Tropical Storm NURI Advisory Fri Oct 31

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 20W (TWENTY)
WARNING NR 01//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION (TD) 20W (TWENTY), LOCATED APPROXIMATELY 199 NM
NORTH-NORTHWEST OF YAP, HAS TRACKED WESTWARD AT 07 KNOTS OVER THE PAST
SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY SHOWS THE SYSTEM
HAS BEGUN TO CONSOLIDATE AS FORMATIVE BANDS FEEDING IN FROM THE
EASTERN AND SOUTHERN FLANKS WRAPPED TIGHTER INTO THE LOW LEVEL
CIRCULATION CENTER THAT IS CURRENTLY OBSCURED BY A CENTRAL DENSE
OVERCAST CLOUD FEATURE. THE INITIAL POSITION IS BASED ON THE ABOVE
ANIMATION AND EXTRAPOLATED FROM A 302308Z 37V SSMIS MICROWAVE PASS.
THE INITIAL INTENSITY IS BASED ON THE DVORAK ESTIMATES FROM PGTW AND
RJTD. UPPER LEVEL ANALYSIS INDICATES THE SYSTEM IS APPROXIMATELY 04
DEGREES SOUTH OF THE RIDGE AXIS IN AN AREA WITH LOW (05-10 KNOT)
VERTICAL WIND SHEAR. ADDITIONALLY, ANIMATED WATER VAPOR IMAGERY SHOWS
A ROBUST POLEWARD OUTFLOW INTO A TROUGH TO THE NORTHEAST THAT IS
PROVIDING VENTILATION TO THE ASSOCIATED CONVECTION. THE CYCLONE IS
TRACKING ALONG THE SOUTHERN PERIPHERY OF AN EXTENSION OF THE LOW- TO
MID-LAYERED SUBTROPICAL RIDGE (STR) TO THE NORTHEAST.
3. FORECAST REASONING.
   A. THIS IS THE FIRST PROGNOSTIC REASONING BULLETIN ON THIS SYSTEM
AND SETS THE FORECAST PHILOSOPHY.
   B. TD 20W WILL CONTINUE TRACKING GENERALLY WESTWARD OVER THE NEXT
12 HOURS. AFTERWARDS, IT IS EXPECTED TO BEGIN TURNING POLEWARD AS THE
STEERING STR RECEDES IN RESPONSE TO AN APPROACHING MID-LATITUDE
TROUGH APPROACHING FROM THE NORTHWEST. THE FAVORABLE UPPER LEVEL
CONDITIONS, IN ADDITION TO VERY WARM SEA SURFACE TEMPERATURES IN THE
PHILIPPINE SEA (GREATER THAN 28 CELSIUS) WILL PROMOTE A HIGHER-THAN
NORMAL INTENSIFICATION, PEAKING AT 105 KNOTS BY TAU 72.
   C. AFTER TAU 72, TD 20W IS EXPECTED TO SLOWLY ROUND THE WESTERN
EDGE OF THE STEERING STR AND DRIFT INTO A COL AREA AS A SECONDARY STR
TO THE WEST BUILDS. THIS WILL RESULT IN A POSSIBLE QUASI-STATIONARY
STATE. AFTER TAU 96, THE PRIMARY STR IS EXPECTED TO RE-BUILD AND
NUDGE THE CYCLONE BACK ON A POLEWARD TRACK. INCREASING VERTICAL WIND
SHEAR DURING THIS STAGE WILL GRADUALLY WEAKEN THE SYSTEM. THE
AVAILABLE NUMERICAL GUIDANCE IS IN FAIRLY GOOD AGREEMENT UP TO TAU
72, LENDING GOOD CONFIDENCE TO THAT PORTION OF THE JTWC TRACK
FORECAST THAT IS LAID CLOSE TO THE MODEL CONSENSUS. AFTERWARDS, THERE
IS A SIGNIFICANT SPREAD IN THE CONSENSUS MEMBERS, LENDING LOW
CONFIDENCE TO THE EXTENDED PORTION OF THE FORECAST.//
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