398
WTPA43 PHFO 020853
TCDCP3
TROPICAL STORM IGNACIO DISCUSSION NUMBER 34
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI EP122015
1100 PM HST TUE SEP 01 2015
DEEP CONVECTION HAS REMAINED CONFINED MAINLY TO THE NORTH AND WEST
OF THE LOW LEVEL CIRCULATION CENTER /LLCC/ DURING THE EVENING...WITH
JUST LAYERED CLOUDS AND LITTLE DEEP CONVECTION SOUTH OF THE LLCC.
WHILE AN INTERMITTENT WARM SPOT NEAR THE LLCC HAS BEEN EVIDENT IN
RECENT INFRARED SATELLITE IMAGERY...SUBJECTIVE DVORAK CURRENT
INTENSITY ESTIMATES CAME IN AT 3.5/55KT FROM ALL THREE AGENCIES...
AND THE INITIAL INTENSITY WILL BE HELD AT 60 KT FOR THIS ADVISORY.
A SERIES OF MICROWAVE IMAGES AND THE 0600Z SUBJECTIVE CENTER
POSITION ESTIMATES SUGGEST THAT IGNACIO SLOWED DOWN SLIGHTLY DURING
THE LATE AFTERNOON AND EARLY EVENING...AND THE INITIAL MOTION
ESTIMATE IS 310/09 KT. IGNACIO IS FORECAST TO CONTINUE MOVING
STEADILY TO THE NORTHWEST DURING THE NEXT 36 TO 48 HOURS...TOWARD A
WEAKNESS IN THE SUBTROPICAL RIDGE TO THE NORTH OF FRENCH FRIGATE
SHOALS. THERE IS NO SIGNIFICANT CHANGE TO THIS PORTION OF THE
FORECAST TRACK...WHICH LIES VERY CLOSE TO THE PREVIOUS TRACK AND THE
TVCN CONSENSUS. BEYOND 48 HOURS...IGNACIO SHOULD ACCELERATE
NORTHWARD AS IT BECOMES EMBEDDED IN DEEP SOUTHERLY FLOW TO THE EAST
OF A LONGWAVE TROUGH. THE RELIABLE TRACK GUIDANCE REMAINS IN GOOD
AGREEMENT DURING THIS TIME...AND THE LATEST ECMWF SHIFTED EASTWARD
INTO MUCH BETTER AGREEMENT WITH THE GFS/TVCN AT DAYS 4 AND 5. THE
NEW FORECAST TRACK HAS BEEN SHIFTED SOMEWHAT TO THE RIGHT OF THE
PREVIOUS TRACK FOR THOSE FORECAST TIMES...BUT STILL LIES ALONG THE
LEFT EDGE OF THE GUIDANCE ENVELOPE AND IS IN CLOSEST AGREEMENT WITH
THE ECMWF.
IGNACIO CONTINUES TO FEEL THE EFFECTS OF MODERATE SOUTHWESTERLY
VERTICAL WIND SHEAR...WITH THE LATEST UW-CIMSS AND SHIPS ANALYSES
INDICATING SHEAR MAGNITUDE NEAR 20 KT. THE CYCLONE MAY HAVE A WINDOW
OF SOMEWHAT LESS HOSTILE CONDITIONS DURING THE NEXT 24 TO 36
HOURS...WHEN SHEAR MAY LESSEN SOMEWHAT AND THE FORECAST TRACK
WILL REMAIN OVER SEA SURFACE TEMPERATURES NEAR 27C. THE NEW
INTENSITY FORECAST WILL MAINTAIN IGNACIO AT 60 KT DURING THIS
TIME...IN REASONABLE AGREEMENT WITH THE LGEM AND ICON CONSENSUS...
BUT BELOW THE SHIPS WHICH BRINGS IGNACIO BACK TO MINIMAL HURRICANE
INTENSITY IN 24 HOURS. A SLOW WEAKENING TREND SHOULD COMMENCE BY 48
HOURS...WHEN IGNACIO WILL BE MOVING NORTHWARD OVER COOLER WATERS.
IGNACIO MAY BEGIN TO UNDERGO EXTRATROPICAL TRANSITION BY THE END OF
THE FORECAST PERIOD AS IT MOVES NORTH OF 40N AND ACROSS INCREASINGLY
COLD WATERS OF THE NORTH PACIFIC. WILL MAINTAIN IGNACIO AS A
TROPICAL SYSTEM THROUGH 120 HOURS FOR THIS FORECAST CYCLE...IN
COORDINATION WITH THE OCEAN PREDICTION CENTER IN WASHINGTON DC.
FORECAST POSITIONS AND MAX WINDS
INIT 02/0900Z 25.2N 156.2W 60 KT 70 MPH
12H 02/1800Z 25.9N 157.4W 60 KT 70 MPH
24H 03/0600Z 27.2N 159.6W 60 KT 70 MPH
36H 03/1800Z 28.4N 161.6W 60 KT 70 MPH
48H 04/0600Z 29.7N 163.0W 55 KT 65 MPH
72H 05/0600Z 33.6N 164.2W 50 KT 60 MPH
96H 06/0600Z 38.5N 165.0W 50 KT 60 MPH
120H 07/0600Z 44.0N 163.5W 50 KT 60 MPH
$$
FORECASTER JACOBSON
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