Tropical Storm NALGAE Advisory 10月28日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 26W (NALGAE) WARNING NR
004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
   INITIAL POSITION: 12.1N 129.6E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 524 NM EAST-SOUTHEAST OF MANILA,
PHILIPPINES
   MOVEMENT PAST 6 HOURS: WESTWARD AT 05 KTS
   SIGNIFICANT WAVE HEIGHT: 17 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED IMAGERY (EIR) DEPICTS A LARGE AND
DISORGANIZED SYSTEM WITH A DIPOLE OF PULSATING DEEP CONVECTION
EMBEDDED WITHIN THE BROAD ENVELOPE OF CIRCULATION. THE EASTERN
TOWER, CLOSER TO THE CURRENT BEST TRACK POSITION, HAD BEEN BUILDING
AND INSPIRING HOPE THAT THE LOW LEVEL CIRCULATION CENTER (LLCC) MIGHT
FINALLY CONSOLIDATE, BUT IT HAS SINCE COLLAPSED AND DEEP CONVECTION
IS NOW CONCENTRATING BACK AROUND THE WESTERN SIDE. A POINT SOURCE
OVER THE SOUTHERN EXTENT IS FUELING ROBUST EQUATORWARD OUTFLOW, BUT
INDUCED TROUGHING AND CONVERGENCE TO THE NORTH IS HAMPERING
DEVELOPMENT OF A VERTICALLY STACKED VORTEX, AND FURTHER SHOWCASING
THE DICHOTOMY OF FACTORS OF THIS COMPLEX MONSOON DEPRESSION (MD).
DETERMINATION OF THE LLCC POSITION HAS BEEN COMPOUNDED BY A LACK OF
OCEAN SURFACE WIND VECTOR DATA (OSWV) OVER THE PAST TWELVE HOURS,
HOWEVER, A 271914Z SSMIS 91 GHZ IMAGE SUGGESTS A BROAD CENTER NEAR
THE LATEST PGTW AND RJTD FIXES. THE INITIAL POSITION WAS BASED ON
THESE FIXES WITH LOW CONFIDENCE. THE INITIAL INTENSITY WAS RAISED
TO 40 KNOTS, BUT THIS ASSESSMENT IS BASED ON THE STRONGER WINDS
DISPLACED WELL TO THE SOUTH OF THE CENTER, CONSISTENT WITH MD
STRUCTURE.
INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK, NO OSWV OR OTHER
WIND DATA TO SUPPORT
CURRENT STEERING MECHANISM: LOW- TO MID-LEVEL SUBTROPICAL RIDGE
(STR) POSITIONED TO THE NORTH.
AGENCY DVORAK AND AUTOMATED FIXES:
   PGTW: T2.0 - 30 KTS
   RJTD: T2.0 - 30 KTS
   KNES: T2.5 - 35 KTS
   CIMSS ADT: 35 KTS AT 271740Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG EQUATORWARD
ANALYSIS CONFIDENCE:
   INITIAL POSITION: LOW
   INITIAL INTENSITY: LOW
   INITIAL WIND RADII: LOW
3. FORECAST REASONING.
SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.
FORECAST DISCUSSION: TS 26W IS STRUGGLING TO CONSOLIDATE DUE TO A
MARGINALLY FAVORABLE ENVIRONMENT, HOWEVER, THE TUTT IS FORECAST TO
WEAKEN WITH EXPANDING POLEWARD OUTFLOW INTO THE WESTERLIES TO THE
NORTH DEVELOPING WITHIN THE NEXT 12 TO 24 HOURS. THIS SHOULD ALLOW
THE SYSTEM TO CONSOLIDATE AND INTENSIFY AT A FASTER RATE TO A PEAK OF
70 KNOTS BY TAU 36, PRIOR TO LANDFALL OVER EASTERN LUZON. TS 26W
WILL WEAKEN SIGNIFICANTLY AS IT PASSES OVER THE PHILIPPINES. A LARGE
SUBTROPICAL RIDGE IS EXPECTED TO BUILD OVER THE EASTERN PHILIPPINE
SEA, ASSISTING IN A POLEWARD TURN, WHILE MODELS ARE INCREASINGLY
INDICATING UPPER LEVEL FLOW WILL BE ZONAL, WHICH WOULD LESSEN THE
LIKELIHOOD OF A CLASSICAL TROUGH INDUCED RECURVATURE SCENARIO. THE
EXTENDED FORECAST WAS SLOWED TAKING INTO ACCOUNT THE TRENDING
GUIDANCE. SLIGHT INTENSIFICATION IS FORECAST AFTER NALGAE ENTERS THE
SOUTH CHINA SEA, BUT THIS SHOULD BE SHORT LIVED AS 26W ENCOUNTERS A
MUCH
MORE UNFAVORABLE ENVIRONMENT NEAR TAIWAN.
MODEL DISCUSSION: DETERMINISTIC MULTI-MODEL GUIDANCE IS IN FAIR
AGREEMENT THROUGH TAU 48, HOWEVER, AFTER THAT TIME THERE IS A
BIFURCATION IN THE GUIDANCE. THE ECMWF MODEL CONTINUES ON A
NORTHWESTWARD TRACK. SIXTY PERCENT OF THE ECMWF ENSEMBLE SOLUTIONS
ALSO ALIGN WITH THE WESTWARD RUNNING SOLUTION AND DISSIPATION IN THE
SOUTH CHINA SEA, WHEREAS 40 PERCENT OF MEMBERS RECURVE TOWARDS
TAIWAN. GFS ENSEMBLE SPREAD ROUGHLY FOLLOWS THIS SPLIT. INTENSITY
GUIDANCE CONTINUES TO HOVER AROUND A PEAK INTENSITY OF 70 KNOTS, AND
A NUMBER OF RAPID INTENSITY GUIDANCE PRODUCTS WERE TRIGGERED.
HOWEVER, SUCH INTENSIFICATION IS UNLIKELY TO OCCUR UNTIL THE LLCC
FINALLY CONSOLIDATES. THE PROXIMITY TO LANDFALL TIMING SHOULD LIMIT
THE OVERALL PEAK INTENSITY AS WELL. DUE TO THE LARGE SPREAD IN
DETERMINISTIC AND PROBABILISTIC GUIDANCE IN THE EXTENDED PERIOD AND
POSSIBLE INTERACTION WITH THE NORTHEAST SURGE EVENT, THERE IS LOW
CONFIDENCE IN THE 72-120 HOUR JTWC FORECAST TRACK AND INTENSITY
FORECAST.
FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   TRACK 72-120 HR: LOW
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: LOW//
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