WTPZ45 KNHC 260846 RRA

TCDEP5



HURRICANE IRWIN DISCUSSION NUMBER  16

NWS NATIONAL HURRICANE CENTER MIAMI FL       EP102017

200 AM PDT WED JUL 26 2017



AN EARLIER 0500 UTC METOP-A AMSU IMAGE AND FORTUITOUS ASCAT

A/B OVERPASSES INDICATE THAT IRWIN'S CIRCULATION CENTER IS LOCATED

NEAR THE SOUTHERN EDGE OF THE CLOUD CANOPY.  APPARENTLY, THE

MODERATE SOUTHEASTERLY OUTFLOW PRODUCED BY HURRICANE HILARY IS

AFFECTING IRWIN'S CORE STRUCTURE.  CLOUD TOPS HAVE WARMED DURING

THE PAST SEVERAL HOURS AND A COMPROMISE OF THE DVORAK SUBJECTIVE

T-NUMBERS FROM SAB AND TAFB SUPPORT AN INITIAL INTENSITY OF 70 KT

FOR THIS ADVISORY.  THE GLOBAL MODELS AS WELL AS THE

STATISTICAL-DYNAMICAL INTENSITY GUIDANCE SHOW CONTINUED SLOW

WEAKENING DURING THE NEXT 36 HOURS WHILE THE HURRICANE REMAINS

WITHIN THE IMPINGING UPPER-LEVEL OUTFLOW OF HILARY.  AFTERWARD,

FURTHER GRADUAL WEAKENING IS FORECAST AS THE CYCLONE TRAVERSES

COOLER OCEANIC TEMPERATURES AND ENTERS A LESS THAN FAVORABLE

THERMODYNAMIC ENVIRONMENT.  THE OFFICIAL FORECAST IS SIMILAR TO THE

PREVIOUS PACKAGE AND IS BASED ON THE IVCN CONSENSUS.



THE MUCH ANTICIPATED TURN TOWARD THE WEST-SOUTHWEST HAS FINALLY

COMMENCED, AND THE CYCLONE MOTION IS ESTIMATED TO BE 255/6 KT.

SOME BINARY INTERACTION WITH HILARY DURING THE NEXT 48 HOURS OR

SO SHOULD CAUSE IRWIN TO STALL, AND THEN ACCELERATE CYCLONICALLY

AROUND THE SOUTHEAST THROUGH NORTHEAST PERIPHERY OF HILARY ON DAYS

4 AND 5.  GLOBAL AND ENSEMBLE MODELS, HOWEVER, SHOW A MUCH SLOWER

FORWARD MOTION BEYOND 72 HOURS THAN WHAT WAS INDICATED IN THE

PREVIOUS ADVISORY, AND ADJUSTMENTS TO THE 96 AND 120 HOUR FORECAST

PERIODS HAVE BEEN MADE ACCORDINGLY.  THE NHC FORECAST REFLECTS THIS