Tropical Storm ONE Advisory Sa, 21.07.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 01C (HALOLA)
WARNING NR 43//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
  TROPICAL STORM 01C (HALOLA), LOCATED APPROXIMATELY 289 NM
SOUTHEAST OF IWO TO, HAS TRACKED WESTWARD AT 08 KNOTS OVER THE
PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE
IMAGERY DEPICTS TIGHTLY CURVED BANDING WRAPPING AROUND THE NORTHERN
CORE OF THE CYCLONE INTO A WELL-CONSOLIDATED LOW LEVEL CIRCULATION
CENTER (LLCC). THE CIMSS TOTAL PRECIPITABLE WATER ANIMATION SHOWS A
RADIALLY EXPANDING MOISTURE FIELD WITH AN ENHANCED EQUATORWARD
OUTFLOW. A 201710Z AMSU-B MICROWAVE IMAGE DEPICTS A DEVELOPING
MICROWAVE EYE FEATURE SURROUNDED BY TIGHTLY CURVED BANDING. THE
INITIAL POSITION IS BASED ON THE AFOREMENTIONED IMAGERY WITH HIGH
CONFIDENCE. THE CURRENT INTENSITY HAS BEEN INCREASED TO 55
KNOTS BASED ON CONGRUENT DVORAK CURRENT INTENSITY ESTIMATES FROM
PGTW AND RJTD. THE RECENT INTENSIFICATION HAS BEEN ACCELERATED BY
LOW VERTICAL WIND SHEAR (VWS), EXCELLENT DIFFLUENCE ALOFT, AND WARM
SEA SURFACE TEMPERATURES (SSTS). TS 01C IS TRACKING ALONG THE
SOUTHERN PERIPHERY OF THE DEEP-LAYERED STR.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TS HALOLA WILL CONTINUE TRACKING ON A WEST-NORTHWESTWARD
TRAJECTORY UNDER THE STEERING INFLUENCE OF THE DOMINANT STR THROUGH
TAU 72. THE SYSTEM IS FORECAST TO INTENSIFY OVER THE NEXT 36 HOURS
DUE TO FAVORABLE ENVIRONMENTAL CONDITIONS WITH GOOD OUTFLOW, LOW
VWS, AND SSTS ABOVE 28 CELSIUS. BEYOND TAU 36, VWS WILL REACH 20 TO
25 KNOTS WHICH WILL CAUSE THE RATE OF INTENSIFICATION TO DECREASE.
DYNAMIC MODEL GUIDANCE IS IN TIGHT AGREEMENT THROUGH TAU 72, LENDING
TO HIGH CONFIDENCE IN THIS PORTION OF THE FORECAST.
   C. IN THE EXTENDED TAUS, THE SYSTEM WILL BEGIN TO TURN POLEWARD
AS IT ROUNDS THE SOUTHWESTERN PERIPHERY OF THE STEERING STR. TS
HALOLA SHOULD BEGIN TO WEAKEN DUE TO VWS ABOVE 30 KNOTS,
DUE TO STRONG NORTHERLY FLOW FROM A BUILDING MID-LATITUDE RIDGE TO
THE NORTHWEST, AND SSTS DROPPING BELOW 26 CELSIUS. DYNAMIC MODEL
GUIDANCE SPREADS OUT AFTER TAU 72 DUE TO VARYING DEGREES IN THE
TIMING OF THE RE-CURVE. THIS FORECAST AGAIN SHIFTED SLIGHTLY FURTHER
WESTWARD FROM THE PREVIOUS FORECAST DUE TO VARYING MODEL SOLUTIONS
TO THE EXTENT OF THE STR TO THE NORTH. THIS UNCERTAINTY LEADS TO AN
OVERALL LOW CONFIDENCE IN THE JTWC FORECAST. AT THIS TIME, TS HALOLA
IS NOT EXPECTED TO UNDERGO EXTRA-TROPICAL TRANSITION SOUTH OF JAPAN
DUE TO THE POSITIONING OF THE BAROCLINIC ZONE NEAR 40 DEGREES
LATITUDE.//
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