Tropical Storm TWENTYSEVEN Advisory dom, 20.10.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 27W (TWENTYSEVEN)
WARNING NR 04//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION 27W (TWENTYSEVEN), LOCATED APPROXIMATELY 370
NM EAST-SOUTHEAST OF IWO TO, HAS TRACKED WEST-NORTHWESTWARD
AT 17 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL
SATELLITE IMAGERY DEPICTS A CONSOLIDATED LOW-LEVEL CIRCULATION
CENTER (LLCC) WITH DEEPENING CENTRAL CONVECTION AS WELL AS AN AREA
OF SHALLOWER CONVECTION SHEARED TO THE SOUTH. A 192224Z SSMIS
MICROWAVE IMAGE REVEALS THE LLCC POSITION WITH IMPROVING CENTRAL
CONVECTION OVERHEAD. THE INITIAL POSITION IS BASED ON THE ABOVE
ANIMATION AND AFOREMENTIONED MICROWAVE IMAGERY WITH HIGH CONFIDENCE.
THE INITIAL INTENSITY OF 25 KNOTS IS SUPPORTED BY DVORAK ESTIMATES
FROM PGTW AND KNES. UPPER LEVEL ANALYSIS INDICATES THE SYSTEM IS
SOUTH OF THE SUBTROPICAL RIDGE (STR) AXIS IN AN AREA OF STRONG (30-
40 KNOT) VERTICAL WIND SHEAR (VWS). HOWEVER, ANIMATED WATER VAPOR
IMAGERY CONTINUES TO SHOW AN EQUATORWARD OUTFLOW CHANNEL THAT IS
SUSTAINING THE ASSOCIATED CONVECTION. THE CYCLONE IS TRACKING ALONG
THE SOUTHWESTERN PERIPHERY OF A LOW-LEVEL REFLECTION OF THE STR TO
THE NORTHEAST.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE PREVIOUS FORECAST PHILOSOPHY FROM
THE PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TD 27W IS EXPECTED TO CONTINUE ALONG ITS CURRENT TRACK AROUND
THE WESTERN PERIPHERY OF A LOW-LEVEL REFLECTION OF THE STR
THROUGHOUT ITS SHORT LIFESPAN. IMPROVING CENTRAL CONVECTION WILL
ALLOW FOR A SLIGHT INTENSIFICATION TO 30 KNOTS BY TAU 12. AFTER THAT
THE STRONG VWS, WHICH WILL INCREASE TO 45 KNOTS AS THE CYCLONE MOVES
FURTHER POLEWARD AND BEGINS TO CREST THE STR AXIS, WILL CONTINUE TO
ERODE THE SYSTEM. ADDITIONALLY, SSTS COOLING TO BELOW 26 DEGREES
CELSIUS WILL DISRUPT THE LOW LEVEL INFLOW AND DISSIPATE THE SYSTEM
BELOW THE 25-KNOT WARNING THRESHOLD BY TAU 36. THE LIMITED DYNAMICAL
MODEL GUIDANCE IS IN FAIRLY TIGHT AGREEMENT. HOWEVER, GIVEN THE
FRAGILE STRUCTURE OF THE SYSTEM, CONFIDENCE IN THE JTWC FORECAST
TRACK REMAINS LOW.//
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