Tropical Storm NANGKA Advisory 06 Ιουλ.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 11W (NANGKA) WARNING NR
10//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM 11W (NANGKA), LOCATED APPROXIMATELY 90 NM NORTH OF
UJELANG, HAS TRACKED WESTWARD AT 11 KNOTS OVER THE PAST SIX HOURS.
THE CURRENT POSITION IS BASED ON A 051732Z PGTW SATELLITE FIX AND A
051801Z SSMIS PASS. THE INTENSITY OF 55 KNOTS IS CONSISTENT
WITH A CONSENSUS OF DVORAK SATELLITE INTENSITY ESTIMATES FROM
MULTIPLE REPORTING AGENCIES. RECENT ANIMATED INFRARED SATELLITE
IMAGERY SHOWS DEEP CONVECTION PERSISTING NEAR THE CENTER OF A
TIGHTLY-WRAPPED LOW LEVEL CIRCULATION CENTER (LLCC) EVIDENT IN THE
1801Z SSMIS IMAGE. IMPROVING LOW LEVEL STRUCTURE HAS ACCOMPANIED A
STEADY INTENSIFICATION TREND OVER THE PAST SIX HOURS. THIS
INTENSIFICATION HAS BEEN SUPPORTED BY LOW VERTICAL WIND SHEAR AND
IMPROVING UPPER LEVEL OUTFLOW, INCLUDING A DEVELOPING POLEWARD
OUTFLOW CHANNEL ENHANCED BY A TROPICAL UPPER TROPOSPHERIC TROUGH
(TUTT) CELL TO THE NORTHEAST. TS 11W IS TRACKING ALONG THE PERIPHERY
OF A SUBTROPICAL STEERING RIDGE TO THE NORTH.
3. FORECAST REASONING.
   A. FORECAST INTENSITIES HAVE INCREASED SLIGHTLY, AND THE FORECAST
TRACK SPEED FOR THE TAU 96 TO TAU 120 PERIOD HAS DECREASED A BIT
FROM THE PREVIOUS WARNING. HOWEVER, THERE IS NO MAJOR CHANGE TO THE
FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TS 11W WILL CONTINUE TRACKING ALONG THE SUBTROPICAL STEERING
RIDGE PERIPHERY THROUGH THE NEXT 72 HOURS. WESTWARD MOTION WILL
GRADUALLY TRANSITION TO A MORE NORTHWESTWARD TRACK AS THE STEERING
RIDGE REORIENTS AHEAD OF A DEVELOPING MID-LATITUDE TROUGH. STEADY
INTENSIFICATION IS ANTICIPATED THROUGHOUT THE PERIOD AS VERTICAL
WIND SHEAR REMAINS GENERALLY FAVORABLE AND UPPER-LEVEL OUTFLOW IS
ENHANCED BY THE TUTT CELL TO THE NORTHEAST, AT LEAST IN THE NEAR-
TERM. DYNAMIC MODEL GUIDANCE IS IN GOOD AGREEMENT REGARDING THE
FORECAST TRACK THROUGH TAU 72. THE CURRENT TRACK FORECAST FOR THIS
PERIOD LIES CLOSE TO THE MULTI-MODEL CONSENSUS AND THE PREVIOUS JTWC
FORECAST.
   C. IN THE EXTENDED PERIOD, STORM MOTION IS EXPECTED TO SLOW AS A
DEVELOPING MID-LATITUDE TROUGH BEGINS WEAKENING THE STEERING RIDGE.
FUTHER INTENSIFICATION IS EXPECTED AS ENVIRONMENTAL CONDITIONS
REMAIN FAVORABLE, PARTICULARLY WITH POLEWARD OUTFLOW POTENTIAL
IMPROVING AHEAD OF THE DEVELOPING MID-LATITUDE TROUGH. DETERMINISTIC
AND ENSEMBLE MODEL GUIDANCE REMAIN IN GOOD AGREEMENT IN THE EXTENDED
RANGE, LENDING HIGH CONFIDENCE TO THE CURRENT TRACK FORECAST.//
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