Tropical Storm HAIKUI Advisory jue, 09-11

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 30W (THIRTY)
WARNING NR 01//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION 30W (THIRTY), LOCATED APPROXIMATELY 226 NM
EAST-SOUTHEAST OF MANILA, PHILIPPINES, HAS TRACKED WEST-
NORTHWESTWARD AT 15 KNOTS OVER THE PAST SIX HOURS. ANIMATED
MULTISPECTRAL SATELLITE IMAGERY DEPICTS A RAPIDLY CONSOLIDATING
SYSTEM WITH BANDS OF DEEP CONVECTION WRAPPING INTO THE LOW LEVEL
CIRCULATION CENTER. THERE IS HIGH CONFIDENCE IN THE INITIAL POSITION
WHICH IS BASED ON A 082305Z 89GHZ AMSU-B IMAGE SHOWING A LOW
REFLECTIVITY CIRCULATION FEATURE WITH A BURST OF STRONG CENTRAL
CONVECTION. THE INITIAL INTENSITY IS ASSESSED AT 25 KNOTS AND IS
BASED ON AGENCY DVORAK ESTIMATES RANGING FROM T1.5 TO 2.0 (25 TO 30
KNOTS). A SURFACE OBSERVATION FROM CATARMAN, PHILIPPINES IS
REPORTING A STATION PRESSURE OF 1002 MB WHICH FURTHER SUPPORTS THE
INITIAL INTENSITY ESTIMATE. UPPER-LEVEL ANALYSIS SHOWS VERY LOW
VERTICAL WIND SHEAR AS AN ANTICYCLONE DEVELOPS OVER THE SYSTEM.
POLEWARD OUTFLOW IS ROBUST AS IT TAPS INTO THE MIDLATITUDE WESTERLY
JET, WHILE EQUATORWARD OUTFLOW EXHIBITING SUBSTANTIAL DIFFLUENCE.
CURRENTLY TD 30W IS TRACKING WEST-NORTHWEST ALONG THE SOUTHERN
BOUNDARY OF AN EAST-WEST ORIENTED SUBTROPICAL RIDGE (STR) LOCATED TO
THE NORTH
3. FORECAST REASONING.
   A. THIS IS THE INITIAL PROGNOSTIC REASONING AND SETS THE FORECAST
PHILOSOPHY.
   B. TD 30W WILL CONTINUE TRACKING WEST-NORTHWESTWARD OVER THE
FORECAST PERIOD ALONG THE SOUTHERN BOUNDARY OF THE STR. OVER THE
NEXT 12 TO 18 HOURS TD 30W WILL TRACK OVER THE PHILIPPINES. DESPITE
THE FAVORABLE ENVIRONMENTAL CONDITIONS, LAND INTERACTION WITH THE
ARCHIPELAGO WILL LIMIT THE POTENTIAL FOR INTENSIFICATION, AND TD 30W
IS FORECAST TO REMAIN A TROPICAL DEPRESSION DURING THIS TIME.
BETWEEN TAU 18 AND 24 THE SYSTEM WILL EMERGE OVER THE WARM WATERS OF
THE SOUTH CHINA SEA. UPPER-LEVEL CONDITIONS ARE FORECAST TO REMAIN
VERY FAVORABLE AND TD 30W WILL BEGIN A PERIOD OF RAPID
INTENSIFICATION, REACHING A PEAK INTENSITY OF 70 KNOTS AROUND TAU
48. THE SYSTEM IS ALSO EXPECTED TO REMAIN FAIRLY COMPACT WITH THE 34-
KNOT WIND RADII REMAINING CLOSE TO THE SYSTEM CENTER.
   C. IN THE EXTENDED PERIOD TD 30W WILL MOVE INTO AN AREA OF LOWER
SSTS, THIS COMBINED WITH DETERIORATING UPPER-LEVEL CONDITIONS WILL
RESULT IN A WEAKENING TREND BEGINNING JUST BEFORE TAU 72. AROUND TAU
96 THE STEERING RIDGE WILL HAVE WEAKENED SUFFICIENTLY TO CAUSE A
TRACK SHIFT TO THE NORTH-NORTHWEST STEERING TD 30W OVER HAINAN AND
CLOSER TO THE WESTERLY JET. LAND INTERACTION AND INCREASED WIND
SHEAR WILL FURTHER WEAKEN THE SYSTEM. DYNAMIC MODEL GUIDANCE SHOWS
VERY GOOD AGREEMENT IN THE MID-RANGE FORECAST DUE TO THE WELL-
ESTABLISHED DEEP-LAYERED STEERING RIDGE. HOWEVER THERE ARE SLIGHT
DIFFERENCES IN THE MODELS THAT ORIGINATE FROM THE INITIAL 12 HOURS
AND IN THE UNCERTAINTY OF THE TRACK WHILE OVER THE PHILIPPINES. BY
TAU 96 AND 120 MODELS ARE IN DISAGREEMENT WITH THE EXACT POSITION
AND TIMING OF THE TURN TO THE NORTH-NORTHWEST. DUE TO THESE
UNCERTAINTIES THERE IS OVERALL LOW CONFIDENCE IN THE FORECAST
TRACK.//
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