Tropical Storm NEOGURI Advisory Fri Oct 18

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 21W (NEOGURI) WARNING
NR 007//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 21W (NEOGURI), LOCATED APPROXIMATELY 408 NM
SOUTH-SOUTHEAST OF KADENA AB, HAS TRACKED NORTH-NORTHWESTWARD AT 06
KNOTS (KTS) OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY REVEALS DEEP CONVECTION OBSCURING A LOW LEVEL CIRCULATION
CENTER. THE POSITION IS PLACED WITH GOOD CONFIDENCE BASED ON AN
180050Z METOP-B ASCAT PASS AND AN 180048Z AMSU 89GHZ MICROWAVE IMAGE.
THE INITIAL INTENSITY OF 45 KTS IS SET WITH GOOD CONFIDENCE BASED ON
THE AFOREMENTIONED ASCAT PASS. THIS INTENSITY IS SLIGHTLY BELOW THE
180110Z ADVANCED DVORAK TECHNIQUE ESTIMATE OF 51 KTS. THE ENVIRONMENT
IS FAVORABLE WITH LOW (10-15 KTS) VERTICAL WIND SHEAR (VWS), GOOD
POLEWARD OUTFLOW, AND WARM (28-29 CELSIUS) SEA SURFACE TEMPERATURE
(SST). TS 21W IS TRACKING SLOWLY NORTHWESTWARD AROUND THE SOUTHWEST
PERIPHERY OF A SUBTROPICAL RIDGE (STR) TO THE NORTHEAST.
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM
THE LAST PROGNOSTIC REASONING MESSAGE.
   B. IN THE NEAR TERM, TS 21W IS EXPECTED TO MAINTAIN A
NORTHWESTERLY TRACK UNTIL TAU 48 WHEN IT ROUNDS THE STR AXIS. THERE
IS SIGNIFICANT UNCERTAINTY IN THE TIMING AND STRENGTH OF THE STR. DUE
TO THIS UNCERTAINTY, THERE IS POOR CONFIDENCE IN TRACK GUIDANCE AS
THERE IS A 320 NM SPREAD BETWEEN TRACK MEMBERS BY TAU 72. UNTIL THIS
POINT IN THE FORECAST, THE UPPER LEVEL ENVIRONMENT HAS LIMITED THE
INTENSIFICATION OF TS 21W. HOWEVER, WITH THE APPROACHING TROUGH TO
THE NORTHWEST, THE  POLEWARD OUTFLOW MAY STRENGTHEN AND CAUSE A
SLIGHT INTENSIFICATION TO 50 KTS BY TAU 24. TS 21W IS EXPECTED TO
CROSS THE STR AXIS BY TAU 72 AND BEGIN RECURVING TO THE NORTHEAST.
OVERALL, GLOBAL MODELS HAVE MAINTAINED THE RECURVE SCENARIO, WITH
EXCEPTION OF NAVGEM AND ECMWF . THE JTWC TRACK FORECAST IS PLACED
NEAR THE CONSENSUS. DUE TO THE AFOREMENTIONED FACTORS, THERE IS
OVERALL LOW TRACK AND INTENSITY CONFIDENCE IN THIS PORTION OF THE
FORECAST.
   C. BEYOND TAU 72, TS 21W IS EXPECTED TO RECURVE AS THE APPROACHING
TROUGH WEAKENS THE STR AND TS 21W ENCOUNTERS SOUTHWESTERLY FLOW. TS
21W IS CURRENTLY EXPECTED TO ENCOUNTER INCREASED SHEAR WHICH WILL
LIKELY WEAKEN TS 21W ALONG ITS NORTHEAST TRACK. WITH SPREAD EXCEEDING
730 NM BY TAU 120, THERE IS LOW CONFIDENCE IN THE EXTENDED PORTION OF
THE JTWC TRACK FORECAST.//
NNNN
NNNN