WTPA42 PHFO 221450 TCDCP2 HURRICANE NEKI DISCUSSION NUMBER 16 NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI CP032009 500 AM HST THU OCT 22 2009 HURRICANE NEKI REACHED PEAK INTENSITY LAST NIGHT AND HAS BEGUN TO WEAKEN...ALTHOUGH ONLY EVER SO SLIGHTLY THIS MORNING. FIXES FROM PHFO AND JTWC GAVE CI VALUES OF 5.5 AND 5.0 WHILE SAB GAVE 6.0...WITH JTWC REPORTING THE INTENSITY DROP OVER THE PAST 6 HOURS. SATELLITE LOOP SHOWS A CONTINUED CLOUD-FILLED EYE AND A BIT OF EROSION INTO THE EYEWALL ALONG ITS SOUTHEAST FLANK. THE INITIAL INTENSITY IS SET AT 100 KT AS A COMPROMISE BETWEEN PHFO AND JTWC INTENSITIES. OUTFLOW HAS BECOME HAMPERED ALONG THE SOUTHWEST FLANK...BUT REMAINS GOOD ELSEWHERE. SOUTHWEST SHEAR IS INCREASING...WITH THE 1200 UTC UW-CIMSS VERTICAL SHEAR PRODUCT NOW SHOWING OVER 25 KT OF SHEAR. THIS APPEARS TO BE MORE THAN ENOUGH TO AFFECT THE CORE. NEKI REMAINS OVER 28 DEGREE C WATER...BUT THANKS TO THE SHEAR GRADUAL WEAKENING IS EXPECTED. THE CENTER OF NEKI IS OFF THE WESTERN LIMB OF THE CLOSEST SCATTEROMETER PASS...BUT IT SEEMS CLEAR THAT THE 34 KT WIND RADIUS IS CONSIDERABLY LESS THAN IT WAS 12 TO 24 HOURS AGO...ESPECIALLY IN THE NORTHEAST QUADRANT. THIS RADIUS HAS BEEN TRIMMED BACK TO 180 NM FOR THIS BULLETIN CYCLE. NEKI ALSO REACHED THE WESTERNMOST POINT OF ITS TRACK LAST NIGHT...WITH A SLIGHTLY MORE PRONOUNCED EAST COMPONENT NOTED IN LAST 6 HOUR MOTION. INITIAL MOTION IS SET AT 020 DEGREES AT 9 KT. A FRONT MOVING SOUTHEASTWARD NEAR LISIANSKI IS ERODING THE SUBTROPICAL RIDGE...URGING NEKI TO GAIN LATITUDE. NEKI IS EXPECTED TO GRADUALLY SHIFT TO A MORE NORTHEASTERLY TRACK AS IT INTERACTS WITH THE ENCROACHING FRONT AND ITS ASSOCIATED UPPER LEVEL TROUGH. TRACK GUIDANCE SEEMS TO BE HAVING TROUBLE HANDLING THE RECURVATURE OF NEKI THIS TIME AROUND...WITH ALL BUT BAMD IGNORING THE PAST 6 AND 12 HOURS MOTION AND WANTING TO KEEP MOVING NEKI DUE NORTH...AT LEAST INITIALLY. THE FORECAST TRACK FOLLOWS BAMD THROUGH 24 HOURS...THEN EASES INTO AN ARC PARALLEL TO AND JUST RIGHT OF GFDL AND HWRF. THE FORECAST TRACK IS THEREFORE ALSO SLIGHTLY TO THE RIGHT OF THE PREVIOUS ONE. NEKI WILL REMAIN IN 26 C OR WARMER WATER THROUGH 48 HOURS...THEN MOVE ACROSS COOLER WATER THROUGH THE REST OF ITS FORECAST TRACK. HOWEVER...UW-CIMSS NOW SHOWS UNFAVORABLE SHEAR IMPACT ON THIS SYSTEM THROUGH 24 HOURS. NEKI IS FORECAST TO WEAKEN TO A TROPICAL STORM AFTER 72 HOURS...THEN TO A DEPRESSION AT 120 HOURS. THE LONG RANGE INTENSITY FORECAST MAY CHANGE DEPENDING ON HOW NEKI INTERACTS WITH THE FRONT AND UPPER TROUGH. ON ITS CURRENT TRACK...NEKI WILL BE APPROACHING THE PAPAHANAUMOKUAKEA NATIONAL MONUMENT BETWEEN FRENCH FRIGATE SHOALS AND NIHOA ON FRIDAY...AND A HURRICANE WARNING REMAINS FOR THE MONUMENT FROM NIHOA ISLAND TO MARO REEF. THE TROPICAL STORM WATCH FROM MARO REEF TO LISIANSKI HAS BEEN CANCELLED. LARGE SWELLS FROM THE SOUTH WILL BUILD AND CONDITIONS WILL DETERIORATE ACROSS PORTIONS OF THE WARNING AREA TODAY...WITH SEAS GREATER THAN 20 FT AND SURF UP 25 FT EXPECTED. FORECAST POSITIONS AND MAX WINDS INITIAL 22/1500Z 20.4N 166.0W 100 KT 12HR VT 23/0000Z 21.7N 165.5W 100 KT 24HR VT 23/1200Z 23.4N 164.8W 95 KT 36HR VT 24/0000Z 24.9N 163.9W 85 KT 48HR VT 24/1200Z 26.4N 162.7W 75 KT 72HR VT 25/1200Z 29.3N 160.4W 65 KT 96HR VT 26/1200Z 32.7N 157.3W 50 KT 120HR VT 27/1200Z 36.4N 153.4W 30 KT $$ FORECASTER POWELL