Tropical Storm NANGKA Advisory sáb, 04-07

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 11W (NANGKA) WARNING NR
03//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM 11W (NANGKA), LOCATED APPROXIMATELY 130 NM EAST-
NORTHEAST OF KWAJALEIN, HAS TRACKED WEST-NORTHWESTWARD AT 08
KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY DEPICTS A TIGHTLY WRAPPED SYSTEM WITH SEVERAL CONVECTIVE
BANDS WRAPPING INTO THE SYSTEM CENTER. A SLOT OF DRY AIR IS ALSO
EVIDENT TO THE WEST OF TS NANGKA WHICH APPEARS TO BE LIMITING
CONVECTIVE GROWTH ACROSS THE CORRESPONDING QUADRANT OF THE SYSTEM. A
032238Z METOP-A MICROWAVE IMAGE REVEALS THE LLCC WHICH IS OBSCURED
BY CONVECTION IN THE MSI AS WELL AS VERIFIES THE DRY AIR SLOT TO THE
WEST OF THE SYSTEM. THE INITIAL POSITION IS BASED ON THE
AFOREMENTIONED MICROWAVE IMAGE AND IN GOOD AGREEMENT WITH THE 00Z
PGTW FIX POSITION. THE INITIAL INTENSITY IS ASSESSED AT 40 KTS BASED
ON THE 032151Z ASCAT IMAGE WHICH SHOWS 40 KNOT WIND BARBS ACROSS THE
NORTHERN SEMI-CIRCLE OF TS 11W. UPPER LEVEL ANALYSIS INDICATES A
FAVORABLE ENVIRONMENT WITH 5-15 KTS VERTICAL WIND SHEAR AND GOOD
POLEWARD OUTFLOW. TS 11W IS CURRENTLY TRACKING WEST-NORTHWEST ALONG
THE SOUTHERN PERIPHERY OF THE SUBTROPICAL RIDGE TO THE NORTH.
3. FORECAST REASONING.
   A. NO CHANGE TO FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC
REASONING MESSAGE.
   B. TS 11W IS EXPECTED TO CONTINUE TRACKING WEST-NORTHWEST ALONG
THE SOUTHERN PERIPHERY OF THE STR THROUGH TAU 48. TRACK SPEEDS HAVE
SLIGHTLY SLOWED FROM THE PREVIOUS WARNING, BUT ARE EXPECTED TO
REMAIN STEADY THROUGH TAU 48. INTENSIFICATION MAY BE LIMITED OVER
THE NEXT 12-24 HOURS AS A SLOT OF DRY AIR TO THE WEST OF THE SYSTEM
IS ENTRAINED, HOWEVER, DUE TO THE STRONG MOISTURE TAP TO THE SOUTH
AND EAST OF THE SYSTEM TS 11W IS EXPECTED TO OVERCOME THIS
UNFAVORABLE POCKET OF AIR. STEADY INTENSIFICATION IS EXPECTED
THEREAFTER DUE TO FAVORABLE UPPER LEVEL CONDITIONS AS WELL AS WARM
SSTS AND POSITIVE OHC VALUES. AFTER TAU 48 NANGKA IS EXPECTED TO
TURN SLIGHTLY MORE POLEWARD AND BEGIN TRACKING TO THE NORTHWEST.
   C. TS 11W IS EXPECTED TO CONTINUE ON THE NORTHWEST TRAJECTORY
THROUGH TAU 120. STEADY INTENSIFICATION IS EXPECTED TO REACH A PEAK
INTENSITY OF 90 KTS BY THE END OF THE FORECAST PERIOD. DYNAMIC MODEL
GUIDANCE IS IN TIGHT AGREEMENT, LENDING HIGH CONFIDENCE TO THE JTWC
FORECAST TRACK. HOWEVER, DUE TO THE DYNAMIC PATTERN CURRENTLY
OBSERVED IN THE WESTERN PACIFIC, CLOSE ATTENTION SHOULD ALSO BE PAID
TO THE EVOLUTION OF TS 09W AND THE TROUGH NORTH OF THE SYSTEM WHICH
IS SLOWLY RETREATING POLEWARD.//
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