Tropical Storm YUTU Advisory Sun Oct 28

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 31W (YUTU) WARNING NR
24//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   SUPER TYPHOON (STY) 31W (YUTU), LOCATED APPROXIMATELY 571 NM
NORTH-NORTHWEST OF YAP, HAS TRACKED WESTWARD AT 13 KNOTS OVER THE
PAST SIX HOURS. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE
BASED ON ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) WHICH SHOWS
A ROUND 28-NM EYE, SURROUNDED BY SYMMETRIC DEEP CONVECTION. THE
MICROWAVE EYE FEATURE IN A 270537Z SSMI 37 GHZ CHANNEL IS SLIGHTLY
SOUTH OF THE EYE FEATURE IN THE 85 GHZ CHANNEL, SUGGESTING THE
CYCLONE IS TILTED SLIGHTLY TO THE NORTH WITH HEIGHT. THE INITIAL
INTENSITY OF 135 KNOTS IS AVERAGED BETWEEN MULTI-AGENCY DVORAK
CURRENT INTENSITY ESTIMATES OF T6.5-T7.0 (127-140 KNOTS). THE
ENVIRONMENT IS MARGINALLY FAVORABLE WITH GOOD EQUATORWARD OUTFLOW,
EXCELLENT POLEWARD OUTFLOW, AND WARM (28-29 CELSIUS) SEA SURFACE
TEMPERATURE BEING OFFSET BY HIGH (25 KNOTS) VERTICAL WIND SHEAR
(VWS). THE CYCLONE IS TRACKING ALONG THE SOUTHERN PERIPHERY OF AN
EAST-WEST ORIENTED SUBTROPICAL RIDGE (STR) TO THE NORTH WITH AN
EASTWARD MOVING MID-LATITUDE TROUGH CREATING A WEAKNESS IN THE STR
TO THE NORTH OF STY 31W.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. THROUGH TAU 72, STY 31W IS FORECAST TO CONTINUE TRACKING
WESTWARD TO WEST-SOUTHWESTWARD AND GRADUALLY WEAKEN THANKS TO
DIMINISHING OUTFLOW AS THE TROPICAL CYCLONE AND MID-LATITUDE TROUGH
TO THE NORTH MOVE FURTHER APART. BY TAU 72, STY 31W IS EXPECTED TO
MAKE LANDFALL ON LUZON. MOST OF THE NUMERICAL MODEL GUIDANCE IS IN
GOOD AGREEMENT (177 NM SPREAD) WITH THE JTWC TRACK FORECAST,
HOWEVER, THE SPREAD INCREASES TO ABOUT 300 NM WHEN CONSIDERING THE
NORTHERN (COAMPS-GFS) AND SOUTHERN (JGSM) OUTLIERS. BASED ON THE
SPREAD, THERE IS MODERATE UNCERTAINTY IN THE JTWC TRACK FORECAST.
   C. BEYOND TAU 72, AN APPROACHING MID-LATITUDE TROUGH WILL CREATE
A WEAKNESS IN THE STR AND ALLOW STY 31W TO BEGIN RECURVING
NORTHWARD. ENVIRONMENTAL CONDITIONS WILL BE GENERALLY UNFAVORABLE
FOR THIS PORTION OF THE FORECAST AND THAT, COUPLED WITH LAND
INTERACTION, IS EXPECTED TO WEAKEN STY 31W. THERE IS A CHANCE THAT
ENHANCED POLEWARD OUTFLOW AS IT ROUNDS THE STR MAY ALLOW FOR SLIGHT
INTENSIFICATION BEFORE HIGH VWS CAUSES STY 31W TO WEAKEN. SPREAD IN
THE NUMERICAL MODELS IS ALMOST 1000 NM BY TAU 120, ALTHOUGH THE
SPREAD IS REDUCED TO 230 NM WHEN COAMPS-GFS AND JGSM ARE REMOVED.
BASED ON THE RELATIVELY SMALL SPREAD IN THE BULK OF THE GUIDANCE,
THERE IS MODERATE UNCERTAINTY IN THE EXTENDED PORTION OF THE JTWC
FORECAST TRACK.//
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