Tropical Storm THIRTYFIVE Advisory Sat Dec 29

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 35W (THIRTYFIVE)
WARNING NR 20//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION (TD) 35W (THIRTYFIVE), LOCATED APPROXIMATELY
209 NM SOUTHEAST OF MANILA, PHILIPPINES, HAS TRACKED WEST-
NORTHWESTWARD AT 07 KNOTS OVER THE PAST SIX HOURS. ANIMATED
MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A DETERIORATING
SYSTEM, WITH REMNANTS OF A DISSIPATING CENTRAL COLD COVER (CCC)
FEATURE OBSCURING THE LLCC. THE INITIAL POSITION IS BASED ON
ANALYSIS OF A FEW VISIBLE OUTER FEEDER BANDS WHICH ARE FEEDING INTO
THE LLCC, SURFACE OBSERVATIONS FROM THE SURROUNDING REGION AND
PAGASA RADAR LOOPS WITH LOW CONFIDENCE. A 290520Z AMSR2 89 GHZ
COMPOSITE MICROWAVE IMAGE SHOWS SOME DEEP CONVECTION TO THE
NORTHWEST OF THE ASSESSED LLCC, BUT WITH ONLY WEAK CONVECTIVE
BANDING IN ALL OTHER QUADRANTS OF THE SYSTEM. THE INITIAL INTENSITY
REMAINS DIFFICULT TO ASSESS, ESPECIALLY WITH THE FLARING
CONVECTIVE BURSTS OVER THE SYSTEM, HOWEVER, THE INITIAL INTENSITY
HAS BEEN DECREASED SLIGHTLY TO 25 KNOTS BASED ON A PGTW DVORAK
INTENSITY ESTIMATE OF T1.5 (25 KNOTS) AND THE LACK OF ANY SURFACE
OBSERVATIONS OVER 10 KNOTS IN THE REGION. UPPER-LEVEL ANALYSIS
INDICATES A FAVORABLE ENVIRONMENT WITH LOW (15-20 KNOTS) VWS,
MODERATE TO STRONG DIFFLUENCE ALOFT AND POLEWARD OUTFLOW. TD 35W IS
TRACKING WESTWARD UNDER THE STEERING INFLUENCE OF A LOW- TO MID-
LEVEL SUBTROPICAL RIDGE (STR) POSITIONED TO THE NORTH.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. OVER THE NEXT 12 HOURS TD 35W WILL CONTINUE TRACKING GENERALLY
WESTWARD, ALONG THE SOUTHERN PERIPHERY OF THE AFOREMENTIONED STR,
PASSING ACROSS THE SOUTHERN PORTION OF MINDORO, THEN NORTH OF
PALAWAN ISLAND, REEMERGING INTO THE SOUTH CHINA SEA (SCS) BY TAU 24
AS A WEAK DEPRESSION. INTERACTION WITH THE COMPLEX TERRAIN OF THE
PHILIPPINE ARCHIPELAGO WILL LIMIT OPPORTUNITIES FOR INTENSIFICATION
FOR THE NEXT 12-24 HOURS BUT ONCE THE SYSTEM REEMERGES OVER THE OPEN
WATERS OF THE SCS, IT WILL INTENSIFY SLOWLY AS VWS DECREASES. BY TAU
36 THE SYSTEM WILL REACH TROPICAL STORM STRENGTH AND GROW IN OVERALL
SIZE AS IT INTERACTS WITH A LARGE AREA OF GALE FORCE WINDS
ASSOCIATED WITH A NORTHEAST SURGE EVENT. DUE TO THE COMPETING
INFLUENCES OF THE INCREASED SSTS, LOW VWS AND COOLER, DRIER AIR OF
THE SURGE EVENT, TD 35W IS EXPECTED TO MAINTAIN INTENSITY AT 35
KNOTS FROM TAU 36 TO TAU 72. THE BULK OF THE NUMERICAL MODEL
GUIDANCE SUPPORTS THE JTWC FORECAST TRACK, HOWEVER, NVGI IS THE SOLE
NORTHERN OUTLIER, TAKING THE SYSTEM DUE WEST AND DISSIPATING IT BY
TAU 36, WHILE AVNI IS THE SOUTHERN OUTLIER, THOUGH IT MAINTAINS THE
SAME GENERAL SHAPE OF THE TRACK. ANALYSIS OF AVNI, NVGI AND ECMWF
SLP FIELDS SHOW TD 35W TRACKING GENERALLY SOUTHWESTWARD BUT
DISSIPATING BY TAU 24, WHEREBY THE MODELS LOSE TRACK OF THE SYSTEM,
BUT THEN MERGING WITH INVEST AREA 97W, WEST OF BORNEO, AND
REINTENSIFYING. THE OFFICIAL FORECAST MAINTAINS THE SYSTEM AT 35
KNOTS THROUGH THIS PERIOD, AND REFLECTS THE MERGER OF THE TWO
SYSTEMS BY TAU 48. WHILE ALL MODELS BUT NVGI AGREE ON THE TRACK OF
TD 35W, DUE TO THE POTENTIAL FOR DISSIPATION PLUS POSSIBLE
INTERACTION WITH THE SURGE EVENT AND INVEST 97W, THERE IS LOW
CONFIDENCE IN THIS PHASE OF THE FORECAST TRACK.
   C. AFTER TAU 72, TD 35W WILL TURN WESTWARD ALONG WITH
SOUTHWESTERN PERIPHERY OF THE STR TO THE NORTHEAST OF LUZON. BY THIS
POINT IN THE FORECAST, THE SURGE EVENT WILL HAVE WEAKENED ENOUGH
THAT IT WILL HAVE LITTLE IN THE WAY OF FURTHER INFLUENCE ON TD 35W,
ALLOWING IT TO CONSOLIDATE TO THE SOUTHEAST OF VIETNAM. INCREASING
SSTS, DECREASING VWS AND INCREASING OUTFLOW PROVIDED BY A DEVELOPING
UPPER-LEVEL POINT SOURCE, WILL COMBINE TO ALLOW FOR SLOW
INTENSIFICATION THROUGH TAU 120. NUMERICAL TRACK GUIDANCE COMES INTO
BETTER AGREEMENT BEYOND TAU 72, WITH ALL MODELS AGREEING ON THE
TRACK AND VERY LITTLE CROSS-TRACK DIFFERENCES, LENDING HIGH
CONFIDENCE IN THE JTWC FORECAST TRACK. HOWEVER, DUE TO THE HIGH
UNCERTAINTY IN THE EARLY PORTIONS OF THE FORECAST THERE IS OVERALL
LOW CONFIDENCE IN THE TOTALITY OF THE FORECAST TRACK.//
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