Tropical Storm PAKHAR Advisory lun, 12-12

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 29W (TWENTYNINE) WARNING
NR 003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
   INITIAL POSITION: 17.4N 126.2E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 344 NM EAST-NORTHEAST OF MANILA,
PHILIPPINES
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 13 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) INDICATES THAT TS
29W (TWENTYNINE) REMAINS A BIT DISORGANIZED, THOUGH IT APPEARS TO
BE MAKING A RUN AT CONSOLIDATION. THE LOW LEVEL CIRCULATION CENTER
(LLCC) REMAINS PARTIALLY EXPOSED, WITH THE CENTER OBSCURED UNDER
SOME CONVECTIVE BLOWOFF AND THE NORTHEASTERN LOW-LEVEL BANDS
EVIDENT IN CLEAR AIR TO THE NORTHEAST. A SURFACE BOUNDARY LIES TO
THE NORTH NEAR 22N, ACCOMPANIED BY A VERY SHARP VWS BOUNDARY.
VORTICAL HOT TOWERS (VHTS) ARE SEEN TO BE FLARING UP ACROSS THE
SOUTHERN PERIPHERY AS WELL AS TO THE NORTH, BUT AS OF YET, HAVE NOT
CONSOLIDATED AND THE SYSTEM IS STILL NOT VERTICALLY ALIGNED. A
110507Z ATMS 183GHZ MICROWAVE IMAGE PROVIDED ADDITIONAL SUPPORT TO
THE ASSESSMENT OF MISALIGNED VORTEX, WITH THE LOWER-LEVEL VORTEX
OUT FRONT (NORTHEAST) OF THE DEVELOPING UPPER-LEVEL VORTEX, WHICH
APPEARED AS A NASCENT MICROWAVE EYE-LIKE FEATURE IN THE MICROWAVE
IMAGE. THE INITIAL POSITION IS ASSESSED WITH MEDIUM CONFIDENCE
BASED ON THE ATMS IMAGE AND THE CONGRUENCE OF THE MAJORITY OF
AGENCY POSITION FIXES. THE INITIAL INTENSITY IS INCREASED TO 35
KNOTS WITH MEDIUM CONFIDENCE, AS THE AVAILABLE INTENSITY ESTIMATES
ARE EVENLY SPLIT BETWEEN 30 KNOTS AND 35 KNOTS AND THE INTENSITY IS
HEDGED UPWARDS, TOWARDS THE SATCON AND AIDT. THE ENVIRONMENT IS
GENERALLY FAVORABLE, WITH AN UPPER-LEVEL POINT SOURCE DIRECTLY OVER
TOP OF THE LLCC PROVIDING FOR GOOD RADIAL OUTFLOW AND VERY LOW
VERTICAL WIND SHEAR (VWS). THE SYSTEM IS TRACKING NORTHEASTWARD
ALONG THE NORTHWEST PERIPHERY OF A DEEP-LAYER SUBTROPICAL RIDGE
(STR) TO THE EAST.
INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK
CURRENT STEERING MECHANISM: NORTHWESTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) CENTERED FAR TO THE EAST.
AGENCY DVORAK AND AUTOMATED FIXES:
   PGTW: T2.0 - 30 KTS
   RJTD: T1.5 - 25 KTS
   KNES: T2.5 - 35 KTS
   CIMSS SATCON: 35 KTS AT 110505Z
   CIMSS ADT: 33 KTS AT 110540Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 0-5 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: WEAK RADIAL
ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: LOW
3. FORECAST REASONING.
SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.
