WTPA43 PHFO 300905

TCDCP3



HURRICANE IGNACIO DISCUSSION NUMBER  22

NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI   EP122015

1100 PM HST SAT AUG 29 2015



IGNACIO PRESENTS A WELL-DEFINED 20 NM WIDE EYE WITH A DEEP

CONVECTIVE CANOPY WHICH HAS BEEN STEADILY SHRINKING SINCE 0600 UTC.

ALL THREE SATELLITE CENTERS DERIVED SUBJECTIVE DVORAK SATELLITE

INTENSITY ESTIMATES OF 6.0...115 KT...AT 0600 UTC. UW-CIMSS ADT WAS

HIGHER AT 6.3 OR 122 KT. HOWEVER...WEATHER RECONNAISSANCE AIRCRAFT

SFMR FOUND 126 KT WITHIN THE NORTHEAST EYEWALL DURING THE SECOND OF

THREE...YES THREE...CENTER FLYTHROUGHS. SPLASH WIND CORRECTED

CENTRAL PRESSURE WAS FOUND TO BE 942 MB...LOWER THAN EXPECTED...ON

THE FIRST PASS BUT 945 MB ON THE THIRD PASS. BOTH PRESSURE ESTIMATES

WERE LOWER THAN IN THE PREVIOUS ADVISORY. IGNACIO LIKELY REACHED A

PEAK INTENSITY OF 125 KT AS THE AIRCRAFT WAS SAMPLING ITS

STRUCTURE...AND THIS WILL BE THE INITIAL INTENSITY FOR THIS

ADVISORY.



FORECAST PHILOSOPHY HAS CHANGED LITTLE SINCE THE LAST ADVISORY.

IGNACIO CONTINUES TO TRACK NORTHWEST...315 DEGREES AT 7 KT OVER THE

PAST 12 HOURS...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 ONLY CHALLENGE IS THAT...IN THE

SHORTER RANGE...THREE TO SIX HOURS...THERE ARE HINTS OF A MORE

NORTHERLY MOTION. LIKE THE LAST FEW RUNS...TRACK GUIDANCE THIS TIME

REMAINS TIGHTLY PACKED...TAKING THIS HURRICANE ALMOST IN A STRAIGHT

LINE NORTHWESTWARD THROUGH THE FIVE-DAY FORECAST PERIOD. HWRF AND

GFDL SHIFTED A BIT TO THE RIGHT...AS DID MOST CONSENSUS BLENDS.

HOWEVER...THE GFS SHIFTED SLIGHTLY LEFT. WE HAVE CONSISTENTLY KEPT

THE FORECAST TRACK ALONG THE LEFT EDGE OF THE GUIDANCE ENVELOPE AND

WE WILL DO SO THIS TIME AS WELL. THAT SAID...THE FORECAST TRACK WAS

SHIFTED SLIGHTLY TO THE RIGHT TO ACCOUNT FOR THE SHORT TERM MOTION

BEING A BIT MORE NORTHERLY THAN 12 HOUR MOTION. THIS CHANGE IS

ACTUALLY QUITE CONSERVATIVE...KEEPING THE TRACK LEFT OF CONSENSUS

AND CLOSELY ALIGNED WITH GFS. A 1 OR 2 KT DECREASE IN FORWARD MOTION

WAS ALSO INTRODUCED THROUGH 36 HOURS...NOT ENOUGH TO CHANGE THE

STATUS OF TROPICAL STORM WATCHES ACROSS THE HAWAIIAN ISLANDS.



SATELLITE LOOP SHOWS SHEAR IS BEGINNING TO TAKE ITS TOLL ON THIS

SYSTEM...IN SPITE OF THE INTENSITY MAX LIKELY REACHED A FEW HOURS

AGO. OUTFLOW APPEARS TO BE HINDERED TO THE NORTHWEST AND THE EROSION

ALONG THE WESTERN FLANK OF THE DEEP CONVECTIVE CANOPY SEEMS TO

CONFIRM THE PRESENCE OF INCREASING WESTERLY SHEAR. SHIPS INTENSITY

GUIDANCE DEPICTS STEADILY INCREASING SHEAR THROUGH 96 HOURS AND THE

FORECAST CALLS FOR IGNACIO TO FOLLOW A WEAKENING TREND SIMILAR TO

THAT OF THE LAST ADVISORY. WE KEEP THIS SYSTEM STRONGER THAN SHIPS

DEPICTS THROUGH DAY FIVE BUT WEAKER THAN DEPICTED IN DYNAMIC

MODELS.



IGNACIO WILL PASS CLOSE ENOUGH TO THE MAIN HAWAIIAN ISLANDS TO

JUSTIFY KEEPING A TROPICAL STORM WATCH IN EFFECT FOR THE BIG ISLAND

AND THE ISLANDS OF MAUI COUNTY.



FORECAST POSITIONS AND MAX WINDS



INIT  30/0900Z 17.4N 147.9W  125 KT 145 MPH

 12H  30/1800Z 18.2N 148.9W  115 KT 135 MPH

 24H  31/0600Z 19.2N 150.2W  110 KT 125 MPH

 36H  31/1800Z 20.3N 151.6W   95 KT 110 MPH

 48H  01/0600Z 21.3N 152.9W   80 KT  90 MPH

 72H  02/0600Z 23.4N 155.8W   75 KT  85 MPH

 96H  03/0600Z 25.6N 159.2W   65 KT  75 MPH

120H  04/0600Z 27.8N 162.3W   60 KT  70 MPH



$$

FORECASTER POWELL