meteo





Invest 97W is now TD BAILU(12W). Intensifying, landfall over Taiwan shortly after 72h


Warning 1/JTWC


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WESTERN NORTH PACIFIC

TD BAILU(12W)
As of 06:00 UTC Aug 21, 2019:
Location: 15.2°N 131.9°E
Maximum Winds: 25 kt
Minimum Central Pressure: 1001 mb

WDPN31 PGTW 210900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 12W (BAILU) WARNING
NR 01//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION (TD) 12W (BAILU), LOCATED APPROXIMATELY 716 NM
SOUTH-SOUTHEAST OF KADENA AB, HAS TRACKED NORTHWESTWARD AT 07 KNOTS
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY
SHOWS THAT TD 12W HAS A BROAD AREA OF CONVECTION WHICH IS CONTINUING
TO CONSOLIDATE AROUND THE LOW LEVEL CIRCULATION CENTER (LLCC). THE
INITIAL POSITION IS PLACED WITH LOW CONFIDENCE BASED ON THE BROAD
NATURE OF THE SYSTEM. THE POSITION IS BASED ON A PARTIAL 210503Z
AMSR2 89GHZ MICROWAVE IMAGE WHICH SHOWS DEEP CONVECTION TO THE WEST
OF THE LLCC WITH WEAKER BANDING CONVECTION TO THE NORTHWEST AND NORTH
OF THE LLCC. THE INITIAL INTENSITY OF 25 KNOTS IS BASED ON A DVORAK
CURRENT INTENSITY (CI) ESTIMATE OF T1.0 (25 KNOTS) FROM PGTW AND
HEDGED SLIGHTLY BELOW THE CI OF T2.0 (30 KNOTS) FROM RJTD.
ENVIRONMENTAL ANALYSIS SHOWS TD 12W IS EXPERIENCING FAVORABLE
VERTICAL WIND SHEAR (5 TO 15 KNOTS). TD 12W HAS A STRONG EQUATORWARD
OUTFLOW CHANNEL AND A DEVELOPING POLEWARD OUTFLOW CHANNEL WITH A
TROPICAL UPPER TROPOSPHERIC TROUGH (TUTT) CELL BEGINNING TO ENHANCE
THE OUTFLOW. SEA SURFACE TEMPERATURES ARE FAVORABLE FOR DEVELOPMENT,
NEAR 30 DEGREES CELSIUS. TD 12W IS TRACKING NORTHWESTWARD WHILE UNDER
THE INFLUENCE OF A SUBTROPICAL RIDGE (STR) LOCATED TO THE NORTHEAST.
3. FORECAST REASONING.
   A. THIS IS THE INITIAL PROGNOSTIC REASONING MESSAGE AND SETS THE
FORECAST PHILOSOPHY FOR THIS SYSTEM.
   B. IN THE SHORT TERM, TD 12W WILL CONTINUE TO EXPERIENCE FAVORABLE
VERTICAL WIND SHEAR AND REMAIN OVER WARM SEA SURFACE TEMPERATURES,
WHICH WILL ALLOW FOR A STEADY INCREASE IN INTENSITY. THE
AFOREMENTIONED TUTT CELL WILL CONTINUE TO ENHANCE UPPER LEVEL OUTFLOW
IN THE SHORT TERM AND ALSO ALLOW FOR INTENSIFICATION. THE STR TO THE
NORTHEAST WILL REMAIN IN PLACE THROUGH TAU 72 AND ALLOW TD 12W TO
TRACK NORTHWESTWARD. DYNAMIC MODEL GUIDANCE IS IN GOOD AGREEMENT,
HOWEVER, DUE TO THE HIGH UNCERTAINTY IN THE INITIAL POSITION THERE IS
LOW CONFIDENCE IN THIS PORTION OF THE JTWC FORECAST TRACK.
   C. AFTER TAU 72, TD 12W WILL CONTINUE TO TRACK NORTHWESTWARD WHILE
UNDER THE INFLUENCE OF THE STR. SHORTLY AFTER TAU 72, TD 12W WILL
MAKE LANDFALL IN CENTRAL TAIWAN WHICH WILL LEAD TO A WEAKENING TREND.
BY TAU 96, AN APPROACHING WEST TO EAST MOVING SHORTWAVE TROUGH WILL
TEMPORARILY WEAKEN THE STR AND ALLOW TD 12W TO TRACK SLIGHTLY MORE
NORTHWARD. LAND INTERACTION WITH CHINA WILL CAUSE TD 12W TO QUICKLY
WEAKEN AFTER TAU 96 AND DISSIPATE BY TAU 120. DYNAMIC MODEL GUIDANCE
IS IN POOR AGREEMENT DURING THIS PORTION OF THE TRACK. MODEL GUIDANCE
HAS A SPREAD OF 860NM BY TAU 120. DUE TO THE MODEL SPREAD AND THE
HIGH UNCERTAINTY IN THE INITIAL POSITION THERE IS LOW CONFIDENCE IN
THIS PORTION OF THE JTWC FORECAST TRACK.//
NNNN




TRACK AND INTENSITY GUIDANCE
TRACK AND INTENSITY GUIDANCE
Rédigé par PATRICK HOAREAU le Mercredi 21 Août 2019 à 15:50