Tropical Storm LEKIMA Advisory pon., 21.10.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 28W (LEKIMA) WARNING NR
03//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM 28W (LEKIMA), LOCATED APPROXIMATELY 945 NM
EAST OF ANDERSEN AFB, HAS TRACKED NORTHWARD AT 08 KNOTS OVER
THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI)
DEPICTS A QUICKLY CONSOLIDATING SYSTEM WITH DEEPENING CENTRAL
CONVECTION AND FORMATIVE CURVED BANDING WRAPPING AROUND THE SYSTEM.
THIS RECENT IMPROVEMENT IN STRUCTURE IS EVIDENT IN A 202326Z AMSU-B
MICROWAVE IMAGE, WHICH REVEALS BANDING FEATURES SURROUNDING THE
SYSTEM WITH A STRONG BAND WRAPPING ACROSS THE EASTERN SEMI-CIRCLE.
THE INITIAL POSITION IS BASED ON THE MSI ANIMATION WITH FAIR
CONFIDENCE. THE INITIAL INTENSITY IS BASED ON AN AVERAGE OF DVORAK
ESTIMATES RANGING FROM 35-45 KNOTS. UPPER LEVEL ANALYSIS INDICATES
THE SYSTEM IS JUST TO THE EAST OF A WEAK TROUGH THAT IS CAUSING
SUBSIDENCE ALONG ITS NORTHWEST QUADRANT. HOWEVER, VIGOROUS EASTWARD
AND EQUATORWARD OUTFLOW ARE EVIDENT ON ANIMATED WATER VAPOR IMAGERY
AND HELPING SUSTAIN THE CONVECTION. THE CYCLONE IS CURRENTLY
TRACKING ALONG THE OUTERMOST PERIPHERY OF A LOW REFLECTION OF THE
SUBTROPICAL RIDGE (STR) WELL TO THE NORTH.
3. FORECAST REASONING.
   A. INTENSITY GUIDANCE HAS CHANGED TO REFLECT RAPID
INTENSIFICATION OVER THE NEXT 24 HOURS, THUS THE JTWC FORECAST
INTENSITIES HAVE BEEN ADJUSTED TO REFLECT THIS SCENARIO.
   B. THE STR WILL BE THE PRIMARY STEERING MECHANISM FOR TS 28W.
HENCE, THE SYSTEM IS EXPECTED TO TRACK GENERALLY NORTHWESTWARD OVER
THE NEXT 72 HOURS. RELATIVELY LOW VERTICAL WIND SHEAR (VWS) AND GOOD
EQUATORWARD OUTFLOW, IN ADDITION TO THE PERENNIALLY WARM SEA SURFACE
TEMPERATURES IN THE AREA, WILL ENSURE GRADUAL INTENSIFICATION.
LEKIMA WILL REACH TYPHOON INTENSITY BY TAU 36 AND 105 KNOTS BY TAU
72.
   C. AFTER TAU 72, TS 28W WILL BEGIN TO ROUND THE STR AXIS AND
TRACK ON A MORE POLEWARD DIRECTION. THE ADDITION OF A POLEWARD
OUTFLOW CHANNEL ASSOCIATED WITH THE MID-LATITUDE WESTERLIES WILL
ENHANCE FURTHER INTENSIFICATION, PEAKING AT 110 KNOTS BY TAU 96.
AFTER TAU 96, INCREASING VWS AND COOLING SEA SURFACE TEMPERATURES
WILL BEGIN TO ERODE THE SYSTEM. NUMERIC MODEL GUIDANCE ARE IN A
FAIRLY TIGHT AGREEMENT THROUGH 72, BUT INCREASINGLY DIVERGE AS THE
SYSTEM ROUNDS THE STR AFTERWARD. DUE TO THE UNCERTAINTY IN THE STORM
MOTION IN THE NEAR TERM AS THE SYSTEM CONTINUES TO CONSOLIDATE AS
WELL AS THE SPREAD IN THE GUIDANCE AFTER TAU 72, THE CONFIDENCE IN
THE JTWC TRACK FORECAST IS LOW.//
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