Tropical Storm HAIKUI Advisory Thu Aug 02

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 12W (TWELVE)
WARNING NR 01//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION 12W (TWELVE), LOCATED APPROXIMATELY 70 NM
SOUTH-SOUTHEAST OF IWO-TO, JAPAN, HAS TRACKED WESTWARD AT 07 KNOTS
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY
(MSI) DEPICTS ONLY FLARING DEEP CONVECTION OVER A CONSOLIDATING LOW-
LEVEL CIRCULATION CENTER (LLCC); HOWEVER, THERE IS STRONG EVIDENCE
SUPPORTING THE CURRENT INTENSITY ASSESSMENT OF 30 KNOTS. A 022023Z
SSMIS 37 GHZ IMAGE DEPICTS FORMATIVE SHALLOW CONVECTIVE BANDING
WRAPPING INTO A ELONGATED LLCC, POSITIONED JUST SOUTH OF IWO-TO.
SURFACE OBSERVATIONS FROM IWO-TO, 70 NM NNE OF THE CENTER INDICATE
SUSTAINED WINDS OF 25 TO 30 KNOTS AND SLP NEAR 992 MB (AND A
NOTEWORTHY 10MB 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. THE INITIAL INTENSITY OF 30
KNOTS IS BASED ON THE IWO-TO SURFACE OBSERVATIONS AS WELL AS SHIP
OBSERVATIONS; THE DVORAK ESTIMATES HAVE REMAINED LOW AT 25 KNOTS DUE
TO THE LACK OF STRONG CENTRAL DEEP CONVECTION AT THIS TIME. ANIMATED
WATER VAPOR IMAGERY DEPICTS A SMALL TUTT CELL OVER THE LLCC, WHICH
IS SUPPRESSING CONVECTION. THIS TUTT CELL IS TRACKING SLOWLY
WESTWARD AND IS JUST BEGINNING TO PROVIDE A WEAK POLEWARD VENT.
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. THIS IS THE INITIAL PROGNOSTIC REASONING AND SETS THE FORECAST
PHILOSOPHY.
   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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