Tropical Storm NOUL Advisory Sun May 03

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 06W WARNING NR 03//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION (TD) 06W (SIX), LOCATED APPROXIMATELY 192 NM
EAST OF YAP, HAS TRACKED NORTH-NORTHWESTWARD AT 05 KNOTS OVER THE
PAST SIX HOURS. THE CURRENT POSITION IS BASED ON A RECENT PGTW FIX
ON INFRARED SATELLITE IMAGERY. THE INTENSITY OF 30 KNOTS IS BASED ON
DVORAK SATELLITE INTENSITY ESTIMATES OF T=2.0 FROM PGTW AND KNES. TD
06W IS MOVING SLOWLY POLEWARD INTO A WEAKNESS IN THE SUBTROPICAL
STEERING RIDGE INDUCED BY A MID-LATITUDE TROUGH PASSING TO THE
NORTH. THE LLCC LIES EQUATORWARD OF AN UPPER-LEVEL RIDGE AXIS, IN AN
AREA OF LOW TO MODERATE EASTERLY VERTICAL WIND SHEAR AND FAVORABLE
POLEWARD OUTFLOW. DEEP CONVECTION HAS INCREASED DURING THE PAST SIX
HOURS, PARTICULARLY OVER THE NORTHERN PORTION OF THE LOW LEVEL
CIRCULATION CENTER (LLCC). A DEVELOPING UPPER-LEVEL POLEWARD OUTFLOW
CHANNEL IS SUPPORTING THIS CONVECTIVE DEVELOPMENT.
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM
THE PREVIOUS WARNING.
   B. TD 06W IS EXPECTED TO TRACK SLOWLY WEST-NORTHWESTWARD DURING
THE UPCOMING 48 TO 72 HOUR PERIOD UNDER THE STEERING INFLUENCE OF
WEAKENED SUBTROPICAL RIDGING TO THE NORTH. THEREAFTER, THE MID-
LATITUDE TROUGH INDUCING THE RIDGE WEAKNESS WILL MOVE EASTWARD,
ALLOWING THE SUBTROPICAL RIDGE TO REBUILD AND STEER TD 06W MORE
RAPIDLY WEST-NORTHWESTWARD INTO THE PHILIPPINE SEA. VERTICAL WIND
SHEAR AND UPPER-LEVEL OUTFLOW ARE EXPECTED TO REMAIN FAVORABLE,
ENABLING TD 06W TO STEADILY INTENSIFY AFTER AN INITIAL PERIOD OF
CONSOLIDATION OVER THE NEXT 6 TO 12 HOURS. NUMERIC MODELS REMAIN IN
GOOD GENERAL AGREEMENT REGARDING TRACK DIRECTION, BUT LESS AGREEMENT
REGARDING TRACK SPEED DURING THE FIRST 72 HOURS OF THE FORECAST.
GIVEN UNCERTAINTY ASSOCIATED WITH THE EVOLUTION OF THE OBSERVED
WEAKNESS IN THE STEERING RIDGE, THE NEAR-TERM JTWC FORECAST IS
PLACED NEAR THE MULTI-MODEL CONSENSUS WITH LOW CONFIDENCE.
   C. IN THE EXTENDED TAUS, TD 06W WILL TRACK STEADILY WEST-
NORTHWESTWARD UNDER THE STEERING INFLUENCE OF A BUILDING SUBTROPICAL
RIDGE. THE SYSTEM SHOULD CONTINUE TO INTENSIFY AS ENVIRONMENTAL
INFLUENCES REMAIN FAVORABLE. NUMERIC MODEL GUIDANCE IS IN FAIR
AGREEMENT REGARDING TRACK DIRECTION AND SPEED IN THE EXTENDED TERM,
LENDING HIGHER CONFIDENCE TO THE JTWC 96 AND 120 HOUR FORECAST
POSITIONS.//
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