Tropical Storm NEOGURI Advisory Fri Jul 04

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 08W (NEOGURI)
WARNING NR 07//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 08W (NEOGURI), LOCATED APPROXIMATELY 1044 NM
SOUTHEAST OF KADENA AB, HAS TRACKED WEST-NORTHWESTWARD AT 14 KNOTS
OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE
IMAGERY DEPICTS A CONSOLIDATING LOW-LEVEL CIRCULATION CENTER (LLCC)
WITH TIGHTLY-CURVED BANDING WRAPPING INTO A WELL-DEFINED CENTER. A
041218Z METOP-A IMAGE SHOWS A DEVELOPING EYEWALL, BROKEN OVER THE
WESTERN QUADRANT, WITH A DEEP CONVECTIVE BAND OVER THE SOUTHERN SEMI-
CIRCLE WRAPPING INTO THE NORTHEAST QUADRANT OF THE LLCC. A 041130Z
ASCAT IMAGE SHOWS AN EXTENSIVE BAND OF 50 KNOT WINDS OVER THE
EASTERN SEMI-CIRCLE WITH SOME ISOLATED 55 KNOT VECTORS. OVERALL,
THERE IS GOOD CONFIDENCE IN THE INITIAL POSITION AND RECENT TRACK
MOTION. THE INITIAL INTENSITY IS ASSESSED AT 60 KNOTS BASED ON THE
IMPROVED STRUCTURE AND DVORAK INTENSITY ESTIMATES RANGING FROM 55 TO
65 KNOTS. TS 08W IS TRACKING ALONG THE SOUTHERN PERIPHERY OF A DEEP
SUBTROPICAL RIDGE (STR) ENTRENCHED TO THE NORTH.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TS 08W IS FORECAST TO TRACK GENERALLY NORTHWESTWARD THROUGH
TAU 72 AS THE SYSTEM TRACKS ALONG THE SOUTHWEST PERIPHERY OF THE STR.
WITH THE EXCEPTION OF GFDN, DYNAMIC MODEL GUIDANCE IS GOOD AGREEMENT
WITH A 135 NM SPREAD IN SOLUTIONS AT TAU 72. FORECAST UNCERTAINTY IS
MAINLY ATTRIBUTED TO MINOR DIFFERENCES IN HOW THE STR IS DEPICTED.
BASED ON THE 04/00Z 500 MB ANALYSIS, THE STR HAS MAINTAINED STRENGTH
OVER THE PAST 24 HOURS AND IS ORIENTED EAST-WEST, EXTENDING AS FAR
WEST AS TAIWAN. TS 08W IS FORECAST TO RAPIDLY INTENSIFY THROUGH THE
NEXT 48 HOURS DUE TO FAVORABLE UPPER-LEVEL CONDITIONS AND VERY
FAVORABLE SEA SURFACE TEMPERATURES (SST) AND HIGH OCEAN HEAT CONTENT
VALUES.
   C. IN THE EXTENDED TAUS, TS 08W IS FORECAST TO TRACK NORTHWARD
ALONG THE WESTERN PERIPHERY OF A POLEWARD ORIENTED STR. THE SYSTEM
IS NOT EXPECTED TO ACCELERATE AND BEGIN EXTRA-TROPICAL TRANSITION
(ETT) UNTIL AFTER TAU 120 WHEN THE SYSTEM FIRST BEGINS TO ENCOUNTER
INCREASING MIDLATITUDE WESTERLIES NEAR WESTERN JAPAN AND THE EAST
SEA. WITH THE EXCEPTION OF GFDN, DYNAMIC MODEL GUIDANCE REMAINS IN
GOOD AGREEMENT WITH A 145 NM SPREAD IN SOLUTIONS AT TAU 96, NEAR
OKINAWA. FORECAST TRACK UNCERTAINTY REMAINS WITH ECMWF INDICATING A
MORE WESTWARD TRACK AND RE-CURVE JUST WEST OF OKINAWA WHILE THE
REMAINDER OF THE GUIDANCE RE-CURVES THE SYSTEM OVER OR TO THE EAST
OF OKINAWA. THE DYNAMIC MODELS ALSO INDICATE DIFFERENT TRACK SPEEDS
BUT, WITH THE EXCEPTION OF COAMPS-TC, THE MODELS SUPPORT MODEST
TRACK SPEEDS 09 TO 15 KNOTS, TYPICAL OF A POLEWARD FLOW PATTERN. DUE
TO THE TIGHT MODEL AGREEMENT, THERE IS HIGH CONFIDENCE IN THE JTWC
FORECAST TRACK, WHICH IS POSITIONED CLOSE TO THE MULTI-MODEL
CONSENSUS BUT FASTER TO OFFSET THE SLOW-TRACKING GFDN GUIDANCE. IT
IS IMPORTANT TO NOTE THAT THIS IS NOT THE TYPICAL RE-CURVE PATTERN,
THEREFORE, THERE IS NO NEED TO ADJUST FOR HISTORICAL MODEL BIAS
(MODELS TOO SLOW AND WEST OF THE ACTUAL TRACK), WHICH IS USED NORTH
OF THE RIDGE AXIS IN A RE-CURVE SCENARIO. IN FACT, AS MENTIONED
EARLIER, THE SYSTEM DOES NOT TRACK POLEWARD OF THE STR AXIS UNTIL
AFTER TAU 120 AT WHICH POINT IT IS EXPECTED TO RE-CURVE SHARPLY
EASTWARD AND TO UNDERGO ETT. TS 08W IS FORECAST TO WEAKEN SLIGHTLY
AFTER TAU 84 WITH MORE SIGNIFICANT WEAKENING TREND AFTER TAU 96 DUE
TO INCREASING LAND INTERACTION AND DECREASING SST.//
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