WTPA43 PHFO 010846

TCDCP3



HURRICANE IGNACIO DISCUSSION NUMBER  30

NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI   EP122015

1100 PM HST MON AUG 31 2015



SHEAR IN EXCESS OF 25 KT IS DEFINITELY TAKING A TOLL ON IGNACIO THIS

EVENING...WITH AN INCREASINGLY ASYMMETRIC CANOPY AND A MORE RAGGED

OVERALL SATELLITE PRESENTATION SINCE THIS AFTERNOON. THE LLCC

POSITION HAS BECOME INCREASINGLY UNCERTAIN WITH THE EYE NO LONGER

DISCERNIBLE IN SATELLITE IMAGERY. THE DISPLACEMENT TO THE NORTHEAST

OF THE UPPER ROTATION...NOTED IN SATELLITE LOOP...FROM AN APPARENT

LLCC NOTED IN 0432 UTC SSMI MICROWAVE IMAGERY STRONGLY HINTS THAT

SHEAR IS FINALLY AFFECTING THE CORE OF THIS SYSTEM. SUBJECTIVE

DVORAK SATELLITE INTENSITY ESTIMATES RANGE FROM 4.0...65 KT...FROM

SAB TO 4.5...77 KT...FROM JTWC AND PHFO. WE WILL ASSIGN 75 KT AS THE

INITIAL INTENSITY FOR THIS ADVISORY...BLENDING CI ESTIMATES FROM THE

SATELLITE CENTERS WITH THE WORSENING SATELLITE PRESENTATION.



ASSUMING THAT THE CORE IS TILTED TOWARD THE NORTHEAST WITH HEIGHT

WITHIN STRONG SOUTHWEST SHEAR...IGNACIO IS MOVING TOWARD THE

NORTHWEST...325 DEGREES...AT 10 KT. THIS IS MORE NORTHERLY THAN THE

PREVIOUS MOTION AND DEVIATES NOTICEABLY TO THE RIGHT OF THE PREVIOUS

FORECAST TRACK. HOWEVER...AN ALTERNATIVE ASSUMPTION OF A STACKED

CORE WOULD HAVE RESULTED IN A MUCH LARGER DEVIATION. TRACK GUIDANCE

REMAINS TIGHTLY PACKED CARRYING IGNACIO GENERALLY TOWARD THE

NORTHWEST THROUGH DAY FIVE...WITH A SLIGHT SWING TO A MORE NORTHERLY

TRACK LATE IN THIS FORECAST PERIOD. THE FORECAST TRACK FOR THIS

ADVISORY WAS BUMPED TO THE RIGHT THROUGH 36 HOURS TO ACCOUNT FOR

INITIAL MOTION...THEN BLENDED BACK INTO THE CONSENSUS GUIDANCE

ENVELOPE AFTERWARDS. THIS TRACK WILL LIKELY BE ALTERED WITH THE NEXT

FEW ADVISORIES AS THE GLOBAL MODELS AND CONSENSUS GRAPPLE WITH HOW

IGNACIO WILL BE STEERED BY THE HIGH TO ITS DISTANT NORTHEAST AND THE

WEAK MID-LEVEL TROUGH TO ITS NORTHWEST.



IN SPITE OF THE HOSTILE SHEAR ENVIRONMENT...IGNACIO IS MOVING OVER

ANOMALOUSLY WARM WATER AND WILL CONTINUE TO DO SO THROUGH AT LEAST

48 HOURS. THIS IS REFLECTED IN INTENSITY GUIDANCE...WHICH IS QUITE

HESITANT TO WEAKEN THIS SYSTEM TOO FAST. OUR FORECAST CALLS FOR

IGNACIO TO VERY GRADUALLY WEAKEN BUT REMAIN AT HURRICANE STRENGTH

THROUGH 36 HOURS. CONTINUED WEAKENING IS THEN EXPECTED THROUGH THE

FORECAST PERIOD AS IGNACIO BEGINS TO FEEL MID-LATITUDE BAROCLINIC

EFFECTS. FOR THIS GUIDANCE PACKAGE...ONLY ECMWF KEEPS THIS SYSTEM AT

HURRICANE STRENGTH THROUGH 120 HOURS. THE FORECAST WEAKENING TREND

MIRRORS THE PREVIOUS ONE AFTER 48 HOURS...KEEPING WHATEVER IS LEFT

OF IGNACIO WITHIN TROPICAL STORM STRENGTH RANGE ON DAY FIVE.



FORECAST POSITIONS AND MAX WINDS



INIT  01/0900Z 23.1N 152.3W   75 KT  85 MPH

 12H  01/1800Z 24.2N 153.4W   70 KT  80 MPH

 24H  02/0600Z 25.4N 154.8W   65 KT  75 MPH

 36H  02/1800Z 26.5N 156.4W   65 KT  75 MPH

 48H  03/0600Z 27.8N 158.2W   60 KT  70 MPH

 72H  04/0600Z 30.6N 161.3W   60 KT  70 MPH

 96H  05/0600Z 34.6N 163.4W   60 KT  70 MPH

120H  06/0600Z 38.8N 164.4W   50 KT  60 MPH



$$

FORECASTER POWELL