Tropical Storm NEOGURI Advisory Sat Jul 05

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 08W (NEOGURI)
WARNING NR 06//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 08W (NEOGURI), LOCATED APPROXIMATELY 207 NM
WEST OF ANDERSEN AFB, HAS TRACKED NORTHWESTWARD AT 13 KNOTS OVER THE
PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI)
DEPICTS A CONSOLIDATING LOW-LEVEL CIRCULATION CENTER (LLCC) WITH
TIGHTLY-CURVED BANDING WRAPPING INTO A PARTIALLY-EXPOSED CENTER. A
040727Z SSMIS IMAGE INDICATES DEEP CONVECTIVE BANDING PRIMARILY OVER
THE SOUTHERN SEMI-CIRCLE; HOWEVER, BANDING HAS IMPROVED
SIGNIFICANTLY OVER THE NORTH QUADRANT OVER THE PAST SIX HOURS AND
THERE IS A WELL-DEFINED MICROWAVE EYE FEATURE. THEREFORE, THERE IS
GOOD CONFIDENCE IN THE INITIAL POSITION AND RECENT TRACK MOTION. THE
INITIAL INTENSITY IS ASSESSED AT 55 KNOTS BASED ON THE IMPROVED
STRUCTURE AND A DVORAK INTENSITY ESTIMATE OF 55 KNOTS FROM PGTW. 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.
DYNAMIC MODEL GUIDANCE IS GOOD AGREEMENT WITH A 160 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. DYNAMIC MODEL GUIDANCE REMAINS IN GOOD AGREEMENT WITH A 175 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 16 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
DECRAESING SST.//
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