WDPN31 PGTW 201500
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 07W WARNING NR 09//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
A. OVER THE PAST 12 HOURS, TY 07W HAS INTENSIFIED SLIGHTLY
WHILE TRACKING STEADILY WEST-NORTHWESTWARD ALONG THE EQUATOR-
WARD PERIPHERY OF A SUBTROPICAL STEERING RIDGE TO THE NORTH.
METSAT DATA INDICATE THAT THE SYSTEM CENTER IS MOVING ACROSS
THE VISAYAN SEA, AMONG THE CENTRAL PHILIPPINE ISLANDS.
THE
TYPHOON HAS MAINTAINED A SYMMETRIC STRUCTURE AND DISPLAYS A
RAGID EYE FEATURE DESPITE INCREASING NORTHERLY VERTICAL WIND
SHEAR AND LAND INTERACTION. B. THE CURRENT STORM POSITION IS BASED ON SATELLITE FIXES
FROM PGTW AND RJTD. THE CURRENT INTENSITY ESTIMATE IS CONSIS-
TENT WITH DVORAK T-NUMBERS OF 4.5 AND 5.0 ASSOCIATED WITH THE
PGTW AND RJTD FIXES, RESPECTIVELY.
EXTENSIVE, WELL-DEVELOPED
DEEP CONVECTIVE BANDING EXTENDING ACROSS VERY WARM WATER AND
GOOD EQUATORWARD AND WESTWARD OUTFLOW ALOFT ARE ALLOWING TY 07W
TO MAINTAIN BOTH STRUCTURE AND INTENSITY. THE LOW TERRAIN OF
THE CENTRAL PHILIPPINE ISLANDS HAS PROVIDED LITTLE DISRUPTION
VIGOROUS LOW LEVEL INFLOW.
ADDITIONALLY, WELL-ESTABLISHED
CENTRAL CONVECTION IS APPARENTLY REDUCING THE IMPACT OF INCREAS-
ING UPPER LEVEL NORTHERLY FLOW ASSOCIATED WITH UPPER LEVEL
RIDGING TO THE NORTH OF THE TYPHOON. THE SUBTROPICAL RIDGE TO
THE NORTH OF TY 07W REMAINS AS THE PRIMARY STEERING INFLUENCE.
HOWEVER, ENHANCED LOW LEVEL SOUTHWESTERLY WINDS TO THE SOUTHEAST
OF THE TYPHOON, INDICATED BY A 202118Z QUIKSCAT PASS, AND RECENT
DEEP-LAYER WIND ANALYSIS SUGGEST THAT NEAR-EQUATORIAL RIDGING TO
THE SOUTHEAST HAS STRENGTHENED, AND MAY SOON PROVIDE A COMPETING
STEERING INFLUENCE.
3. FORECAST REASONING
A.
THE FORECAST REASONING HAS CHANGED SIGNIFICANTLY SINCE THE
PREVIOUS ISSUANCE OF THE PROGNOSTIC REASONING MESSAGE. THE FORE-
CAST TRACK HAS BEEN SHIFTED TO THE WEST IN RESPONSE TO A STRONGER
THAN PREVIOUSLY EXPECTED STEERING RIDGE TO THE NORTH. ADDITIONALLY,
FORECAST INTENSITIES HAVE BEEN REDUCED DUE TO THE ANTICIPATION OF
INCREASED LAND INTERACTION AND INCREASED NORTHERLY VERTICAL WIND
SHEAR INDUCED BY UPPER LEVEL RIDGING TO THE NORTH.
