Tropical Storm ONE Advisory Dom, 06-01

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 01W (ONE) WARNING
NR 007//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION (TD) 01W (ONE), LOCATED APPROXIMATELY 182 NM
EAST-SOUTHEAST OF MAJURO, HAS TRACKED NORTHWESTWARD AT 08 KNOTS
(KTS) OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY (MSI) SHOWS FLARING CONVECTION OVER A BROAD LOW LEVEL
CIRCULATION (LLC). THERE IS LOW CONFIDENCE IN THE INITIAL POSITION
WHICH WAS DETERMINED USING A COMBINATION OF THE MSI IMAGERY, AN
060424Z AMSU 89 GHZ MICROWAVE IMAGE, AND AN 060344Z SSMIS 37 GHZ
MICROWAVE IMAGE WHICH ALL SHOW WEAK BANDING FEATURES WRAPPING AROUND
THE BROAD CIRCULATION. THE ENVIRONMENT IS SOMEWHAT FAVORABLE WITH
LIGHT TO MODERATE (10-20 KT) VERTICAL WIND SHEAR (VWS), WEAK RADIAL
OUTFLOW, AND WARM (29-30 CELSIUS) SEA SURFACE TEMPERATURE. THE
CYCLONE IS TRACKING SLOWLY TOWARD A BREAK IN A SUBTROPICAL RIDGE
(STR) TO THE NORTH.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TD 01W WILL SLOWLY TURN WEST-NORTHWESTWARD AND ACCELERATE AS
THE STR TO THE NORTH BUILDS. MARGINAL ENVIRONMENTAL CONDITIONS ARE
EXPECTED TO PERSIST AND SHOULD ALLOW FOR LIMITED INTENSIFICATION
THROUGH TAU 72. THE ECMWF MODEL IS A SOUTHERN OUTLIER, SHOWING A
WESTWARD TRACK THROUGH TAU 72. NAVGEM BEGINS TO DEVIATE FROM THE
OTHER MODELS BY TAU 24, AS IT MAINTAINS A MORE NORTHWESTWARD TRACK.
FOR THIS PORTION OF THE FORECAST, THE JTWC TRACK FORECAST CLOSELY
FOLLOWS THE OTHER MEMBERS.
   C. BEYOND TAU 72, TD 01W WILL CONTINUE ON A WEST-NORTHWESTWARD
TRACK AND INTENSIFY SLIGHTLY UNDER CONTINUED MARGINALLY FAVORABLE
ENVIRONMENTAL CONDITIONS. SPREAD OF 670 NM AT TAU 120 IN THE MODEL
GUIDANCE IS LARGELY DUE TO THE SOUTHERN (ECMWF) AND NORTHERN
(NAVGEM) OUTLIERS. DISCOUNTING THOSE MODELS, THE SPREAD IS REDUCED
TO ABOUT 215 NM AT TAU 120. THE JTWC FORECAST TRACK IS PLACED NEAR
THE BULK OF THE GUIDANCE WITH LOW CONFIDENCE DUE PRIMARILY TO HIGH
UNCERTAINTY IN THE INITIAL POSITION.//
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