Tropical Storm VAMCO Advisory Mon Nov 09

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 25W (VAMCO)
WARNING NR 002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION 25W (VAMCO), LOCATED APPROXIMATELY 537 NM
EAST-SOUTHEAST OF MANILA, PHILIPPINES, HAS TRACKED NORTHWESTWARD AT
11 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED
SATELLITE IMAGERY (EIR) INDICATES THAT THE SYSTEM IS STILL
STRUGGLING TO CONSOLIDATE, WITH DEEP CONVECTION EXTENDING LINEARLY
ACROSS THE SOUTHERN SEMICIRCLE OF THE OVERALL CIRCULATION AND WEAK
SPIRAL BANDING EXPOSED TO THE NORTH, WRAPPING INTO THE OBSCURED LOW
LEVEL CIRCULATION CENTER (LLCC). LATE RECEIPT OF 091157Z PARTIAL
ASCAT-A AND 091311Z BULLSEYE ASCAT-B PASSES SHOW THAT, WHILE THE
LLCC HAS CONSOLIDATED SIGNIFICANTLY OVER THE 12 HOURS SINCE THE
PREVIOUS SCATTEROMETER PASS, IT IS STILL ELONGATED ALONG A SOUTHWEST-
NORTHEAST AXIS. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE
IN THE NORTHEAST POCKET OF THE AFOREMENTIONED ASCAT DATA. THE
INITIAL INTENSITY IS SET AT 30 KTS WITH HIGH CONFIDENCE BASED ON
MULTI-AGENCY DVORAK INTENSITY ESTIMATES OF T1.5-T2.0 (25-30 KNOTS)
FROM PGTW AND RJTD, AND AN ADVANCED DVORAK TECHNIQUE (ADT) ESTIMATE
OF T2.0. THE PREVIOUSLY MENTIONED ASCAT DATA LENDS SUPPORT TO THE
INTENSITY ESTIMATE, AS THE ASCAT-B PASS IN PARTICULAR SHOWS A BROAD
SWATH OF 30 KNOT WINDS EXTENDING FROM SOUTH TO NORTHEAST OF THE
LLCC, THOUGH ONLY 20 KNOTS WRAPPING ALONG THE WESTERN PERIPHERY. TD
25W IS TRACKING NORTHWESTWARD ALONG THE SOUTHWESTERN PERIPHERY OF A
SUBTROPICAL RIDGE (STR) POSITIONED TO THE NORTHEAST, THROUGH AN
ENVIRONMENT WHICH IS VERY FAVORABLE FOR INTENSIFICATION WITH WARM
(29-30 CELSIUS) SEA SURFACE TEMPERATURES (SST), LOW (5-10 KTS)
VERTICAL WIND SHEAR (VWS), HIGH (120-140 KJ/CM^2) OHC AND STRONG
EQUATORWARD AND MODERATE WESTWARD OUTFLOW.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. IN THE NEAR TERM, TD 25W WILL CONTINUE TO TRACK NORTHWESTWARD
THROUGH TAU 12 BEFORE SLOWLY TURNING ONTO A WESTWARD TRACK BY TAU 36
AS THE STR BUILDS AND EXTENDS TOWARDS THE WEST ROUGHLY ALONG THE
25TH PARALLEL, EFFECTIVELY BLOCKING ANY FURTHER POLEWARD MOVEMENT.
THE SYSTEM IS FORECAST TO CROSS LAMON BAY AND MAKE LANDFALL ALONG
THE CENTRAL LUZON COAST DUE EAST OF MANILA NEAR TAU 60 BEFORE
REEMERGING INTO THE OPEN WATERS OF THE SOUTH CHINA SEA BY TAU 72.
