Tropical Storm DANAS Advisory ср, 17.07.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 06W (DANAS)
WARNING NR 03//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL STORM 06W (DANAS), LOCATED APPROXIMATELY 209 NM NORTHEAST OF
MANILA, PHILIPPINES, HAS TRACKED WESTWARD AT 03 KNOTS OVER THE PAST
SIX HOURS. THE CURRENT POSITION IS BASED ON A RECENT SATELLITE FIX
FROM PGTW AND 161741Z AMSR2 IMAGERY SHOWING A WELL-DEFINED LOW-LEVEL
CIRCULATION CENTER (LLCC). THE INTENSITY OF 35 KNOTS IS BASED ON
ASCAT PASSES FROM 161244Z AND 161311Z INDICATING EXTENSIVE COVERAGE
OF 30 TO 35 KNOT WINDS. FORWARD MOTION OF THE SYSTEM HAS SLOWED
SIGNIFICANTLY OVER THE PAST SIX HOURS UNDER THE COMPETING STEERING
INFLUENCES OF SUBTROPICAL RIDGING POSITIONED TO THE NORTHWEST AND
NEAR-EQUATORIAL RIDGING TO THE SOUTHEAST. THE MAJORITY OF DEEP
CONVECTION ASSOCIATED WITH THE SYSTEM HAS BEEN DISPLACED WELL TO THE
WEST OF THE CIRCULATION CENTER DUE TO MODERATE TO HIGH EASTERLY
VERTICAL WIND SHEAR (20-25 KNOTS), LEAVING THE LOW-LEVEL CIRCULATION
PARTIALLY EXPOSED. WARM SEA SURFACE TEMPERATURES (30-31 CELSIUS) AND
STRONG WESTWARD AND EQUATORWARD OUTFLOW ALOFT ARE ALSO OBSERVED.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. RECENT SLOW MOTION SUGGESTS THAT TS 06W IS UNDERGOING A
STEERING CHANGE, WHICH WILL MOST LIKELY RESULT IN A
PREVIOUSLY-ANTICIPATED POLEWARD TURN. A REORIENTING SUBTROPICAL RIDGE
TO THE EAST IS EXPECTED TO BECOME THE PRIMARY STEERING INFLUENCE,
TAKING THE SYSTEM CENTER TOWARD TAIWAN BY TAU 36 AND THE EASTERN
COAST OF MAINLAND CHINA BY TAU 72. THE WIND FIELD IS EXPECTED TO
REMAIN EXTENSIVE. SLOW INTENSIFICATION IS EXPECTED IN THE NEAR-TERM
AS VERTICAL WIND SHEAR AND LAND INTERACTION COUNTERACT THE FAVORABLE
INFLUENCES OF PASSAGE OVER WARM WATER AND STRONG OUTFLOW ALOFT.
FORECAST MODELS GENERALLY AGREE WITH THE OVERALL TRACK FORECAST
SCENARIO, BUT THERE IS SIGNIFICANT SPREAD BETWEEN THE WESTERN
OUTLIER, ECMWF, AND A GROUPING OF MODELS PREDICTING A TRACK FARTHER
TO THE EAST, INCLUDING THE UKMET MODEL. THE LOW-LEVEL CIRCULATION
PATTERN NEAR TS 06W REMAINS COMPLEX, WHICH IS INFLUENCING THE OUTCOME
OF THE MODEL FORECASTS. THE CURRENT FORECAST FOLLOWS THE MOST
PROBABLE ORIENTATION OF THE LARGE-SCALE FLOW PATTERN, IS CONSISTENT
WITH THE PREVIOUS JTWC FORECAST AND LIES SLIGHTLY TO THE WEST OF THE
MULTI-MODEL CONSENSUS. GIVEN NOTED SPREAD IN THE GUIDANCE, CONFIDENCE
IN THE JTWC TRACK FORECAST IS LOW.
   C. IN THE EXTENDED RANGE, TS 06W IS EXPECTED TO CONTINUE POLEWARD
AND EASTWARD AND BEGIN EXTRATROPICAL TRANSITION AS IT ENCOUNTERS A
DEVELOPING MID-LATITUDE TROUGH. SOME WEAKENING IS ANTICIPATED,
ALTHOUGH FAVORABLE BAROCLINIC INTERACTION WITH THE DEVELOPING TROUGH
SHOULD ALLOW THE SYSTEM TO MAINTAIN GALE FORCE OR STRONGER WINDS
DURING THE TRANSITION. THE STORM TRACK DURING THE EXTENDED PERIOD IS
HIGHLY DEPENDENT ON THE SOMEWHAT UNCERTAIN NEAR TO MEDIUM-TERM TRACK,
SO CONFIDENCE IN THE EXTENDED FORECAST TRACK IS ALSO LOW.//
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