WTPZ45 KNHC 291434 RRA

TCDEP5



TROPICAL STORM IRWIN DISCUSSION NUMBER  29

NWS NATIONAL HURRICANE CENTER MIAMI FL       EP102017

800 AM PDT SAT JUL 29 2017



IRWIN'S CLOUD PATTERN HAS NOT CHANGED MUCH SINCE YESTERDAY. IT

CONSISTS OF A LOW-LEVEL CENTER JUST TO THE NORTH OF A CYCLONICALLY

CURVED CONVECTIVE BAND IN THE SOUTHERN SEMICIRCLE. AN AVERAGE

OF THE DVORAK INTENSITY ESTIMATES SUPPORTS A 50-KT TROPICAL CYCLONE.

THE CIRCULATION IS STILL OVER WARM WATERS AND IRWIN COULD MAINTAIN

THE SAME INTENSITY FOR ANOTHER 12 HOURS OR SO. AFTER THAT TIME, THE

CYCLONE WILL BEGIN TO MOVE OVER COOLER WATERS RESULTING IN GRADUAL

WEAKENING. MODELS STILL DISAGREE IF HILARY AND IRWIN WILL MERGE AS

FORECAST BY THE GFS, OR IF BOTH SYSTEMS WILL DISSIPATE NEARBY OVER

COOL WATERS AS SUGGESTED BY THE ECMWF. THE NHC FORECAST OPTS FOR THE

ECMWF PROPOSAL, BUT REGARDLESS OF THE SOLUTION, BOTH SYSTEM ARE

ANTICIPATED TO BE WEAK REMNANT LOWS OR MAY HAVE EVEN DISSIPATED BY

THEN.



TODAY, I FOUND IRWIN BASICALLY IN THE SAME SPOT I LEFT IT YESTERDAY.

IT WAS ANTICIPATED THAT THE CYCLONE WAS GOING TO BE MEANDERING

FOR A WHILE WITHIN VERY WEAK STEERING CURRENTS, BUT IT APPEARS

THAT THIS IS ABOUT TO CHANGE SOON. IRWIN WILL BE INFLUENCED BY THE

SOUTHERLY FLOW IN THE WAKE OF HILARY, AND THE CYCLONE SHOULD BEGIN

TO MOVE NORTHWARD AND NORTHWESTWARD WITH AN INCREASE IN FORWARD

SPEED DURING THE NEXT 12 HOURS AND BEYOND. THE TRACK FORECAST IS

SIMILAR TO THE PREVIOUS ONE, AND IS BASICALLY ON TOP OF THE

MULTI-MODEL CONSENSUS TVCX AND TVCN WHICH HAVE BEEN THE MODELS WITH

THE HIGHEST SKILL IN FORECASTING IRWIN SO FAR.





FORECAST POSITIONS AND MAX WINDS



INIT  29/1500Z 15.1N 124.9W   50 KT  60 MPH