Tropical Storm KAI-TAK Advisory 12月14日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 32W (THIRTYTWO)
WARNING NR 01//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION (TD) 32W (THIRTYTWO), LOCATED APPROXIMATELY
418NM EAST-SOUTHEAST OF MANILA, PHILIPPINES, HAS TRACKED WEST-
NORTHWESTWARD AT 6 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED
INFRARED (EIR) SATELLITE IMAGERY SHOWS POORLY ORGANIZED, FRAGMENTED,
FORMATIVE CONVECTIVE BANDS LOOSELY FEEDING INTO A WEAK AND SOMEWHAT
DIFFUSE LOW LEVEL CIRCULATION CENTER (LLCC). THE INITIAL POSITION IS
PLACED WITH MODERATE CONFIDENCE BASED ON THE EIR ANIMATION AND
ANALYSIS OF RADAR MOSAIC DATA FROM THE PHILIPPINES. THE ASSESSED
LLCC LINES UP WITH THE ANALYZED POSITION EXTRAPOLATED FROM A LOW
REFLECTIVITY NOTCH FEATURE IN THE 131326Z AMSU-B MICROWAVE PASS. THE
INITIAL INTENSITY OF 25 KNOTS IS BASED ON AN OVERALL ASSESSMENT OF
AGENCY AND OBJECTIVE DVORAK ESTIMATES OF T1.5 (25 KNOTS) FROM KNES
AND RJTD AND T1.0 (20-25 KNOTS) FROM PGTW. INITIAL INTENSITY IS
SUPPORTED BY A 131243Z OSCAT PASS INDICATING 25-30 KNOT WINDS ALONG
THE WESTERN PERIPHERY OF THE STORM, WITH 20-25 KNOT WINDS ALONG THE
SOUTHERN SIDE. SOME HIGHER WIND SPEEDS EXCEEDING 35 KNOTS ARE
PRESENT FAR TO THE NORTH OF THE SYSTEM BUT ARE NOT DIRECTLY
ASSOCIATED WITH TD 32W. ENVIRONMENTAL ANALYSIS INDICATES TD 32W IS
IN A NARROW BAND OF LOW (5-10 KNOTS) VERTICAL WIND SHEAR (VWS)
PROVIDED BY AN UPPER-LEVEL POINT SOURCE THAT IS NEARLY DIRECTLY OVER
THE LLCC. THE UPPER-LEVEL FLOW PATTERN IS PROVIDING ROBUST POLEWARD
AND WESTWARD EXHAUST FOR THE SYSTEM, AND SEA SURFACE TEMPERATURES IN
THE AREA SUPPORTIVE AT 28-29 DEG CELSIUS. THESE FAVORABLE DYNAMICS
ARE BEING OFFSET, HOWEVER, BY ENTRAINMENT OF RELATIVELY COOL, DRY
NORTHEASTERLY FLOW FROM A COLD SURGE EVENT. THE CYCLONE IS CURRENTLY
LIES WITHIN A COL AREA BETWEEN SUBTROPICAL RIDGES (STR) NEAR WAKE
ISLAND AND IN THE BAY OF BENGAL AND A NEAR EQUATORIAL RIDGE (NER)
OVER WESTERN NEW GUINEA, LEADING TO SLOW, MEANDERING MOVEMENT.
3. FORECAST REASONING.
   A. THIS IS THE INITIAL PROGNOSTIC REASONING MESSAGE AND SETS THE
FORECAST PHILOSOPHY FOR THIS SYSTEM.
   B. TD 32W IS EXPECTED TO CONTINUE TO MEANDER GENERALLY
NORTHWESTWARD ALONG THE EASTERN COAST OF SAMAR FOR THE NEXT 48 HOURS
AS THE WEAK STEERING PATTERN PERSISTS. BEYOND TAU 48, THE STR OVER
THE WESTERN PACIFIC BUILDS WESTWARD AND BECOMES THE PRIMARY STEERING
RIDGE AND DRIVES TD 32W ONTO A WESTWARD TRACK. THE OVERALL FAVORABLE
VWS AND OUTFLOW CONDITIONS CONTINUE TO BE HINDERED BY THE
ENTRAINMENT OF COOLER, DRIER AIR AND INTERACTION WITH THE PHILIPPINE
ISLANDS, SUPPORTING MINIMAL INTENSIFICATION, PEAKING AT 35 KNOTS
PRIOR TO CROSSING OVER THE CENTRAL PHILIPPINES BEYOND TAU 72.
DYNAMIC MODEL GUIDANCE IS IN OVERALL POOR AGREEMENT WITH THE AFUM,
EGRR AND CTCX TRACKERS TURNING THE SYSTEM NORTH-NORTHEAST THROUGH
TAU 72, BEFORE HEADING WEST, WHILE THE ECMWF, GFS AND HWRF TRACKERS
SHOW A QUASI-STATIONARY PERIOD THROUGH THE FIRST 48 HOURS, THEN WEST-
NORTHWEST. THE JTWC TRACK THROUGH TAU 72 LIES SOUTH OF THE MULTI-
MODEL CONSENSUS AND GIVEN THE NEAR-TERM UNCERTAINTY, THERE IS LOW
CONFIDENCE IN THE JTWC TRACK FORECAST.
   C. BEYOND TAU 72, THE AFOREMENTIONED STEERING RIDGE REMAINS IN
PLACE OVER THE WESTPAC WITH A STRONG RIDGE EXTENSION ALONG ROUGHLY
20 DEG NORTH, AND WILL KEEP TD 32W ON A GENERALLY WESTWARD ACROSS
THE CENTRAL PHILIPPINES BEFORE REEMERGING INTO THE SOUTH CHINA SEA
AROUND TAU 100. TD 32W WILL WEAKEN AS IT CROSSES THE PHILIPPINES AS
INTERACTION WITH THE LOCAL TERRAIN WILL DISRUPT VORTEX INFLOW, WHILE
UPPER-LEVEL MASS CONVERGENCE FROM OUTFLOW ASSOCIATED WITH INVEST 97W
AS IT DEVELOPS, WILL SERVE TO OFFSET THE CONTINUED LOW VWS
ENVIRONMENT. NUMERICAL GUIDANCE IS IN BETTER AGREEMENT IN THE LATER
TAUS, WITH ALL AVAILABLE TRACKERS INDICATING A WEST-SOUTHWESTWARD
TRACK THROUGH THE END OF THE FORECAST PERIOD. THE EXCEPTIONS ARE THE
PREVIOUSLY MENTIONED MODELS TAKING THE SYSTEM TO THE NORTH AND
DISSIPATING IT. WITH THE OVERALL UNCERTAINTY IN THE NUMERICAL
GUIDANCE, THERE IS LOW CONFIDENCE IN THIS PORTION OF THE JTWC
FORECAST TRACK.//
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