WTPA43 PHFO 300302

TCDCP3



HURRICANE IGNACIO DISCUSSION NUMBER  21

NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI   EP122015

500 PM HST SAT AUG 29 2015



IGNACIO CONTINUES TO HAVE A WELL DEFINED...20 NM WIDE EYE SURROUNDED

BY A RING OF COLD CONVECTIVE CLOUDS. DVORAK INTENSITY ESTIMATES

WERE A UNANIMOUS 6.0 FROM THE SATELLITE AGENCIES...AND THE UW-CIMSS

ADT INTENSITY ESTIMATE WAS 6.4. BASED ON A BLEND OF THESE DATA...

WILL MAINTAIN THE 120 KT /CATEGORY 4 ON THE SAFFIR-SIMPSON SCALE/

INTENSITY. THE NEXT RECONNAISSANCE MISSION IS SCHEDULED TO

INVESTIGATE IGNACIO AT 0600 UTC. NOTE THAT HURRICANES IGNACIO AND

KILO ARE BOTH CATEGORY 4 AS OF THIS ADVISORY CYCLE...A VERY RARE

OCCURRENCE INDEED FOR THE CENTRAL PACIFIC BASIN.



THE HURRICANE IS MOVING STEADILY TOWARD THE NORTHWEST...315 DEGREES

AT 8 KT...THROUGH A WEAKNESS IN THE MID-LEVEL RIDGE EAST OF HAWAII

AND TOWARD A WEAK TROUGH LOCATED TO THE NORTH OF THE NORTHWESTERN

HAWAIIAN ISLANDS. THE TRACK GUIDANCE IS IN GOOD AGREEMENT THAT THIS

GENERAL MOTION WILL CONTINUE FOR THE NEXT FEW DAYS. OUR FORECAST

TRACK IS VERY CLOSE TO THE PREVIOUS FORECAST AS WELL AS THE

CONSENSUS GUIDANCE FOR THE NEXT 24 HOURS. BEYOND 24 HOURS OUR TRACK

BENDS MORE TO THE LEFT WITH TIME IN ANTICIPATION THAT IGNACIO WILL

WEAKEN A BIT FASTER THAN THE DYNAMICAL MODELS INDICATE.



THE UW-CIMSS WIND SHEAR ANALYSIS AND CONVENTIONAL SATELLITE IMAGERY

SHOWS THAT SOUTHWESTERLY WIND SHEAR IS BEGINNING TO AFFECT IGNACIO.

HIGH CLOUDS FROM THE HURRICANE ARE STARTING TO GET PULLED TO THE

NORTHEAST. ACCORDING TO THE ANALYSIS...THE SHEAR IS NEAR 10 KT...

BUT INCREASES TO 15-20 KT TO THE NORTHWEST OF THE CYCLONE...AND

WILL INCREASE FURTHER AND BECOME QUITE STRONG AS IGNACIO APPROACHES

HAWAII. THIS WILL LEAD TO A STEADY WEAKENING TREND...DESPITE SEA

SURFACE TEMPERATURES OF 27-28C ALONG MOST OF THE FORECAST TRACK.

THE WEAKENING WILL BE GRADUAL OVER THE NEXT 24 HOURS...THEN MORE

RAPID ONCE THE SHEAR BEGINS TO IMPACT THE CORE OF THE HURRICANE.

OUR WEAKENING TREND IS NOT AS FAST AS THE SHIPS...BUT FASTER THAN

THE DYNAMIC MODELS AND IN GOOD AGREEMENT WITH THE INTENSITY

CONSENSUS.



THE RELATIVELY CLOSE PROXIMITY TO THE EXPECTED OUTER EXTENT OF THE

34 KNOT WIND RADII IN THE SOUTHWEST QUADRANT REQUIRES MAINTAINING

THE TROPICAL STORM WATCH FOR THE BIG ISLAND...AND THE ISSUANCE OF

A TROPICAL STORM WATCH FOR MAUI COUNTY AT THIS TIME.





FORECAST POSITIONS AND MAX WINDS



INIT  30/0300Z 17.0N 147.6W  120 KT 140 MPH

 12H  30/1200Z 17.9N 148.7W  115 KT 135 MPH

 24H  31/0000Z 19.0N 150.0W  110 KT 125 MPH

 36H  31/1200Z 20.0N 151.5W   95 KT 110 MPH

 48H  01/0000Z 21.0N 153.0W   80 KT  90 MPH

 72H  02/0000Z 23.0N 156.0W   70 KT  80 MPH

 96H  03/0000Z 25.0N 159.0W   60 KT  70 MPH

120H  04/0000Z 27.0N 162.0W   55 KT  65 MPH



$$

FORECASTER R BALLARD