Tropical Storm KROVANH Advisory 12月20日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 26W (TWENTYSIX)
WARNING NR 001//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION 26W (TWENTYSIX), LOCATED APPROXIMATELY 433 NM
SOUTHWEST OF MANILA, PHILIPPINES, HAS TRACKED WESTWARD AT 15 KNOTS
OVER THE PAST SIX HOURS. TD 26W HAS CONSOLIDATED INTO A TROPICAL
CYCLONE AS THE LOW LEVEL CIRCULATION INTERACTS FAVORABLY WITH A
STRONG LOW-LEVEL NORTHEASTERLY SURGE TO THE WEST. THE CURRENT
POSITION IS SITUATED NEAR THE CENTER OF THE BROAD, LOW-LEVEL
CIRCULATION EVIDENT IN ANIMATED MULTI-SPECTRAL SATELLITE IMAGERY,
AND IS CONSISTENT WITH RECENT SUBJECTIVE POSITION FIXES FROM PGTW
AND KNES. THE INTENSITY IS SET SLIGHTLY ABOVE MULTI-AGENCY
SUBJECTIVE VORAK CURRENT INTENSITY ESTIMATES OF 25 KNOTS TO ACCOUNT
FOR STRONGER WINDS IN THE NORTHERN AND WESTERN PORTIONS OF THE
CIRCULATION, WHERE INTERACTION WITH THE NORTHEASTERLY SURGE FLOW IS
OCCURRING. DEEP CONVECTION IS CURRENTLY CONFINED PRIMARILY THE WEST
AND NORTHWEST OF THE CENTER, IN THE AREAS OF CONVERGENT STORM SURGE
FLOW. ENVIRONMENTAL CONDITIONS ARE MARGINALLY FAVORABLE FOR
DEVELOPMENT, WITH MODERATE VERTICAL WIND SHEAR (15-20 KTS), VERY
WARM SEA SURFACE TEMPERATURES (28-29C), AND PRONOUNCED POLEWARD
OUTFLOW ALOFT. THE SYSTEM IS TRACKING GENERALLY WESTWARD FOLLOWING
THE FLOW ASSOCIATED WITH A LOW TO MID-LAYER STEERING RIDGE TO THE
NORTH.
3. FORECAST REASONING.
   A. THIS IS THE FIRST PROGNOSTIC REASONING MESSAGE AND SETS THE
FORECAST PHILOSOPHY.
   B. TD 26W IS EXPECTED TO FOLLOW THE FLOW ASSOCIATED WITH
SUBTROPICAL RIDGING TO THE NORTH THROUGHOUT THE FORECAST PERIOD.
SLOW INTENSIFICATION IS EXPECTED IN THE NEAR-TERM AS INTENSIFYING
WINDS RESULTING FROM THE INTERACTION BETWEEN THE STORM AND
NORTHEASTERLY SURGE WRAP INTO THE STORM CIRCULATION, AND AS
MARGINALLY FAVORABLE ENVIRONMENTAL CONDITIONS SUPPORT CONVECTIVE
DEVELOPMENT. PERSISTENT VERTICAL WIND SHEAR, PASSAGE OVER SLIGHTLY
COOLER WATER AND SEPARATION OF THE STORM CIRCULATION FROM THE
SUPPORTING SURGE FLOW SHOULD LEAD TO A WEAKENING TREND BY TAU 36,
WHICH WILL CONTINUE THROUGH DISSIPATION. NUMERICAL MODEL GUIDANCE IS
IN GOOD AGREEMENT WITH THE OVERALL TRACK FORECAST SCENARIO, WITH
SMALL SPREAD THROUGH TAU 48. MODEL GUIDANCE DIVERGES AFTER THAT
POINT, WHEN STORM STRUCTURE AND INTERACTION WITH ENVIRONMENTAL FLOW
WILL LIKELY CHANGE RAPIDLY DUE TO WEAKENING. OVERALL, THERE IS HIGH
CONFIDENCE IN THE TRACK FORECAST THROUGH TAU 48 AND FAIR CONFIDENCE
BEYOND THAT POINT.
   C. TD 26W IS EXPECTED TO FULLY DISSIPATE BY TAU 96 AS IT
CONTINUES TRACKING WESTWARD TOWARD THE MALAY PENINSULA.//
NNNN
NNNN