Tropical Storm KROSA Advisory 07.08.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 11W (KROSA) WARNING
NR 006//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 11W (KROSA), LOCATED APPROXIMATELY 253 NM
SOUTH OF IWO TO, HAS TRACKED NORTH-NORTHWESTWARD AT 11 KNOTS OVER
THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY SHOWS
DEEP CONVECTIVE BANDING WRAPPING TIGHTLY AROUND THE LOW LEVEL
CIRCULATION CENTER (LLCC). THE CONVECTIVE BANDING EXTENDS TO THE
SOUTH AND WEST. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE
AND IS BASED ON A 070039Z METOP-B ASCAT IMAGE WHICH CLEARLY SHOWS
THE LLCC. THE INITIAL INTENSITY OF 55 KNOTS IS HEDGED SLIGHTLY ABOVE
THE ASCAT PASS WHICH SHOWS 50 KNOTS AND BASED ON A DVORAK CURRENT
INTENSITY (CI) ESTIMATE OF T3.5 (55 KNOTS) FROM PGTW. ENVIRONMENTAL
ANALYSIS SHOW THAT TS 11W IS EXPERIENCING FAVORABLE VERTICAL WIND
SHEAR (15 KNOTS). THE EQUATORWARD OUTFLOW CHANNEL REMAINS STRONG AND
THE POLEWARD OUTFLOW CHANNEL REMAINS WEAK WHICH HAS INHIBITED
FURTHER INTENSIFICATION. SEA SURFACE TEMPERATURES REMAIN FAVORABLE,
GREATER THAN 31 DEGREES CELSIUS. TS 11W IS TRACKING NORTH-
NORTHWESTWARD ALONG THE SOUTHWESTERN PERIPHERY OF A SUBTROPICAL
RIDGE (STR) LOCATED TO THE NORTHEAST.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE OVERALL FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TS 11W WILL TRACK NORTH-NORTHWESTWARD WHILE UNDER THE
INFLUENCE OF THE AFOREMENTIONED STR THROUGH TAU 24. FAVORABLE SEA
SURFACE TEMPERATURES AND FAVORABLE VERTICAL WIND SHEAR WILL ALLOW
FOR A STEADY INCREASE IN INTENSITY, REACHING 80 KNOTS BY TAU 72. A
LIMITED POLEWARD OUTFLOW CHANNEL WILL PREVENT FURTHER
INTENSIFICATION IN THE SHORT TERM. BY TAU 24, AN APPROACHING WEST TO
EAST MOVING SHORTWAVE TROUGH WILL CAUSE A TEMPORARY BREAK IN THE STR
AND ALLOW TS 11W TO TRACK NORTHEASTWARD THROUGH TAU 72. THERE IS A
WIDE SPREAD IN NUMERICAL MODEL GUIDANCE. HOWEVER, MODELS DO AGREE IN
AN INITIAL NORTH-NORTHWESTWARD TRACK FOLLOWED BY A NORTHEASTWARD
TURN. HOWEVER, MODELS DISAGREE ON THE TIMING AND SHARPNESS OF THE
TURN. THEREFORE, THERE IS LOW CONFIDENCE IN THIS PORTION OF THE JTWC
FORECAST TRACK.
   C. IN THE EXTENDED FORECAST PERIOD, THE MAJORITY OF THE MODELS
INDICATE THAT THE STR WILL BUILD WESTWARD AFTER THE PASSAGE OF THE
SHORTWAVE TROUGH AND ALLOW TS 11W TO TRACK BACK TOWARD THE
NORTHWEST. THE NOTABLE EXCEPTION IS THE NAVGEM SOLUTION WHICH SHOWS
A WEAKER STR AND DOES NOT TURN TS 11W BACK TO THE NORTHWEST.
INSTEAD, NAVGEM INDICATES A NORTHEASTWARD TRACK BEYOND TAU 72. THE
GFS ENSEMBLE ALSO INDICATES A MORE NORTHWARD TRACK BEYOND TAU 72.
THE JTWC FORECAST TRACK IS PLACED NEAR THE MULTI-MODEL CONSENSUS AND
FAVORS THE ECMWF AND UKMET SOLUTIONS WHICH INDICATE A NORTHWESTWARD
TRACK IN THE EXTENDED FORECAST. THERE IS A MODEL SPREAD OF 350 NM BY
TAU 120 WITH THE UKMET SOLUTION ON THE WESTERN EDGE OF THE CONSENSUS
AND NAVGEM ON THE EASTERN EDGE OF THE CONSENSUS. DUE TO THE WIDE
RANGE OF MODEL SOLUTIONS THERE IS LOW CONFIDENCE IN THIS PORTION OF
THE JTWC FORECAST TRACK.//
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