Tropical Storm NOUL Advisory Sun May 03

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 06W (NOUL) WARNING NR
05//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 06W (NOUL), LOCATED APPROXIMATELY 131 NM EAST
OF YAP, HAS TRACKED WEST-NORTHWESTWARD AT 04 KNOTS OVER THE PAST SIX
HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS CURVED
BANDING WRAPPING INTO A PARTIALLY EXPOSED LOW LEVEL CIRCULATION
CENTER , WITH DEEP CONVECTION IN THE NORTHERN AND WESTERN QUADRANTS.
THE CURRENT POSITION IS BASED ON MSI AND FIXES FROM PGTW AND RJTD,
AND IS FURTHER SUPPORTED BY A 032210Z SSMIS 37 GHZ MICROWAVE PASS
WITH HIGH CONFIDENCE. THE INITIAL INTENSITY IS ASSESSED AT 35 KNOTS
BASED ON DVORAK CURRENT INTENSITY ESTIMATES OF T2.5 FROM ALL
AGENCIES. THE FORWARD MOTION HAS SLOWED IN RESPONSE TO A
WEAKNESS IN THE SUBTROPICAL RIDGE (STR) TO THE NORTH. UPPER LEVEL
ANALYSIS INDICATES THE ENVIRONMENT HAS BECOME SLIGHTLY LESS
FAVORABLE, WITH THE EFFECTS OF INCREASED (15 KNOTS) SOUTHEASTERLY
VERTICAL WIND SHEAR (VWS) EVIDENT IN THE MSI. POLEWARD OUTFLOW HAS
ALSO WANED SLIGHTLY. SEA SURFACE TEMPERATURES REMAIN FAVORABLE AT 28-
29 DEGREES CELSIUS.
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM
THE PREVIOUS WARNING.
   B. TS 06W IS EXPECTED TO SLOWLY TRACK WESTWARD OVER THE NEXT
36-48 HOURS WHILE THE WEAKENED STR TO THE NORTH GRADUALLY REBUILDS.
BY TAU 48, FORWARD MOTION SHOULD INCREASE AND RESUME A WEST-
NORTHWESTWARD TRACK ALONG THE SOUTHERN PERIPHERY OF THE STEERING
RIDGE. VWS AND UPPER-LEVEL OUTFLOW ARE EXPECTED TO BE GENERALLY
FAVORABLE DURING THIS PORTION OF THE FORECAST, ENABLING NOUL TO
STEADILY INTENSIFY AT A NEAR CLIMATOLOGICAL RATE. UNCERTAINLY AMONG
THE NUMERICAL GUIDANCE AIDS IS HIGH, WITH TRACK SOLUTIONS HIGHLY
DEPENDENT ON THE STRENGTH OF THE STR DEPICTED BY THE MODEL. GFDN,
COTC, NVGM, AND ECMWF ALL DRIVE THE SYSTEM EQUATORWARD OVER THE NEXT
36 HOURS, WHILE REMAINING MODELS MAINTAIN A NORTHWESTWARD TRACK.
DUE TO THE LARGE MODEL SPREAD, THE NEAR-TERM JTWC FORECAST IS PLACED
SLIGHTLY NORTH OF THE MULTI-MODEL CONSENSUS WITH LOW CONFIDENCE.
   C. IN THE EXTENDED TAUS, TS 06W WILL TRACK STEADILY NORTHWESTWARD
UNDER THE STEERING INFLUENCE OF A BUILDING STR. THE SYSTEM SHOULD
CONTINUE TO INTENSIFY GIVEN FAVORABLE ENVIRONMENTAL INFLUENCES.
NUMERIC MODEL GUIDANCE IS BIFURCATED, AS DIFFERENCES IN MODEL
DEPICTION OF THE STR RESULT IN EITHER A STRAIGHT-RUNNING OR A
RECURVING TRACK. OVER THE PAST CYCLE, THE HWRF SOLUTION CHANGED
DRASTICALLY, CALLING FOR A PEAK OF ONLY 55 KNOTS AND PRONOUCED
SOUTHWARD SHIFT IN TRACK. THE GFS AND GEFS MAINTAIN A STRONGER
VORTEX THAT STARTS TO ROUND THE STR AT THE END OF THE FORECAST
PERIOD. THE FORECAST IS PLACED CLOSE TO THE CONSENSUS MEAN TRACK,
AND ADJUSTED SLIGHTLY TO ACCOUNT FOR EXTREME SOUTHERN OUTLIERS (GFDN
AND COTC). BASED ON THE LARGE GUIDANCE SPREAD, CONFIDENCE IN THE
JTWC 96 AND 120 HOUR FORECAST POSITIONS IS LOW.//
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