#389 Postby euro6208 » Thu Oct 25, 2018 10:52 pm 
			
			
			
			WDPN31 PGTW 260300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 31W (YUTU) WARNING NR 
19//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   SUPER TYPHOON (STY) 31W (YUTU), LOCATED APPROXIMATELY 903 NM 
SOUTHEAST OF KADENA AB, OKINAWA, JAPAN, HAS TRACKED WEST-
NORTHWESTWARD AT 11 KNOTS OVER THE PAST SIX HOURS. ANIMATED 
MULTISPECTRAL SATELLITE IMAGERY DEPICTS A CONSOLIDATING, SYMMETRIC 
EYEWALL SURROUNDING AN OBLONG EYE. ADDITIONALLY, A 260033Z AMSU 
89GHZ IMAGE REVEALS A 40NM MICROWAVE EYE FEATURE, THEREFORE, THERE 
IS GOOD CONFIDENCE IN THE INITIAL POSITION. HOWEVER, RECENT ANIMATED 
SATELLITE IMAGERY CONTINUES TO INDICATE TROCHOIDAL TRACK MOTION. 
UPPER-LEVEL ANALYSIS INDICATES A FAVORABLE ENVIRONMENT WITH LOW (10 
TO 15 KNOTS) EASTERLY VERTICAL WIND SHEAR AND ROBUST OUTFLOW WITH 
THE EXCEPTION OF THE EASTERN QUADRANT. THE INITIAL INTENSITY IS HELD 
AT SUPER TYPHOON STRENGTH (130 KNOTS) BASED ON A PGTW DVORAK CURRENT 
INTENSITY ESTIMATE OF 127 KNOTS, CONSISTENT WITH A 252137Z SATCON 
ESTIMATE OF 128 KNOTS. STY 31W IS TRACKING WEST-NORTHWESTWARD ALONG 
THE SOUTHWEST PERIPHERY OF A DEEP SUBTROPICAL RIDGE (STR) POSITIONED 
TO THE NORTHEAST WITH A BREAK IN THE STR LOCATED SOUTH OF HONSHU 
(NORTH OF THE SYSTEM) ASSOCIATED WITH A BROAD, WEAK MIDLATITUDE 
SHORTWAVE TROUGH.  
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. STY 31W IS FORECAST TO CONTINUE TRACKING WEST-NORTHWESTWARD 
TOWARD THE BREAK IN THE STR THROUGH TAU 36, HOWEVER, THE SYSTEM 
SHOULD GRADUALLY TURN MORE WESTWARD AFTER TAU 36 AS THE 
AFOREMENTIONED SHORTWAVE TROUGH PROPAGATES EASTWARD AND A BROAD 
MIDLATITUDE RIDGE TO THE NORTH ALLOWS THE STR TO RE-BUILD. EXCLUDING 
THE PRIMARY OUTLIERS, COAMPS-TC (CTCX) AND NAVGEM, DYNAMIC MODEL 
GUIDANCE IS IN BETTER AGREEMENT THROUGH TAU 72 WITH A 170NM SPREAD 
IN SOLUTIONS AT TAU 72. STY 31W IS EXPECTED TO MAINTAIN NEAR-STY 
STRENGTH THROUGH TAU 12 AS THE EYEWALL RE-STRENGTHENS AND THE EYE 
CONTRACTS. HOWEVER, AFTER TAU 12, THE SYSTEM SHOULD GRADUALLY WEAKEN 
AS VERTICAL WIND SHEAR INCREASES TO MODERATE LEVELS.     
   C. BEYOND TAU 72, THERE IS INCREASING UNCERTAINTY IN THE FORECAST 
TRACK WITH TWO DISTINCT CLUSTERS OF MODEL GUIDANCE. ECMWF, EEMN, 
UKMET, JGSM, AFUM, GFS, AEMN AND HWRF INDICATE A WEST-SOUTHWESTWARD 
(OVER LUZON) TO WEST-NORTHWESTWARD (TOWARD THE LUZON STRAIT) TRACK. 
NAVGEM AND COAMPS-TC (CTCX) CONTINUE TO INDICATE AN UNLIKELY RECURVE 
SCENARIO. BASED ON ANALYSIS OF MODEL FIELDS FROM BOTH CLUSTERS, THE 
RE-CURVE SCENARIO IS ASSESSED AS UNLIKELY DUE TO A LACK OF A DEEP 
MIDLATITUDE SHORTWAVE TROUGH AND THE PRESENCE OF A LOW-LEVEL RIDGE 
FORECAST TO BUILD OVER THE EAST CHINA SEA. THE JTWC FORECAST TRACK 
FAVORS A MORE WESTWARD TRACK WITH A DECREASE IN TRACK SPEEDS 
ASSOCIATED WITH A BREAK IN THE STR AND INCREASING NORTHEASTERLY LOW-
LEVEL FLOW FORECAST TO DEVELOP EAST OF TAIWAN. BASED ON THE 
BIFURCATION IN THE DYNAMIC MODELS AND LARGE OVERALL SPREAD, THERE IS 
LOW CONFIDENCE IN THIS PORTION OF THE JTWC FORECAST TRACK.//
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