WHILE THE SYSTEM HAS STRUGGLED TO CONSOLIDATE A WELL DEFINED
CONVECTIVE CORE, IT IS EXPECTED THAT THE ENVIRONMENT SHOULD ALLOW
FOR THIS CONSOLIDATION WITHIN THE NEXT 6 TO 12 HOURS RESULTING IN A
RELATIVELY SLOW INTENSIFICATION THROUGH TAU 12. THEREAFTER, A
COMBINATION OF RADIAL OUTFLOW, LOW VWS PROVIDED BY A DEVELOPING
ANTI-CYCLONE OVER THE SYSTEM, AND PASSAGE OVER VERY WARM, HIGH OHC
WATERS WILL ALLOW FOR STEADY INTENSIFICATION THROUGH TAU 24. A
PERIOD OF RAPID INTENSIFICATION IS FORECAST BETWEEN TAUS 24 AND 48
AS THE SYSTEM TRACKS OVER WATERS WITH HIGH OHC VALUES, VWS REMAINS
VERY LOW AND THE UPPER-LEVEL ANTICYCLONE BECOMES VERTICALLY STACKED
OVER THE LLCC, AND THE SYSTEM BEGINS TO TAP INTO A POLEWARD OUTFLOW
CHANNEL. THE FORECAST CALLS FOR A PEAK INTENSITY OF 105 KNOTS AT TAU
48, BUT ADDITIONAL INTENSIFICATION IS POSSIBLE PRIOR TO LANDFALL. AS
THE SYSTEM CROSSES LUZON, INTERACTION WITH THE RUGGED TERRAIN WILL
INDUCE SIGNIFICANT WEAKENING, WITH THE SYSTEM FORECAST TO REEMERGE
INTO THE SOUTH CHINA SEA AS A MINIMAL TYPHOON. DYNAMIC TRACK
GUIDANCE IS IN OVERALL GOOD AGREEMENT THROUGH THE TURN WESTWARD,
WITH SOME SLIGHT DIFFERENCES IN THE SHARPNESS OF THE TURN LEADING TO
A SPREAD OF 85NM AT TAU 48 THROUGH TAU 72, WITH NAVGEM DELINEATING
THE POLEWARD EDGE OF THE ENVELOPE AND JGSM THE EQUATORWARD. THE
TIGHT AGREEMENT IN THE MODEL SOLUTIONS LENDS OVERALL GOOD CONFIDENCE
IN THE INITIAL PORTION OF THE JTWC FORECAST TRACK, LAID ON THE
NORTHERN EDGE OF THE GUIDANCE ENVELOPE THROUGH TAU 48, THEN NEAR THE
MULTI-MODEL CONSENSUS THROUGH TAU 72. INTENSITY GUIDANCE REMAINS
MIXED, WITH A WIDE RANGE OF PEAK INTENSITIES BETWEEN ABOUT 65 KNOTS
AND 90 KNOTS. HWRF REMAINS THE HIGH OUTLIER, BUT HAS COME DOWN A BIT
TO 100 KNOTS PEAK. THE JTWC INTENSITY FORECAST IS HEDGED SLIGHTLY
HIGHER THAN THE HWRF WITH FAIR CONFIDENCE.
   C. AFTER TAU 72, THE SYSTEM WILL CONTINUE TO TRACK WESTWARD
THROUGH TAU 120 UNDER THE STEERING INFLUENCE OF THE DEEP-LAYER STR
TO THE NORTH. ONCE REEMERGING OVER THE OPEN WATERS OF THE SOUTH
CHINA SEA, THE SYSTEM WILL REINTENSIFY TO A PEAK OF 70 KNOTS UNDER
MARGINALLY FAVORABLE ENVIRONMENTAL CONDITIONS. NUMERICAL MODEL
GUIDANCE DEPICTS INCREASING UNCERTAINTY AFTER TAU 72, WITH CROSS-
TRACK SPREAD INCREASING TO 250NM BY TAU 120. THE MAJORITY OF THE
MODELS ARE TIGHTLY GROUPED NEAR THE MULTI-MODEL CONSENSUS, BUT A
GROUPING OF THE NVGM, AFUM, AND UKMET ENSEMBLE CONTINUES TO TRACK
THE SYSTEM NORTH-WESTWARD TOWARDS HAINAN ISLAND. WITH THE INCREASING
UNCERTAINTY AND TWO DISTINCT GROUPINGS WITH INCREASINGLY DIVERGENT
SOLUTIONS, THERE IS OVERALL LOW CONFIDENCE IN THE EXTENDED FORECAST
TRACK, WHICH LIES JUST SOUTH OF THE MULTI-MODEL CONSENSUS.//
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