Tropical Storm TAPAH Advisory dom, 27-04

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 06W (SIX) WARNING
NR 01//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION (TD) 06W (SIX), LOCATED APPROXIMATELY 144 NM
SOUTHEAST OF ANDERSEN AFB, HAS TRACKED AT 06 KNOTS OVER THE PAST SIX
HOURS. ANIMATED INFRARED (IR) SATELLITE IMAGERY DEPICTS A SLOWLY-
CONSOLIDATING LOW-LEVEL CIRCULATION CENTER (LLCC) WITH FORMATIVE
CONVECTIVE BANDING. A 270949Z SSMIS IMAGE DEPICTS A PARTIALLY-
EXPOSED LLCC WITH THE BULK OF THE DEEP CONVECTION CONFINED TO THE
EASTERN SEMI-CIRCLE. OVER THE PAST 12 HOURS, THE TOTAL PRECIPITABLE
WATER (TPW) PRODUCT INDICATES A STRONGER, MORE SYMMETRIC DEEP
MOISTURE ENVELOPE. THE INITIAL POSITION IS BASED ON A 271127Z METOP-
B IMAGE AS WELL AS THE RECENT PGTW POSITION FIX. A SHIP REPORT ABOUT
120 NM NORTH-NORTHWEST OF THE CURRENT CENTER INDICATED NORTH-
NORTHEASTERLY SUSTAINED WINDS AT 18 KNOTS WITH SLP NEAR 1006 MB.
BASED ON ALL AVAILABLE DATA, THE INITIAL INTENSITY IS ASSESSED AT 25
KNOTS, WHICH IS CONSISTENT WITH DVORAK INTENSITY ESTIMATES RANGING
FROM 25 TO 30 KNOTS. ANIMATED WATER VAPOR IMAGERY REVEALS A
DEVELOPING ANTICYCLONE OVER THE SYSTEM, WHICH IS PRODUCING A
FAVORABLE ENVIRONMENT CHARACTERIZED BY LOW VERTICAL WIND SHEAR AND
EXCELLENT POLEWARD OUTFLOW, ENHANCED BY A DEEP MIDLATITUDE TROUGH
EXTENDING SOUTHWESTWARD FROM A LOW POSITIONED NEAR 35N 155E. TD 06W
IS LOCATED ALONG THE WESTERN PERIPHERY OF A NORTH-SOUTH ORIENTED
SUBTROPICAL RIDGE (STR) AND IS TRACKING SLOWLY NORTHWARD TOWARD A
BREAK IN THE STR CREATED BY THE AFOREMENTIONED DEEP MIDLATITUDE
SHORTWAVE TROUGH.
3. FORECAST REASONING.
   A. THIS IS THE INITIAL PROGNOSTIC REASONING AND SETS THE FORECAST
PHILOSOPHY.
   B. TD 06W IS FORECAST TO CONTINUE TRACKING NORTHWARD ALONG THE
WESTERN PERIPHERY OF THE LOW-TO MID-LEVEL STR POSITIONED TO THE EAST
THROUGH TAU 36. AFTER TAU 36, THE SYSTEM SHOULD GRADUALLY TURN
NORTHWESTWARD AS THE STR BUILDS TO THE NORTH. AVAILABLE DYNAMIC
GUIDANCE IS LIMITED BUT IS IN GOOD AGREEMENT, HOWEVER, DUE TO
UNCERTAINTY IN POSITIONING AND IN THE TIMING OF THE NORTHWESTWARD
TURN, THERE IS OVERALL LOW CONFIDENCE IN THE JTWC FORECAST. TD 06W
ORIGINATED FROM A STRONG MID-LEVEL CIRCULATION AND IS FORECAST TO
CONTINUE INTENSIFYING SLOWLY AS THE LOW-LEVEL CIRCULATION CENTER
ORGANIZES. POLEWARD OUTFLOW IS EXPECTED TO REMAIN VIGOROUS THROUGH
TAU 48 AND SST WILL REMAIN MARGINALLY FAVORABLE AT ABOUT 28C. AFTER
TAU 48, INTERACTION WITH A WEAK BAROCLINIC ZONE IS EXPECTED TO
HINDER FURTHER DEVELOPMENT.
   C. IN THE EXTENDED TAUS, TD 06W IS FORECAST TO RE-CURVE AHEAD OF
AN APPROACHING SHORTWAVE TROUGH AND SHOULD ENCOUNTER INCREASING
VERTICAL WIND SHEAR AS WELL AS BEGIN INTERACTING WITH THE BAROCLINIC
ZONE AT WHICH POINT THE SYSTEM IS FORECAST TO WEAKEN. TD 06W IS
FORECAST TO DISSIPATE BY TAU 120.//
NNNN
NNNN