SUPER TYPHOON NIDA RE-INTENSIFY INTO CATEGORY 5

TROPICAL CYCLONE ADVISORY
NOV 28 2009

STEERING ENVIRONMENT
WIND AND PRESSURE

THERMAL IR IMAGERY
4 FRAME IMAGERY
CLOSEUP EYE IMAGERY

SUPER TYPHOON NIDA (26W)

CATEGORY 5

CURRENT INTENSITY: MAX: 145kt GUST: 175kt (269-324kph)
CURRENT PRESSURE: 914MB
SURFACE WIND ANALYSIS: 150KT (278KPH) MSLP: 876.5MB
ADVANCE DVORAK TECHNIQUES (ADT): 140.0KT(259KPH) MSLP: 899.6MB
CENTRAL REGION TEMP: -1.1C (EYE)
CENTRAL CLOUD TEMP: -74.2C (+35MM/HR)
FORECAST 12HRS: 140KT/259KPH

DISCUSSION:

SUPER TYPHOON (STY) 26W (NIDA), LOCATED APPROXIMATELY 365 NM SOUTH-SOUTHWEST OF IWO TO, HAS TRACKED NORTH-NORTHEASTWARD AT 03 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS A 23-NM EYE. A 272154Z SSMI/S IMAGE CONTINUES TO SUPPORT AN EYEWALL REPLACEMENT CYCLE WITH CONCENTRIC EYEWALLS; THE OUTER EYEWALL HAS CONSOLIDATED AND CONTRACTED SLIGHTLY OVER THE PAST 12 HOURS. ANIMATED WATER VAPOR IMAGERY INDICATES EXCELLENT RADIAL OUTFLOW WITH IMPROVED POLEWARD OUTFLOW OVER THE PAST 12 HOURS, ENHANCED BY MIDLATITUDE WESTERLIES. STY 26W HAS GENERALLY TRACKED NORTHWARD AND SLOWED TO 03 KNOTS WITH INCREASINGLY ERRATIC, TROCHOIDAL MOTION. THE CURRENT INTENSITY IS BASED ON THE HIGHER END OF DVORAK ESTIMATES RANGING FROM 127 (RJTD, KNES) TO 155 KNOTS (PGTW). THE LATEST 500MB ANALYSIS DEPICTS A POLEWARD-ORIENTED, MID-LEVEL SUBTROPICAL RIDGE (STR) POSITIONED EAST OF THE SYSTEM WITH MIDLATITUDE WESTERLIES NORTH OF 25N; STY 26W IS LOCATED WITHIN A REALTIVELY WEAK STEERING ENVIRONMENT BETWEEN THE EASTERN, DOMINANT STR AND THE WESTERN STR, WHICH EXTENDS FROM HAINAN EASTWARD TO ABOUT 130E

FORECAST REASONING.
A. THE FORECAST PHILOSOPHY HAS CHANGED SIGNIFICANTLY WITH A LARGE DECREASE IN TRACK SPEEDS THROUGHOUT THE FORECAST. REASONING WILL BE DISCUSSED BELOW.
B. THE STY 26W IS TRACKING STEADILY AND ERRATICALLY NORTHWARD ALONG THE WESTERN PERIPHERY OF THE MID-LEVEL STR WITHIN A WEAK STEERING ENVIRONMENT. OVERALL, MODEL GUIDANCE IS IN VERY POOR AGREEMENT WITH A TREND TOWARD DISAGREEMENT. THE ECMWF HAS SHIFTED TO A SLOW WESTWARD TRACK; THE GFS SHOWS A SHORT-TERM NORTHWARD MOVEMENT THEN SHARP TURN SOUTHWESTWARD; UKMO AND TC-LAPS SHOW A SLOW NORTHWARD TRACK; THE JGSM INDICATES A VERY SLOW WESTWARD DRIFT; AND WBAR, GFDN AND NOGAPS ALL SHOW A RE-CURVE WITH WIDELY VARYING TRACK SPEEDS. IN ADDITION TO THESE TRACK DIFFERENCES, THE MODELS ALSO SHOW FORECAST INTENSITY DIFFERENCES. THE ECMWF AND GFS INDICATE 120 PLUS INTENSITIES THROUGH TAU 120, POSSIBLY INDICATING A TRACK WESTWARD UNDER A STRENGTHENING WESTERN STR VICE RAPID WEAKENING WITHIN THE STRONG LOW-LEVEL NORTHEASTERLY FLOW. NOGAPS IS PARTICULARLY PROBLEMATIC WITH 160 PLUS KNOT INTENSITY THROUGH TAU 120 AS THE SYSTEM TRACKS UNDER 100 PLUS KNOTS OF VERTICAL WIND SHEAR (VWS) AND DIRECTLY UNDER THE JET; ADDITIONALLY, THE LOW-LEVEL CIRCULATION CENTER REMAINS VERTICALLY STACKED WHILE COMPLETING EXTRA-TROPICAL TRANSITION (ETT). THEREFORE, THE NOGAPS EXCESSIVE TRACK SPEEDS AND DEPICTION OF THE ETT APPEAR ERRONEOUS. GFDN, HOWEVER, DEPICTS A MORE TYPICAL WEAKENING TREND AND SLOWER TRACK SPEEDS. THIS FORECAST CONTINUES TO FAVOR THE RE-CURVATURE SCENARIO BASED ON THE ANALYSIS OF THE EASTERN STR ALBEIT WITH SLOW TRACK SPEEDS THROUGH TAU 48 AND SLIGHT ACCELERATION THROUGH TAU 72 DUE TO THE WEAK STEERING ENVIRONMENT. STY 26W IS FORECAST TO MAINTAIN STY STRENGTH THROUGH THE NEXT 12-24 HOURS, THEN WEAKEN QUICKLY DUE TO STRONG VWS AND LOWER OCEAN HEAT CONTENT/SST.
C. IN THE EXTENDED TAUS, THERE IS GREATER UNCERTAINTY WITH POOR
AGREEMENT BETWEEN THE AVAILABLE MODEL TRACKERS. THERE IS A POSSIBILITY THAT THE SYSTEM MAY WEAKEN AND DISSIPATE PRIOR TO COMPLETING ETT AND EITHER SLOW IN FORWARD MOTION OR TRACK UNDER THE STRONG LOW-LEVEL NORTHEASTERLY FLOW BACK TO THE SOUTHWEST. THIS ALTERNATE SCENARIO IS BASED ON THE LOW-LEVEL STR BUILDING EASTWARD, NORTH OF THE SYSTEM, AS IDENTIFIED IN SEVERAL MODELS, AND THE SYSTEM TRACKING ALONG THE SOUTHERN EDGE OF THE BAROCLINIC ZONE WHILE WEAKENING RAPIDLY.

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