WTPA43 PHFO 290857 TCDCP3 HURRICANE IGNACIO DISCUSSION NUMBER 18 NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI EP122015 1100 PM HST FRI AUG 28 2015 DATA COLLECTED BY A U.S. AIR FORCE RESERVE RECONNAISSANCE AIRCRAFT WERE UTILIZED IN THE INITIAL INTENSITY ESTIMATE...CENTRAL PRESSURE...CENTER POSITION AND WIND RADII FOR THIS PACKAGE. THE AIRCRAFT DATA CONFIRMED THAT THE ONGOING SUBJECTIVE AND OBJECTIVE SATELLITE-DERIVED INTENSITY ESTIMATES WERE REASONABLY ACCURATE... AS MAX FLIGHT LEVEL WINDS NEAR 84 KT AND MAX SFMR WINDS NEAR 77 KT SUPPORT MAINTAINING THE INITIAL INTENSITY AT 80 KT FOR THIS ADVISORY. A WARM SPOT IN INFRARED SATELLITE IMAGERY HAS AIDED IN SUBSEQUENT CENTER FIXING AFTER THE AIRCRAFT LEFT THE HURRICANE AROUND 0530Z. ANOTHER RECONNAISSANCE FLIGHT BY THE HURRICANE HUNTERS IS SCHEDULED IN TIME FOR THE 1800Z ADVISORY CYCLE SATURDAY MORNING. THE INITIAL MOTION ESTIMATE FOR THIS ADVISORY IS 300/08 KT...WITH THE CLOUD-FILLED EYE WOBBLING AROUND ON A TRAJECTORY THAT LIES VERY CLOSE TO THE PREVIOUS FORECAST TRACK. THE TRACK FORECAST PHILOSOPHY HAS CHANGED LITTLE...WITH IGNACIO FORECAST TO TRACK NORTHWEST TOWARD A BREAK IN A MID-LEVEL RIDGE THAT IS CENTERED TO THE DISTANT NORTHEAST. THE TRACK GUIDANCE IS ONCE AGAIN TIGHTLY CLUSTERED AND OFFERS LITTLE IN THE WAY OF SIGNIFICANT CHANGE...WITH THE OFFICIAL TRACK FORECAST STILL RIDING THE LEFT HAND SIDE OF THE GUIDANCE ENVELOPE...ALTHOUGH THE DAY 5 GFS FORECAST POSITION WAS RIGHT ON TOP OF THE PREVIOUS OFFICIAL FORECAST. THEREFORE...THE UPDATED FORECAST REPRESENTS VERY LITTLE CHANGE. WATER VAPOR IMAGERY...AS WELL AS UPPER-AIR AND UW-CIMSS ANALYSES... INDICATE THAT IGNACIO IS IN AN AREA OF WEAK SHEAR...IN A COL BETWEEN RIDGES ALOFT CENTERED TO THE EAST-NORTHEAST...AND TO THE WEST. LATEST INFRARED IMAGES DEPICT A WELL-DEFINED OUTFLOW CHANNEL TO THE NORTH OF THE HURRICANE. IN THE SHORT-TERM...SUFFICIENTLY WARM WATER TEMPERATURES AND LIGHT SHEAR LIE ALONG THE FORECAST TRACK...AND THE OFFICIAL FORECAST CLOSELY FOLLOWS TRENDS PRESENTED BY THE INTENSITY CONSENSUS IVCN...AND SHIPS GUIDANCE...IN ANTICIPATING STRENGTHENING. AFTER 36 TO 48 HOURS...SOUTHWESTERLY SHEAR IS FORECAST TO GRADUALLY INCREASE WITH ONLY SMALL CHANGES IN UNDERLYING WATER TEMPERATURES AND OCEAN HEAT CONTENT. THEREFORE...A GRADUAL WEAKENING TREND FORECAST TO COMMENCE ON SUNDAY IS EXPECTED TO PERSIST THROUGH DAY 5. DATA FROM THE AIRCRAFT WERE USED TO INCREASE THE INITIAL WIND RADII...WITH THE LARGEST CHANGES BEING AN EXPANSION OF THE RADII IN THE SOUTHWEST QUADRANT. FORECAST POSITIONS AND MAX WINDS INIT 29/0900Z 15.7N 146.0W 80 KT 90 MPH 12H 29/1800Z 16.3N 147.0W 85 KT 100 MPH 24H 30/0600Z 17.3N 148.4W 90 KT 105 MPH 36H 30/1800Z 18.2N 149.8W 90 KT 105 MPH 48H 31/0600Z 19.1N 151.1W 85 KT 100 MPH 72H 01/0600Z 21.2N 153.8W 75 KT 85 MPH 96H 02/0600Z 23.5N 156.5W 65 KT 75 MPH 120H 03/0600Z 25.5N 159.0W 60 KT 70 MPH $$ FORECASTER BIRCHARD