Tropical Storm MAN-YI Advisory mié, 21-11

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 34W (THIRTYFOUR)
WARNING NR 03//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION 34W (THIRTYFOUR), LOCATED APPROXIMATELY 48 NM
NORTH OF NUKUORO, HAS TRACKED WESTWARD AT 09 KNOTS OVER THE PAST SIX
HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY SHOWS A VERY BROAD
CIRCULATION WITH FLARING DEEP CONVECTION. THE INITIAL POSITION IS
PLACED WITH LOW CONFIDENCE NEAR THE DEEPEST CONVECTION. A 192316Z
METOP-A ASCAT IMAGE SHOWS A BROAD CIRCULATION, CONSISTENT WITH A
MONSOON DEPRESSION, WITH 25 KNOTS ON THE PERIPHERY. THE INITIAL
INTENSITY OF 25 KNOTS IS BASED ON THE AFOREMENTIONED ASCAT IMAGE AND
IS CONSISTENT WITH PGTW AND RJTD DVORAK CURRENT INTENSITY ESTIMATES
OF T1.5 (25 KNOTS). THE ENVIRONMENT IS FAVORABLE WITH LOW (5-10
KNOTS) VERTICAL WIND SHEAR, WARM (29-30 CELSIUS) SEA SURFACE
TEMPERATURE, AND GOOD POLEWARD OUTFLOW. TD 34W IS TRACKING ALONG THE
SOUTHERN EDGE OF AN EAST-WEST ORIENTED SUBTROPICAL RIDGE (STR).
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. THROUGH TAU 72, TD 34W WILL TRACK NORTHWESTWARD ALONG THE
SOUTHWESTERN EDGE OF THE STR. A FAVORABLE ENVIRONMENT WILL ALLOW TD
34W TO INTENSIFY, SLOWLY AT FIRST, TO AN INTENSITY OF 95 KNOTS BY
TAU 72. DYNAMIC MODEL GUIDANCE IS IN GOOD AGREEMENT (SPREAD IS 140
NM IF NAVGEM, WHICH IS FOLLOWING A SIMILAR TRACK BUT FASTER, IS
EXCLUDED) THROUGH TAU 72. DESPITE EXCELLENT AGREEMENT IN THE MODEL
GUIDANCE, THERE IS FAIR CONFIDENCE IN THIS PORTION OF THE JTWC
FORECAST TRACK, DUE TO THE UNCERTAINTY IN THE INITIAL POSITION.
   C. AFTER TAU 72, TD 34W WILL ROUND THE STR AXIS AND ACCELERATE
INTO THE MID-LATITUDE WESTERLIES AS IT BEGINS EXTRATROPICAL
TRANSITION (ETT). AFTER TAU 96, VWS IS EXPECTED TO GET VERY HIGH AND
CAUSE THE CYCLONE TO BEGIN WEAKENING CONSIDERABLY AS IT BEGINS ETT.
DYNAMIC MODEL GUIDANCE GENERALLY AGREES THE CYCLONE WILL RECURVE BUT
DIFFER CONSIDERABLY IN THE ALONG-TRACK SPEED AFTER MAKING THE TURN
ONTO A NORTHEASTWARD TRACK. AS A RESULT OF HIGH VARIATION IN ALONG-
TRACK SPEED, THERE IS LOW CONFIDENCE IN THIS PORTION OF THE JTWC
FORECAST TRACK.//
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