Tropical Storm DUJUAN Advisory di, 22-09

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 21W (TWENTYONE)
WARNING NR 02//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION (TD) 21W (TWENTYONE) LOCATED APPROXIMATELY
297 NM NORTHWEST OF NAVSTA GUAM, HAS TRACKED WEST-NORTHWESTWARD AT 12
KNOTS OVER THE PAST SIX HOURS. ANIMATED MSI SHOWS PERSISTENT
SYMMETRICAL DEEP CONVECTION AND A LOW LEVER SPINNER TO THE EAST. A
212141Z SSMIS 37 GHZ IMAGE SHOWS SOME CURVATURE IN THE LOW LEVELS
NEAR THE BEST TRACK, GIVING SOME, ALBEIT VERY SLIGHT, CONFIDENCE IN
THE OVERALL POSITION OF THE SYSTEM DUE TO THE MULTIPLE VORTICES
PRESENT. THE INITIAL INTENSITY IS HELD AT 25 KNOTS AS DT ESTIMATES
RANGE FROM 1.0 TO 1.5. UPPER LEVEL ANALYSIS INDICATES 15 TO 25 KNOTS
OF EASTERLY VWS  OFFSET BY GOOD DIVERGENCE ALOFT. THE SYSTEM IS
CURRENTLY TRACKING ON THE SOUTHERN SIDE OF A STR TO THE NORTH.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TD 21W WILL TRACK TO THE WEST-NORTHWEST UNDER THE INFLUENCE OF
THE STR THROUGH TAU 36 WITH MARGINAL INTENSIFICATION. EXPECT A MORE
POLEWARD TREND IN THE TRACK AS A MID-LATITUDE SHORTWAVE TROUGH WILL
CREATE A SMALL BREAK IN THE STR. EXPECT CONTINUED INTENSIFICATION OF
THE SYSTEM AS OUTFLOW IMPROVES BY TAU 48 THROUGH THE END OF THE
FORECAST PERIOD, EXCEEDING TYPHOON STRENGTH BY TAU 72.
   C. IN THE EXTENDED FORECAST, TD 21W WILL CONTINUE TO INTENSIFY AS
POLEWARD OUTFLOW IMPROVES AND OHC REMAINS CONDUCIVE. THE SYSTEM WILL
CONTINUE TO TRACK POLEWARD THROUGH THE BREAK IN THE RIDGE. DYNAMIC
MODEL GUIDANCE REMAINS FAIRLY SPREAD DUE TO THE SIGNIFICANCE AND
TIMING OF THE BREAK IN THE RIDGE. THERE REMAINS LOW CONFIDENCE IN
THE JTWC FORECAST TRACK.//
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