Tropical Storm HAGIBIS Advisory 10月8日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 20W (HAGIBIS) WARNING NR
011//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   SUPER TYPHOON (STY) 20W (HAGIBIS), LOCATED APPROXIMATELY 168 NM
NORTH OF ANDERSEN AFB, GUAM, HAS TRACKED WEST-NORTHWESTWARD AT 17
KNOTS (KTS) OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED
SATELLITE IMAGERY (EIR) DEPICTS STY 20W AS A HIGHLY SYMMETRIC SYSTEM
WITH SPIRAL CONVECTIVE BANDS WRAPPING TIGHTLY INTO A SMALL, 6 NM
DIAMETER EYE SURROUNDED BY A WELL-DEFINED EYEWALL. THERE IS HIGH
CONFIDENCE IN THE INITIAL POSITION. THE INITIAL INTENSITY IS SET AT
140 KTS, SUPPORTED BY DVORAK CURRENT INTENSITY (CI) ESTIMATES OF
T7.0/140 KTS FROM PGTW AND RJTD, BOTH OF WHICH ARE CORROBORATED BY
THE CIMSS ADVANCED DVORAK TECHNIQUE (ADT) AND SATCON ESTIMATES.
THERE ARE INDICATIONS THAT THE SYSTEM HAS BEEN UNDERGOING AN EYEWALL
REPLACEMENT CYCLE (ERC) SINCE THE PREVIOUS WARNING, RESULTING IN A
STEADY-STATE INTENSITY OF 140 KTS. UPPER-LEVEL ANALYSIS SHOWS STRONG
RADIAL OUTFLOW WITH ENHANCED OUTFLOW EQUATORWARD AND EASTWARD. WITH
LOW (05-10 KTS) VERTICAL WIND SHEAR (VWS) AND HIGH (30-31 CELSIUS)
SEA SURFACE TEMPERATURES (SST), STY 20W CONTINUES TO TRACK THROUGH A
HIGHLY FAVORABLE ENVIRONMENT, WITH SOME FURTHER INTENSIFICATION
POSSIBLE AFTER THE COMPLETION OF THE CURRENT ERC. A SUBTROPICAL
RIDGE (STR) TO THE NORTH IS THE PRIMARY STEERING INFLUENCE AS THE
SYSTEM TRACKS WEST-NORTHWESTWARD ALONG ITS SOUTHERN PERIPHERY.
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM
THE LAST PROGNOSTIC REASONING MESSAGE.
   B. THROUGH TAU 72, STY 20W WILL CONTINUE TO TRACK NORTHWESTWARD
ALONG THE SOUTHWESTERN PERIPHERY OF THE AFOREMENTIONED STR. THE
FAVORABLE ENVIRONMENT (LOW VWS, HIGH SST, AND EXCELLENT UPPER-LEVEL
OUTFLOW) IS EXPECTED TO PERSIST THROUGH THE SHORT-TERM FORECAST
PERIOD, ALLOWING FOR INTENSIFICATION TO A PEAK OF 145 KTS BY TAU 12.
AFTERWARDS, THE INTENSITY WILL SLOWLY BEGIN TO WEAKEN AS THE
SYSTEM?S OUTFLOW BEGINS TO BE DISRUPTED TO THE NORTHWEST. NUMERICAL
MODELS ARE IN TIGHT AGREEMENT, SLOWLY INCREASING TO A CROSS-TRACK
SPREAD OF 140 NM BY TAU 72, LENDING HIGH CONFIDENCE IN THIS PORTION
OF THE JTWC TRACK FORECAST.
   C. IN THE EXTENDED FORECAST, A SHORTWAVE TROUGH OVER JAPAN IS
EXPECTED TO DEEPEN, ERODING THE STR AND ALLOWING STY 20W TO TURN
NORTHWARD AS IT ROUNDS THE STR AXIS. AROUND TAU 96, THE SYSTEM WILL
BEGIN TO RECURVE, TRACKING NORTHEASTWARD THROUGH THE REMAINDER OF
THE FORECAST PERIOD. AS IT DOES SO, THE SYSTEM WILL SLOWLY WEAKEN IN
RESPONSE TO INCREASE VWS ASSOCIATED WITH THE APPROACHING TROUGH,
WHICH WILL OFFSET THE OTHERWISE FAVORABLE ENVIRONMENT. THE NUMERICAL
MODELS HAVE A LOW (90 NM) CROSS-TRACK SPREAD AT TAU 120. HOWEVER,
THE TIMING OF THE RECURVATURE RESULTS IN UNCERTAINTIES WITH THE
FORWARD MOTION OF THE SYSTEM, LENDING LOW CONFIDENCE IN THE EXTENDED
PORTION OF THE JTWC FORECAST.//
NNNN
NNNN