Tropical Storm NOUL Advisory Mon May 04

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 06W WARNING NR 02//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION (TD) 06W (SIX), LOCATED APPROXIMATELY 212 NM
EAST-SOUTHEAST OF YAP, HAS TRACKED NORTHWESTWARD AT 05 KNOTS OVER THE
PAST SIX HOURS. THE PREVIOUS POSITION HAS BEEN ADJUSTED EASTWARD
SLIGHTLY BASED ON NEWLY-AVAILABLE SATELLITE DATA. THE CURRENT
POSITION IS BASED ON A RECENT PGTW SATELLITE POSITION FIX AND
ANIMATED MULTISPECTRAL SATELLITE IMAGERY. THE CURRENT INTENSITY OF
25 KNOTS IS CONSISTENT WITH DVORAK SATELLITE INTENSITY ESTIMATES
FROM MULTIPLE REPORTING AGENCIES. FRAGMENTED DEEP CONVECTION IS
CONFINED PRIMARILY TO THE NORTHERN PORTION OF THE PARTIALLY-EXPOSED
LOW-LEVEL CIRCULATION CENTER (LLCC). 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. STORM MOTION HAS
DECREASED IN THE PAST 12 HOURS IN RESPONSE TO A DEVELOPING WEAKNESS
IN THE SUBTROPICAL STEERING RIDGE TO THE NORTH OF THE SYSTEM.
3. FORECAST REASONING.
   A. FORECAST TRACK SPEEDS HAVE DECREASED SINCE THE PREVIOUS
WARNING IN ANTICIPATION OF A WEAKENED STEERING ENVIRONMENT DURING
NEXT 48 TO 72 HOURS. MEDIUM TO EXTENDED RANGE FORECAST INTENSITIES
HAVE INCREASED BASED ON FAVORABLE UPPER-LEVEL SUPPORT.
   B. TD 06W IS EXPECTED TO TRACK SLOWLY WEST-NORTHWESTWARD OVER THE
NEXT 48 TO 72 HOURS AS IT ENCOUNTERS A WEAKNESS IN THE SUBTROPICAL
RIDGE. THEREAFTER, A MID-LATITUDE TROUGH INDUCING THE WEAKNESS WILL
MOVE EASTWARD, ALLOWING THE SUBTROPICAL RIDGE TO REBUILD AND STEER
THE SYSTEM MORE RAPIDLY INTO THE PHILIPPINE SEA. VERTICAL WIND SHEAR
SHOULD REMAIN LOW AND UPPER-LEVEL OUTFLOW IS EXPECTED TO IMPROVE,
ENABLING TD 06W TO STEADILY INTENSIFY AFTER AN INITIAL PERIOD OF
CONSOLIDATION DURING THE NEXT 12 HOURS. NUMERIC MODELS ARE GENERALLY
IN GOOD AGREEMENT REGARDING TRACK DIRECTION BUT LESS AGREEMENT
REGARDING TRACK SPEED DURING THE FIRST 72 HOURS OF THE FORECAST.
GIVEN HIGH UNCERTAINTY ASSOCIATED WITH THE DEVELOPING WEAKNESS IN
THE STEERING RIDGE, THE LOW-CONFIDENCE JTWC FORECAST IS PLACED NEAR
THE MULTI-MODEL CONSENSUS.
   C. IN THE EXTENDED TAUS, TD 06W WILL TRACK STEADILY WEST-
NORTHWESTWARD UNDER THE STEERING INFLUENCE OF THE REORIENTED
SUBTROPICAL RIDGE. THE SYSTEM SHOULD CONTINUE TO INTENSIFY AS
ENVIRONMENTAL INFLUENCES REMAIN FAVORABLE. NUMERIC MODEL GUIDANCE IS
IN BETTER 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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