Tropical Storm KALMAEGI Advisory 11月15日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 27W (KALMAEGI)
WARNING NR 009//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION 27W (KALMAEGI), LOCATED APPROXIMATELY 303 NM
EAST-NORTHEAST OF MANILA, PHILIPPINES, HAS TRACKED NORTHWESTWARD AT
09 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR)
SATELLITE IMAGERY SHOWS A LARGE AREA OF DISORGANIZED, FLARING DEEP
CONVECTION SHEARED TO THE NORTH, WITH AN EXTREMELY ELONGATED AND
RAGGED LOW LEVEL CENTER (LLC). A 141735Z AMSR-2 89GHZ IMAGE
INDICATES AN AREA OF BROAD, FAINT TURNING WITH DEEP CONVECTION TO
THE NORTHEAST; HOWEVER, THE LLC IS OBSCURED IN THE EIR LOOP, AND
THERE IS EXTREMELY LOW CONFIDENCE IN THE INITIAL POSITION. THE
INITIAL INTENSITY REMAINS ASSESSED AT 30 KNOTS BASED ON THE
CONTINUING SHEAR AND DISORGANIZATION AND A PGTW DVORAK CURRENT
INTENSITY ESTIMATE OF T2.0 (30 KTS). ENVIRONMENTAL ANALYSIS REVEALS
A FAVORABLE ENVIRONMENT WITH STRONG POLEWARD AND WESTWARD DIFFLUENCE
ALOFT, WARM SST (29C) AND HIGH OCEAN HEAT CONTENT VALUES. TD 27W IS
TRACKING ALONG THE SOUTHWESTERN PERIPHERY OF A SUBTROPICAL STEERING
RIDGE SITUATED TO THE NORTHEAST.
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM
THE PREVIOUS PROGNOSTIC REASONING MESSAGE. HOWEVER, THE SHORT-TERM
FORECAST HAS BEEN ADJUSTED SIGNIFICANTLY TO REFLECT A WEAK STEERING
ENVIRONMENT AND SLOW, MEANDERING MOTION THROUGH TAU 48. PREVIOUSLY,
IT WAS STATED THAT A SUBTROPICAL RIDGE TO THE NORTHEAST WAS THE
DOMINANT STEERING FEATURE IN THE NEAR-TERM. HOWEVER, THE SYSTEM IS
STILL TOO WEAK TO FEEL THE DEEP-LAYERED FLOW, AND IS RESPONDING
INSTEAD TO THE LOWER-LEVEL NORTHEASTERLY COLD SURGE AND A COL IN
700MB RIDGING TO ITS NORTH.
   B. TD 27W WILL MEANDER WESTWARD IN A WEAK STEERING ENVIRONMENT,
AS A PASSING MIDLATITUDE TROUGH TO THE NORTH HAS CAUSED A BREAK IN
THE LOWER LEVEL SUBTROPICAL STEERING RIDGE. ECMWF AND GFS HAVE
DRAMATICALLY SHIFTED THEIR TRACKS SOUTHWARD AND MUCH SLOWER IN ALONG-
TRACK SPEED IN THE NEAR-TERM, AND THE JTWC FORECAST TRACK HAS
SHIFTED SIGNIFICANTLY BEHIND AND SOUTH OF THE PREVIOUS TRACK TO
REFLECT THIS. AFTER TAU 48, RIDGING IS EXPECTED TO BUILD TO THE
NORTH OF THE SYSTEM, STEERING IT WEST-NORTHWESTWARD TOWARD LUZON.
THE MAJORITY OF NUMERICAL MODEL GUIDANCE INDICATES A TRACK OVER
LUZON. HOWEVER, GIVEN THE DISORGANIZATION OF THIS SYSTEM, EXACTLY
WHAT VORTEX CENTER THE MODELS ARE TRACKING IS DEBATABLE.
ADDITIONALLY, GIVEN THE STRONG NORTHEASTERLY SURFACE SURGE, WHICH 34-
KT WINDS ARE ATTRIBUTABLE TO THE SYSTEM AND WHICH ARE RELATED TO THE
TROPICAL CYCLONE IS DIFFICULT TO DEFINE. WIND RADII HAVE BEEN SET
LARGER ON THE NORTHEASTERN SIDE DUE TO THE SURGE FLOW. BASED ON
UNCERTAINTY IN THE CURRENT POSITION AND THE DRAMATIC CHANGES IN
MODEL FORECAST TRACKS BETWEEN RUNS, THERE IS LOW CONFIDENCE IN THIS
PORTION OF THE FORECAST TRACK. IN THE NEAR TERM, 27W WILL SLOWLY
INTENSIFY TO A PEAK OF 50 KTS AT TAU 48 DUE TO ENHANCED POLEWARD
OUTFLOW AND THE SYSTEM TRACKING SLOWLY OVER HIGH OCEAN HEAT CONTENT
WATER. HOWEVER, TOTAL INTENSIFICATION WILL BE LIMITED BY HIGH VWS.
   C. AFTER TAU 72, TD 27W IS EXPECTED TO CONTINUE TRACKING WESTWARD
ACROSS LUZON. AS IT WEAKENS, IT WILL BEGIN TO RESPOND TO SURFACE
NORTHEASTERLY SURGE AND TRACK SOUTHWESTWARD INTO THE SOUTH CHINA
SEA. PASSAGE OVER THE MOUNTAINOUS TERRAIN OF LUZON, REDUCED
DIVERGENCE ALOFT AS RIDGING BUILDS TO ITS NORTH, AND AS COLD, DRY
AIR ENTRAINMENT WILL RESULT IN STEADY WEAKENING. THIS PORTION OF THE
FORECAST TRACK IS SIMILAR TO PREVIOUS FORECAST TRACKS. THE JTWC
FORECAST INTENSITY IS BELOW THE MULTIMODEL INTENSITY GUIDANCE,
BECAUSE STATISTICAL MODELS ARE NOT ACCURATELY REFLECTING THE HIGH
VERTICAL WIND SHEAR IN THE AREA, WHICH WILL CONTINUE TO LIMIT
INTENSIFICATION. MODEL SPREAD PERSISTS INTO THE EXTENDED FORECAST
PERIOD, LENDING LOW CONFIDENCE TO THE EXTENDED PORTION OF THE
FORECAST TRACK.//
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