Tropical Storm HAIKUI Advisory Fri Aug 03

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 12W (TWELVE)
WARNING NR 02//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION 12W (TWELVE), LOCATED APPROXIMATELY 740 NM
EAST OF KADENA AB, JAPAN, HAS TRACKED WEST-NORTHWESTWARD AT 07 KNOTS
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY
INDICATES IMPROVED CONVECTIVE BANDING WRAPPING INTO THE NORTH
QUADRANT WITH INCREASED DEEP CONVECTION OVER THE SOUTHWEST QUADRANT.
ANIMATED WATER VAPOR IMAGERY INDICATES THAT THE TUTT CELL, WHICH HAD
BEEN INHIBITING CONVECTION OVER THE LOW-LEVEL CIRCULATION CENTER
(LLCC) HAS SLOWLY TRACKED WEST AND IS NOW LOCATED ABOUT 150-200 NM
WEST OF THE CENTER. CONSEQUENTLY, POLEWARD OUTFLOW AND CONVECTIVE
ORGANIZATION HAVE IMPROVED SLIGHTLY. DVORAK ESTIMATES FROM PGTW AND
RJTD, HOWEVER, HAVE REMAINED STEADY AT 25 KNOTS. THE INITIAL
INTENSITY IS HEDGED HIGHER THAN THE DVORAK ESTIMATES BASED ON IWO-TO
OBSERVATION (ABOUT 60NM NORTH OF THE CENTER), WHICH SHOW SUSTAINED
EAST-SOUTHEASTERLY WINDS OF 25-32 KNOTS AND SLP OF 990 MB (AND A
NOTEWORTHY 11MB 24-HOUR SLP DECREASE). ADDITIONALLY, UPPER AIR DATA
FROM CHICHI-JIMA SHOWS 40-45 KNOT GRADIENT WINDS. THIS DATA CLEARLY
SUPPORTS A LARGE, DEVELOPING SYSTEM. THERE IS MODERATE CONFIDENCE IN
THE CURRENT POSITION DUE TO THE ELONGATED NATURE OF THE LLCC AND THE
LACK OF DEEP CONVECTIVE BANDING NEAR THE CENTER.
3. FORECAST REASONING.
   A. NO CHANGE IN THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TD 12W IS FORECAST TO TRACK WESTWARD THROUGH TAU 72 UNDER THE
STEERING INFLUENCE OF A DEEP SUBTROPICAL RIDGE (STR) POSITIONED
SOUTH OF JAPAN. DYNAMIC MODEL GUIDANCE (NOGAPS, UKMO, ECMWF, GFDN,
GFS, JGSM) IS IN TIGHT AGREEMENT WITH A 80NM SPREAD AT TAU 72,
CENTERED JUST NORTH OF OKINAWA. THEREFORE, THERE IS HIGH CONFIDENCE
IN THE FORECAST TRACK THROUGH TAU 72. DUE TO THE BROAD NATURE OF THE
LLCC AND INITIAL POSITIONAL UNCERTAINTY, THERE MAY BE SMALL TRACK
SHIFTS UNTIL THE LLCC CONSOLIDATES. TD 12W IS EXPECTED TO INTENSIFY
SLOWLY THROUGH TAU 24-36 BUT SHOULD INTENSIFY RAPIDLY AFTER TAU 36
AS POLEWARD OUTFLOW IMPROVES AND THE TUTT CELL SHIFTS WEST OF THE
SYSTEM.
   C. THERE IS INCREASING UNCERTAINTY AFTER TAU 72 DUE TO A MAJOR
CHANGE IN THE SYNOPTIC PATTERN FORECAST TO EVOLVE AFTER TAU 48 BY
ALL THE MAJOR MODELS. A DEEP MIDLATITUDE SHORT-WAVE TROUGH IS
FORECAST TO DEEPEN OVER EASTERN ASIA AND DIG SOUTHWARD INTO THE EAST
CHINA SEA BY TAU 96. THIS WILL EFFECTIVELY PROVIDE A BLOCK TO
CONTINUED WESTWARD MOVEMENT AND PRODUCE A QUASI-STATIONARY PHASE
NORTHWEST OF OKINAWA THAT COULD PERSIST FOR 1-2 DAYS. THE MAJOR
DIFFERENCE IN THE DYNAMIC MODELS IS THE ORIENTATION AND STRENGTH OF
THIS DEEP SHORT-WAVE TROUGH AND, AS A RESULT, THE MODEL TRACKERS
SHOW A VARIETY OF POLEWARD TURN POINTS. NOGAPS SHOWS THE EARLIEST
TURN WITH A NORTHWARD TRACK TOWARD SHIKOKU AND ECMWF SHOWS THE
LATEST TURN, WEST OF KADENA, TOWARD SOUTH KOREA. THE OFFICIAL JTWC
FORECAST FAVORS THE ECMWF SOLUTION DUE TO PROBLEMS NOTED IN THE
NOGAPS' RAPID WEAKENING OF THE STR OVER JAPAN. TD IS EXPECTED TO
RAPIDLY INTENSIFY TO A PEAK INTENSITY OF 110 KNOTS BY TAU 120 UNDER
FAVORABLE CONDITIONS AND IMPROVED POLEWARD OUTFLOW. THERE IS LOW
CONFIDENCE IN THE EXTENDED TRACK FORECAST.//
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