Tropical Storm HAGIBIS Advisory Sun Oct 06

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 20W (HAGIBIS)
WARNING NR 004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 20W (HAGIBIS), LOCATED APPROXIMATELY 638 NM
EAST OF ANDERSEN AFB, GUAM, HAS TRACKED WESTWARD AT 18 KNOTS OVER
THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY
DEPICTS A RAPIDLY CONSOLIDATING SYSTEM WITH TIGHTLY-CURVED DEEP
CONVECTIVE BANDING WRAPPING INTO A DEFINED LOW-LEVEL CIRCULATION
CENTER (LLCC). A 052242Z MHS 89GHZ COLOR COMPOSITE IMAGE SHOWS A
PARTIALLY-EXPOSED LLCC WITH CONVECTIVE BANDING WRAPPING INTO THE
SOUTHEAST QUADRANT. OVERALL, THERE IS FAIR CONFIDENCE IN THE CURRENT
POSITION. UPPER-LEVEL ANALYSIS INDICATES NEAR-RADIAL OUTFLOW WITH
LOW VERTICAL WIND SHEAR. SST VALUES OF 30-31C AND HIGH OCEAN HEAT
CONTENT VALUES ALSO SUPPORT SIGNIFICANT INTENSIFICATION. THE CURRENT
INTENSITY IS ASSESSED AT 45 KNOTS, HEDGED ABOVE DVORAK INTENSITY
ESTIMATES OF T2.5 (35 KNOTS), BASED ON A 05/2340Z ADT ESTIMATE OF
T2.9 (APPROXIMATELY 45 KNOTS). THE SYSTEM IS TRACKING ALONG THE
SOUTHERN PERIPHERY OF A DEEP-LAYERED SUBTROPICAL RIDGE (STR)
ENTRENCHED TO THE NORTH.
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM
THE PREVIOUS PROGNOSTIC REASONING MESSAGE. ADDITIONALLY, THIS
FORECAST REMAINS HIGHLY CONSISTENT WITH THE PREVIOUS JTWC FORECAST.
   B. TS 20W IS FORECAST TO TRACK WESTWARD TO WEST-NORTHWESTWARD
THROUGH TAU 72 UNDER THE STEERING INFLUENCE OF THE STR.
ENVIRONMENTAL CONDITIONS ARE EXPECTED TO REMAIN VERY FAVORABLE
THROUGH THE FORECAST PERIOD WITH ROBUST OUTFLOW, WARM SST AND HIGH
OCEAN HEAT CONTENT VALUES SUPPORTING PERIODS OF RAPID
INTENSIFICATION (RI). JTWC INTENSITY GUIDANCE CONTINUES TO INDICATE
SOME POTENTIAL FOR RI WITHIN THE NEXT 36 HOURS, BEFORE THE SYSTEM
HITS THE NORTHERN MARIANAS. THIS FORECAST INDICATES A TYPHOON-
STRENGTH SYSTEM (75-80 KNOTS) IMPACTING THE NORTHERN MARIANAS,
HOWEVER, THERE IS UNCERTAINTY IN THE EXACT INTENSITY WITH POTENTIAL
FOR A STRONGER SYSTEM. OVERALL, THERE IS HIGH CONFIDENCE IN THE JTWC
TRACK FORECAST THROUGH TAU 36 WITH A 32 NM SPREAD IN SOLUTIONS AT
TAU 36. AFTER TAU 36, TS 20W WILL CONTINUE TO INTENSIFY UNDER
FAVORABLE CONDITIONS.
   C. IN THE EXTENDED PERIOD, TS 20W WILL GENERALLY TRACK
NORTHWESTWARD TOWARD A BREAK IN THE STR ASSOCIATED WITH A DEEP,
DYNAMIC SHORTWAVE TROUGH FORECAST TO DEEPEN OVER WESTERN JAPAN.
IMPROVED POLEWARD OUTFLOW ASSOCIATED WITH THIS SHORTWAVE TROUGH WILL
AID IN BOOSTING THE INTENSITY TO SUPER TYPHOON STRENGTH. THERE IS
INCREASING UNCERTAINTY AFTER TAU 96 AS THE NUMERICAL MODEL GUIDANCE
DIVERGES WITH A 200 NM SPREAD IN SOLUTIONS AT TAU 120, THEREFORE,
THERE IS NOW MODERATE CONFIDENCE IN THE JTWC TRACK FORECAST.//
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