Tropical Storm VONGFONG Advisory Di, 12.05.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 01W (ONE) WARNING
NR 002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION (TD) 01W (ONE), LOCATED APPROXIMATELY 531
NM EAST-SOUTHEAST OF MANILA, PHILIPPINES, HAS TRACKED NORTHWARD AT
05 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY SHOWS THAT OVER THE PAST FEW HOURS, FLARING CONVECTION WITH
OVERSHOOTING TOPS HAS DEVELOPED NEAR THE ASSESSED LLCC, WITH
SOMEWHAT SHALLOWER CONVECTIVE BANDS EXPANDING ACROSS THE SOUTHERN
HEMISPHERE OF THE CIRCULATION. THE INITIAL POSITION IS PLACED WITH
HIGH CONFIDENCE BASED ON EXTRAPOLATION OF A 2225Z DMSP COLOR 37 GHZ
MICROWAVE IMAGE AND A 2356Z ASCAT-B SCATTEROMETER BULLSEYE PASS.
THE INITIAL INTENSITY OF 30 KNOTS IS ASSESSED WITH HIGH CONFIDENCE
BASED ON DVORAK CURRENT INTENSITY ESTIMATES OF T1.5 (25-30KTS) FROM
BOTH PGTW AND RJTD, HEDGED SLIGHTLY HIGHER IN LIGHT OF AN ADVANCED
DVORAK TECHNIQUE ESTIMATE OF T2.0 (30 KNOTS) AND THE AFOREMENTIONED
ASCAT PASS INDICATING 30 KNOT WINDS IN THE SOUTHEAST QUADRANT.
ENVIRONMENTAL ANALYSIS REVEALS THAT TD 01W LIES IN A FAVORABLE
ENVIRONMENT WITH LOW (10-15KT) VWS, MODERATE RADIAL OUTFLOW, BIASED
TO THE EQUATORWARD SIDE PROVIDED BY A WEAK POINT SOURCE 429244OVER
THE SYSTEM AND WARM (28-29C) SEA SURFACE TEMPERATURES (SSTS). THE
CYCLONE IS TRACKING ALONG THE WESTERN PERIPHERY OF A DEEP-LAYERED
SUBTROPICAL RIDGE (STR) CENTERED OVER THE NORTHERN MARIANAS ISLANDS
WITH A NORTH-SOUTH ORIENTED AXIS ALONG ROUGHLY 145E LONGITUDE.
3. FORECAST REASONING.
   A.  THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY
FROM THE LAST PROGNOSTIC REASONING MESSAGE.
   B. OVER THE NEXT 12 HOURS TD 01W WILL TRACK GENERALLY NORTH TO
NORTHWESTWARD ALONG THE WESTERN EDGE OF THE DEEP-LAYER STR CURRENTLY
CENTER NORTH OF GUAM. AFTER THIS POINT THE STR BEGINS TO REORIENT
ONTO A GENERALLY EAST-WEST ORIENTATION WHILST RE-CENTERING NEAR 20N
130E. THIS MOVEMENT WILL RESULT IN TD 01W MOVING ONTO A MORE
WESTERLY TRACK TOWARDS THE CENTRAL PHILIPPINES THROUGH TAU 72. THE
SYSTEM IS FORECAST TO SKIRT THE NORTHERN COAST OF SAMAR AND MAKE
LANDFALL ON THE EXTREME SOUTHEASTERN COAST OF LUZON BY AROUND TAU
60. THE ENVIRONMENT IS EXPECTED TO REMAIN FAVORABLE THROUGH TAU 72,
WITH THE UPPER LEVEL POINT SOURCE REMAINING OVERHEAD THE LLCC
PROVIDING STRONG RADIAL OUTFLOW AND LOW VWS. FLOW OUT OF A TROPICAL
UPPER-TROPOSPHERIC TROUGH (TUTT) CELL LOCATED IN THE SOUTH CHINA IS
CURRENTLY IMPINGING ON THE OUTFLOW TO THE NORTHWEST OF THE SYSTEM.
HOWEVER, THIS TUTT CELL IS FORECAST TO WEAKEN AND MOVE SOUTH,
DECREASING THE PRESSURE ON THE NORTHWEST SIDE AND ALLOWING FOR
INCREASED POLEWARD OUTFLOW, PROVIDING FUEL FOR A PERIOD OF RAPID
INTENSIFICATION BETWEEN TAU 24 AND TAU 48. THE PEAK INTENSITY OF 70
KNOTS IS FORECAST TO OCCUR AT TAU 72. THE ACTUAL PEAK WILL LIKELY
OCCUR AROUND TAU 60 WHILE THE SYSTEM IS STILL OVER WATER AND BE
CLOSER TO 75 KNOTS.
C. AFTER LANDFALL AROUND TAU 60, TD 01W IS FORECAST TO TRACK
NORTHWESTWARD THEN NORTHWARD UNDER THE STEERING INFLUENCE OF THE STR
AS IT MOVES EAST-SOUTHEAST. AFTER MAKING A SECOND LANDFALL ALONG THE
EAST COAST OF NORTHERN LUZON, TD 01W WILL MOVE NORTH AND AGAIN
EMERGE OVER WATER IN THE BASHI CHANNEL BY TAU 120. AFTER THE INITIAL
LANDFALL AND TRANSIT OVER LAND, THE SYSTEM WILL WEAKEN
SIGNIFICANTLY, BUT STRONG POLEWARD OUTFLOW INTO DEEP WESTERLY FLOW
TO THE NORTH WILL ALLOW TD 01W TO MAINTAIN WEAK TROPICAL STORM
STRENGTH EVEN WHILE OVER LAND. NUMERICAL MODEL GUIDANCE HAS COME
INTO MUCH BETTER AGREEMENT SINCE THE PREVIOUS RUN, WITH ALL
AVAILABLE MODELS IN STRONG AGREEMENT (<70NM SPREAD) THROUGH TAU 72.
SIGNIFICANT DIVERGENCE IN MODEL SOLUTIONS DEVELOPS BEYOND TAU 96,
WITH SPREAD BETWEEN OUTLIERS INCREASING TO 320 NM BY TAU 120, AS THE
EXACT NATURE OF THE REORIENTATION AND MOVEMENT OF THE STR VARIES
BETWEEN MODEL SOLUTIONS. THE JTWC FORECAST TRACK CONTINUES TO LIE
JUST NORTH OF THE MULTI-MODEL CONSENSUS, AMONGST THE TIGHTEST
PACKING OF AVAILABLE TRACKERS. WITH THE IMPROVED AGREEMENT IN THE
GUIDANCE, THERE IS INCREASING CONFIDENCE IN THE JTWC FORECAST BUT
CONFIDENCE IS STILL LOW DUE TO THE STILL DEVELOPING NATURE OF THE
SYSTEM.//
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