOTED THAT
SPREAD IN THE TRACK GUIDANCE, ESPECIALLY THE ENSEMBLES, BEGINS TO
INCREASE MARKEDLY AT THE END OF THE FORECAST PERIOD.
THE INTENSITY FORECAST IN THE SHORT-TERM IS A LITTLE TRICKY. THE
EARLIER SCATTEROMETER DATA INDICATE THE SYSTEM HAS A SMALL
CIRCULATION WHICH COULD BE PRONE TO RAPID INTENSITY CHANGES, EITHER
UP OR DOWN. WHILE VERTICAL WIND SHEAR OVER THE SYSTEM IS FORECAST TO
BE LOW, BETWEEN 5-10 KT OVER THE NEXT 72 HOURS, SEA-SURFACE
TEMPERATURES ARE MORE MARGINAL, AROUND 26-27C, WITH A DECENT AMOUNT
OF DRY MID-LEVEL AIR ALONG THE PATH OF THE TROPICAL STORM. THE FIRST
NHC INTENSITY FORECAST WILL THUS ONLY FORECAST SLOW INTENSIFICATION
IN THE SHORT-TERM, ASSUMING THE MARGINAL SSTS AND LACK OF MID-LEVEL
MOISTURE WILL KEEP THE SMALL VORTEX IN CHECK. AFTER 48 H, HOWEVER,
THE SSTS START TO GRADUALLY INCREASE AND SHOULD ALLOW THE LOCAL
ENVIRONMENT OF ERIN TO MOISTEN UP. THUS, THE RATE OF INTENSIFICATION
WILL LIKELY INCREASE IN THE SECOND HALF OF THE FORECAST PERIOD. THE
NHC INTENSITY FORECAST IS A LITTLE ON THE HIGH SIDE OF THE GUIDANCE
IN THE SHORT-TERM, PARTIALLY DUE TO THE INITIAL INTENSITY, BUT IS IN
LINE WITH THE HCCA INTENSITY AID. BY 120 H, THE HURRICANE-REGIONAL
MODELS (E.G., HWRF/HAFS), AND STATISTICAL-DYNAMICAL AIDS
(EC-SHIPS/LGEM) SHOW ERIN BECOMING A MAJOR HURRICANE, AND THAT WILL
BE EXPLICITLY FORECAST AT THE END OF THE PERIOD.
FORECAST POSITIONS AND MAX WINDS
INIT 11/1500Z 17.4N 28.0W 40 KT 45 MPH
12H 12/0000Z 17.5N 31.2W 45 KT 50 MPH
24H 12/1200Z 17.4N 35.1W 50 KT 60 MPH
36H 13/0000Z 17.1N 38.7W 55 KT 65 MPH
48H 13/1200Z 17.1N 41.7W 60 KT 70 MPH
60H 14/0000Z 17.4N 45.0W 70 KT 80 MPH
72H 14/1200Z 18.0N 48.4W 80 KT 90 MPH
96H 15/1200Z 19.6N 54.0W 90 KT 105 MPH
120H 16/1200Z 21.5N 60.0W 100 KT 115 MPH
FORECASTER PAPIN
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