WTPZ44 KNHC 240847 RRA

TCDEP4



HURRICANE HILARY DISCUSSION NUMBER  12

NWS NATIONAL HURRICANE CENTER MIAMI FL       EP092017

400 AM CDT MON JUL 24 2017



HILARY'S OVERALL CLOUD PATTERN CONTINUES TO BECOME BETTER ORGANIZED,

ALTHOUGH INNER-CORE CONVECTION IS STILL FLUCTUATING SOMEWHAT.

THERE IS WELL-DEFINED UPPER-LEVEL OUTFLOW, PARTICULARLY OVER THE

NORTHWEST AND NORTHEAST QUADRANTS OF THE CIRCULATION.  DVORAK

T-NUMBERS FROM BOTH TAFB AND SAB ARE NOW 4.0, WHICH SUPPORTS

UPGRADING THE SYSTEM TO THE FOURTH HURRICANE OF THE 2017 EASTERN

NORTH PACIFIC SEASON.  HILARY IS EXPECTED TO CONTINUE TRAVERSING

A WARM OCEAN WITH WEAK VERTICAL SHEAR FOR THE NEXT COUPLE OF DAYS,

WHICH FAVORS CONTINUED STRENGTHENING.  RAPID INTENSIFICATION IS A

DISTINCT POSSIBILITY, SINCE THE SHIPS RAPID INTENSIFICATION INDEX

(RII) SHOWS A 60 PERCENT CHANCE OF A 30 KT INCREASE IN INTENSITY

DURING THE NEXT 24 HOURS.  THE NHC FORECAST IS IN LINE WITH THE

RII GUIDANCE, AND IS CLOSE TO THE HFIP CORRECTED CONSENSUS

INTENSITY FORECAST THROUGH 72 HOURS, AND A LITTLE BELOW IT

THEREAFTER WHEN SSTS BENEATH THE CYCLONE ARE EXPECTED TO COOL BELOW

26 DEG C.



A WEST-NORTHWESTWARD MOTION CONTINUES, NEAR 300/7 KT.  THE FLOW ON

THE SOUTHERN PERIPHERY OF A LARGE 500 MB RIDGE THAT EXTENDS WESTWARD

FROM THE SOUTHWESTERN UNITED STATES SHOULD BE THE MAIN STEERING

MECHANISM FOR THE NEXT SEVERAL DAYS.  A SLIGHT STRENGTHENING OF THE

FLOW SHOULD LEAD TO SOME INCREASE IN THE FORWARD SPEED OF HILARY

OVER THE NEXT FEW DAYS.  THERE IS STILL THE POSSIBILITY OF SOME

BINARY INTERACTION WITH TROPICAL STORM IRWIN TO THE WEST, BUT FOR

NOW THIS INTERACTION IS NOT EXPECTED TO BE VERY SIGNIFICANT WITHIN