Tropical Storm HAIMA Advisory ma, 17-10

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 25W (HAIMA) WARNING NR 10//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON 25W (HAIMA), LOCATED APPROXIMATELY 225 NM NORTH-NORTHWEST
OF YAP, HAS TRACKED WEST-NORTHWESTWARD AT 14 KNOTS OVER THE PAST
SIX HOURS. ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY
DEPICTS DEEP CONVECTION WRAPPING INTO AN INTERMITTENT EYE FEATURE.
THE INITIAL POSITION IS PLACED WITH GOOD CONFIDENCE BASED ON EIR AND
MULTISPECTRAL SATELLITE IMAGERY. CONVECTIVE BANDING CONTINUES TO
GRADUALLY IMPROVE. HOWEVER, AFTER A STEEPER INTENSIFICATION RATE
EARLIER TODAY, THE IMPROVEMENT IN CONVECTIVE ORGANIZATION HAS SLOWED
SOMEWHAT IN THE LAST 6 HOURS. THE INITIAL INTENSITY IS
CONSERVATIVELY
INCREASED SLIGHTLY TO 100 KNOTS BASED ON A DVORAK CI OF T5.5 FROM
PGTW.
TY 25W CONTINUES TO BE IN A FAVORABLE ENVIRONMENT WITH WARM SSTS,
EXCELLENT RADIAL OUTFLOW, AND LOW VERTICAL WIND SHEAR. IT IS
TRACKING
UNDER THE STEERING INFLUENCE OF A SUBTROPICAL RIDGE (STR) TO THE
NORTH.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING BULLETIN.
   B. TY 25W IS EXPECTED TO CONTINUE TRACKING WEST-NORTHWESTWARD TO
NORTHWESTWARD UNDER THE STEERING INFLUENCE OF THE CURRENT STR TO THE
NORTH. ENVIRONMENTAL CONDITIONS WILL FAVOR CONTINUED DEEPENING. ONCE
THE DEEP CONVECTION WRAPS AROUND THE LLCC MORE SYMMETRICALLY, A
PHASE OF RAPID INTENSIFICATION IS LIKELY. TY 25W IS EXPECTED TO
REACH A PEAK OF SUPER TYPHOON INTENSITY IN THE NEXT 1 TO
2 DAYS. THEREAFTER, THE STEERING INFLUENCE WILL TRANSITION TO
ANOTHER STR CENTERED NEAR TAIWAN. DURING THIS TRANSITION, THE
POLEWARD OUTFLOW MAY BECOME RESTRICTED STARTING AROUND TAU 48,
LEADING TO SOME SLIGHT WEAKENING AS THE SYSTEM APPROACHES LUZON.
   C. BEYOND TAU 72, TY 25W WILL TURN POLEWARD INTO A BREAK IN THE
STR. THE INTENSITY FORECAST FOR THIS PERIOD WILL DEPEND ON HOW CLOSE
THE SYSTEM GETS TO LUZON. AT THIS TIME, THE INTENSITY FORECAST
CONSIDERS THE SCENARIO OF A CLOSE APPROACH BUT NO LANDFALL. AFTER
TAU 72, GLOBAL MODEL GUIDANCE DIVERGES, BUT THE SYSTEM WILL LIKELY
TURN TOWARD MAINLAND CHINA. DYNAMIC MODEL GUIDANCE REMAINS IN GOOD
AGREEMENT ONLY UP THROUGH TAU 72, SO THERE IS HIGH CONFIDENCE IN THE
JTWC FORECAST TRACK UP TO TAU 72 AND LOW CONFIDENCE THEREAFTER.//
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