B. TY 07W IS EXPECTED TO CONTINUE TRACKING GENERALLY WESTWARD
TO NORTHWESTWARD OVER THE NEXT 24 HOURS UNDER THE STEERING INFLU-
ENCE OF THE SUBTROPICAL STEERING RIDGE TO THE NORTH. HOWEVER, THIS
RIDGE IS EXPECTED TO RETREAT WESTWARD OVER TIME, ALLOWING A DEVEL-
OPING NEAR-EQUATORIAL RIDGE TO THE SOUTHEAST OF THE TYPHOON TO
EXERT AN INCREASING INFLUENCE ON STORM MOTION. AS THIS NEAR-EQUA-
TORIAL RIDGE BUILDS, TY 07W WILL TURN POLEWARD. THIS POLEWARD TURN
IS NOW EXPECTED TO OCCUR TO THE WEST OF THE MERIDIONALLY-ORIENTED,
MOUNTAINOUS TERRAIN OF CENTRAL LUZON. TY 07W WILL MAINTAIN INTEN-
SITY OR INTENSIFY SLIGHLTY OVER THE NEXT 24 HOURS BEFORE MAKING
LANDFALL IN SOUTHERN LUZON.
PASSAGE OVER VERY WARM WATER AND
STRONG WESTWARD AND EQUATORWARD OUTFLOW WILL SUPPORT THIS SLIGHT
INTENSIFICATION. AFTER LANDFALL AROUND TAU 24, THE TYPHOON WILL
STEADILY WEAKEN TO TROPICAL STORM STRENGTH AS IT TRACKS ALONG
MOUTAINOUS CENTRAL LUZON. TY 07W WILL LIKELY ENTER A COMPETING
STEERING ENVIRONMENT BETWEEN THE SUBTROPICAL RIDGE TO THE NORTH
AND THE DEVELOPING NEAR-EQUATORIAL RIDGE TO THE SOUTHEAST AS IT
CROSSES LUZON. THUS, THE STORM IS LIKELY TO SLOW AND TURN
GRADUALLY POLEWARD AND PERHAPS EVEN NORTHEASTWARD BY TAU 72. THIS
ANTICIPATED TRACK WOULD LEAVE THE SYSTEM OVER LUZON FOR A
SIGNIFICANT PERIOD OF TIME. BECAUSE THE NUMERICAL MODELS DEPICT
A WEAKER SUBTROPICAL STEERING RIDGE TO THE NORTH AND STRONGER
NEAR-EQUATORIAL RIDGE TO THE SOUTHEAST THAN CURRENTLY ANALYZED,
THE FORECAST TRACK FORECAST HAS BEEN PLACED WELL TO THE WEST OF
THE NUMERICAL MODEL CONSENSUS.
C.
THE WEAKENED TS 07W IS EXPECTED TO INTENSIFY SLIGHTLY AS IT
REEMERGES OVER WATER TO THE NORTH OF LUZON IN THE EXTENDED FORE-
CAST PERIOD. IMPROVING POLEWARD OUTFLOW AND MODERATE OCEAN HEAT
CONTENT WILL SUPPORT THIS REINTENSIFICATION. HOWEVER, THE TROPICAL
SYSTEM WILL LIKELY CONTEND WITH INCREASING NORTHWESTERLY VERTICAL
WIND SHEAR AHEAD OF A DEVELOPING MID-LATITUDE TROUGH BY TAU 120,
WHICH SHOULD HALT THE INTENSIFICATION TREND.
FORECAST TEAM: ALPHA//
NNNN
Está claro que este ciclón está suponiendo todo un reto para los Meteorólogos responsables de su seguimiento y pronósticos... El mapa de trayectoria ha sido corregido ya un montón de veces pues el tifón se empeña en seguir desviándose hacia el oeste y, además, a pesar de que estar moviéndose sobre las Filipinas, se ha reintensificado en las últimas horas, a tenor del aspecto que ofrece en las últimas imágenes satelitales. De este modo, tras perder el ojo como comentaba en el mensaje anterior al mediodía, ahora vuelve a tomar forma, lo que sugiere una reorganización del tifón a pesar de interaccionar con tierra y un valor de cizalladura creciente. Puede que unas aguas muy cálidas estén siendo las responsables de la "dureza" de FENGSHEN :<<O Este fortalecimiento aparece en un aumento repentino del número DVORAK, que
sube a 5.5:
5.5 102 KTS 117 MPH 960 mb 941 mb 3 (97-113 KTS)
DATE/TIME LAT LON CLASSIFICATION STORM
20/2030 UTC 11.8N 123.0E T5.5/5.5 FENGSHEN