Tropical Storm THIRTYFIVE Advisory 12月30日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 35W (THIRTYFIVE)
WARNING NR 22//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION (TD) 35W (THIRTYFIVE), LOCATED APPROXIMATELY
366 NM SOUTH OF MANILA, PHILIPPINES, HAS TRACKED WEST-SOUTHWESTWARD
AT 08 KNOTS OVER THE PAST SIX HOURS. TD 35W HAS BEEN RELOCATED
APPROXIMATELY 225NM SOUTH-SOUTHWEST OF THE PREVIOUS WARNING'S
INITIAL POSITION (AT 29/12Z) BASED PRIMARILY ON A 291333Z ASCAT
BULLSEYE SHOWING AN ELONGATED, DEFINED CIRCULATION WITH 25 TO 30
KNOT NORTHEASTERLY WINDS OVER THE WESTERN SEMICIRCLE AND 10 TO 15
KNOTS ELSEWHERE. ADDITIONALLY, SURFACE OBSERVATIONS, ANIMATED
ENHANCED INFRARED (EIR) SATELLITE IMAGERY, TOTAL PRECIPITABLE WATER
IMAGERY, AND ALL AGENCY DVORAK FIXES SUPPORT THE CURRENT POSITION.
CURRENTLY, EIR IMAGERY SHOWS EXPOSED, SHALLOW BANDING WRAPPING INTO
A WEAKLY-DEFINED LOW-LEVEL CIRCULATION CENTER (LLCC) WITH FLARING
CONVECTION OVER THE WESTERN SEMICIRCLE. A 291737Z AMSR2 89GHZ IMAGE
INDICATES FRAGMENTED DEEP CONVECTIVE BANDING OVER THE NORTHWEST
QUADRANT WITH SHALLOW BANDING WRAPPING AROUND THE EASTERN AND
NORTHERN SEMICIRCLES OF THE COMPACT SYSTEM. OVERALL, THE SYSTEM IS
ASSESSED CONSERVATIVELY AT 25 KNOTS BASED ON THE ASCAT AND A RJTD
DVORAK INTENSITY ESTIMATE OF T1.5 (25 KNOTS), HOWEVER, THE SYSTEM IS
CLEARLY A BORDERLINE TD. BASED ON THE AFOREMENTIONED ASCAT IMAGE
SHOWING EXTENSIVE NORTHEASTERLY SURGE WINDS WEST OF THE NORTHERN AND
CENTRAL PHILIPPINES AND THE DEFINED CIRCULATION OVER THE SULU SEA,
THERE IS FAIR CONFIDENCE (WITHIN 45NM) IN THE CURRENT POSITION.
UPPER-LEVEL ANALYSIS INDICATES A MARGINAL ENVIRONMENT WITH STRONG
(25 TO 30 KNOTS) SOUTHEASTERLY VERTICAL WIND SHEAR (VWS) OFFSET BY
STRONG DIFFLUENCE ALOFT. AFTER TURNING SHARPLY SOUTH-SOUTHWESTWARD
(29/00-12Z), TD 35W APPEARS TO BE TRACKING SLOWLY WEST-SOUTHWESTWARD
ALONG THE SOUTHEAST PERIPHERY OF THE LOW-LEVEL SUBTROPICAL RIDGE
(STR), ADJACENT TO A NORTHEAST SURGE EVENT.
3. FORECAST REASONING.
   A. DUE TO THE MAJOR RELOCATION OF THE INITIAL POSITION, THE
OFFICIAL JTWC FORECAST TRACK HAS SHIFTED SOUTH.
   B. TD 35W IS LOCATED WITHIN A COMPLEX STEERING ENVIRONMENT
ADJACENT TO EXTENSIVE NORTHEASTERLY WINDS AND 360NM EAST OF ANOTHER
WEAK LOW PRESSURE AREA (INVEST 97W), THEREFORE, THERE IS HIGH
UNCERTAINTY IN THE JTWC OFFICIAL FORECAST TRACK. THE SYSTEM IS
FORECAST TO TRACK GENERALLY WESTWARD AS IT TRACKS ALONG THE
SOUTHEASTERN PERIPHERY OF THE STR / NORTHEAST SURGE FLOW THROUGH TAU
24. AFTER TAU 24, THE SYSTEM WILL BEGIN TO INTERACT WITH, AND
EVENTUALLY MERGE WITH INVEST 97W. DUE TO THIS INTERACTION AND THE
MARGINAL ENVIRONMENT, TD 35W IS FORECAST TO REMAIN A WEAK TD THROUGH
TAU 72.
   C. AFTER TAU 72, THE NORTHEAST SURGE IS FORECAST TO ABATE AND TD
35W IS FORECAST TO RESUME A WESTWARD TO WEST-NORTHWESTWARD TRACK
UNDER THE STEERING INFLUENCE OF THE LOW-LEVEL STR POSITIONED TO THE
NORTH. VWS IS FORECAST TO DECREASE WITH AN INCREASE IN OCEAN HEAT
CONTENT VALUES AND IMPROVED POLEWARD DIFFLUENCE, WHICH SHOULD ALLOW
THE SYSTEM TO GRADUALLY INTENSIFY TO TROPICAL STORM STRENGTH BY TAU
120. DUE TO THE VERY COMPLEX STEERING ENVIRONMENT, POTENTIAL MERGER
WITH INVEST 97W, AND SPARSE NUMERICAL MODEL GUIDANCE, THERE IS HIGH
UNCERTAINTY IN THE JTWC OFFICIAL FORECAST TRACK.//
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