FORECAST DISCUSSION: AS MENTIONED ABOVE, A SURFACE STATIONARY FRONT
LIES DRAPED ACROSS THE REGION FROM ABOUT 22N 133E EXTENDING FAR TO
THE NORTHEAST TO A LOW PRESSURE AREA NEAR 32N 160E. THROUGH THE
FIRST 24 HOURS OF THE FORECAST, TS 29W WILL CONTINUE TO TRACK
NORTHEASTWARD ALONG THE NORTHWEST SIDE OF A STRONG, DEEP-LAYER STR
WHICH IS CENTERED NEAR 20N 160E AND GENERALLY PARALLEL TO THE
SURFACE BOUNDARY. WHILE CURRENTLY MISALIGNED IN THE VERTICAL, IF
THE SYSTEM CAN TAKE ADVANTAGE OF THE CURRENT LOW-SHEAR ENVIRONMENT,
CONSOLIDATE AND VERTICALLY ALIGN, ENVIRONMENTAL CONDITIONS ARE
FAVORABLE FOR INTENSIFICATION THROUGH THE NEXT 24 HOURS. THE SYSTEM
IS CURRENTLY ANTICIPATED TO PEAK AT 45 KNOTS BY TAU 24, THOUGH SOME
OF THE GUIDANCE SUGGESTS A PEAK CLOSER TO 50 KNOTS. AT THIS POINT
THE SYSTEM WILL BE NEAR 20N, WHERE IT WILL ENCOUNTER THE SHARP
SHEAR GRADIENT, WHICH WILL BE ITS ULTIMATE DEMISE. AFTER TAU 24
SHEAR WILL INCREASE DRAMATICALLY AND DECAPITATE TS 29W.
SIMULTANEOUSLY THE SYSTEM WILL BE ENGULFED IN DRY LOW AND MID-LEVEL
AIR FLOWING DOWN FROM THE NORTH AND BEGIN TO RAPIDLY WEAKEN. AS IT
DOES SO, IT WILL GRADUALLY COME UNDER THE INFLUENCE OF
PROGRESSIVELY LOWER-LEVEL STEERING FLOWS, AND SHARPLY CURVE TO THE
SOUTH-SOUTHWEST BY TAU 72 AS THE STRONG NORTHEASTERLY FLOW COMES TO
DOMINATE THE STEERING. THE SYSTEM WILL DISSIPATE AS A TROPICAL
CYCLONE NO LATER THAN TAU 72, THOUGH IT IS POSSIBLE IT COULD
DISSIPATE A BIT EARLIER, NEAR TAU 60.
MODEL DISCUSSION: DETERMINISTIC AND ENSEMBLE TRACK GUIDANCE IS IN
GOOD OVERALL AGREEMENT THROUGH TAU 24 WITH ALL AVAILABLE MODELS
SUPPORTING A TRACK TO THE NORTHEAST. BUT AFTER TAU 24, ONCE THE
WEAKENING TREND STARTS, THE MODELS DIVERGE SIGNIFICANTLY. MOST OF
THE GLOBAL MODELS, INCLUDING THE ENSEMBLES, SUPPORT THE JTWC
FORECAST, SHOWING THE SYSTEM TURNING TO THE SOUTH IN A GRADUAL ARC
AFTER TAU 24. THE MAIN DIFFERENCE IS IN THE TIMING AND SHARPNESS OF
THE TURN, WITH THE GFS BEING THE MOST AGGRESSIVE, WHILE THE ECMWF IS
MUCH MORE GRADUAL. MEANWHILE THE MESOSCALE MODELS AND THE NAVGEM
JUMP VORTEXES AFTER TAU 48, AND TRACK A DEVELOPING BAROCLINIC LOW
MOVING QUICKLY NORTHEAST ALONG THE FRONTAL BOUNDARY. THE JTWC
FORECAST STICKS WITH THE SEPARATION SCENARIO, AND TURNS THE SYSTEM
TO THE SOUTH, THOUGH CONFIDENCE IS MEDIUM DUE TO THE VERY LARGE
SPREAD IN THE GUIDANCE AND THE HIGHLY UNCERTAIN TRACK DURING AND
AFTER THE WEAKENING PHASE. INTENSITY GUIDANCE IS MORE TIGHTLY
PACKED, WITH ALL GUIDANCE INDICATING A PEAK AT TAU 24, WITH AN
INTENSITY BETWEEN 35 AND 47 KNOTS, FOLLOWED BY A RAPID WEAKENING.
THE JTWC FORECAST IS SLIGHTLY ABOVE THE CONSENSUS THROUGH THE
FORECAST PERIOD WITH HIGH CONFIDENCE.
FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   INTENSITY 0 - 72 HR: HIGH//
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