WTPZ45 KNHC 252043 RRA

TCDEP5



HURRICANE IRWIN DISCUSSION NUMBER  14

NWS NATIONAL HURRICANE CENTER MIAMI FL       EP102017

200 PM PDT TUE JUL 25 2017



IRWIN'S SATELLITE PRESENTATION HAS IMPROVED SINCE THE LAST

ADVISORY, WITH A WELL-DEFINED EYE SHOWING UP IN INFRARED IMAGERY,

AND AN ELONGATED BAND EXTENDING AROUND THE WESTERN AND NORTHERN

SIDE OF THE CIRCULATION.  USING THE EYE PATTERN FROM THE DVORAK

TECHNIQUE YIELDS AN ESTIMATE OF T4.5/77 KT, SO THE INITIAL INTENSITY

IS RAISED TO 75 KT.  IRWIN HAS ALREADY STRENGTHENED BEYOND WHAT WE

WERE ORIGINALLY FORECASTING, SO IT'S A LITTLE DIFFICULT TO KNOW IF

IT WILL INTENSIFY FURTHER.  HOWEVER, 10-15 KT OF SOUTHERLY SHEAR IS

EXPECTED TO REMAIN OVER THE CYCLONE FOR THE NEXT 24 HOURS, AND THE

HURRICANE'S SLOW MOTION COULD CAUSE SOME UPWELLING OF COLDER WATER.

THEREFORE, GRADUAL WEAKENING IS FORECAST DURING THE NEXT 48 HOURS.

AFTER THAT TIME, IRWIN WILL BEGIN INTERACTING WITH HURRICANE

HILARY, AND SINCE IT HAS THE SMALLER CIRCULATION OF THE TWO, IT IS

LIKELY TO SUFFER AND BE THE ONE THAT LOSES INTENSITY.  WATER

TEMPERATURES ALSO COOL SIGNIFICANTLY AS IRWIN ACCELERATES TOWARD

THE NORTH, SO MORE DEFINITIVE WEAKENING IS EXPECTED BY THE END OF

THE FORECAST PERIOD.  SOME OF THE GLOBAL MODELS SHOW IRWIN BECOMING

ABSORBED INTO HILARY'S CIRCULATION BEFORE THE END OF THE FORECAST

PERIOD, SO IT'S POSSIBLE THAT DISSIPATION COULD OCCUR BY DAY 5.



IRWIN CONTINUES TO MOVE GENERALLY WESTWARD, BUT THAT MOTION IS

LIKELY TO BECOME MORE WEST-SOUTHWESTWARD FROM 12-48 HOURS AS HILARY

APPROACHES FROM THE EAST.  THE FUJIWHARA INTERACTION WITH HILARY

WILL THEN CAUSE IRWIN TO STALL AROUND DAY 3, AND THEN ACCELERATE