Tropical Storm TRAMI Advisory Thu Sep 27

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 28W (TRAMI) WARNING NR 26//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON 28W (TRAMI), LOCATED APPROXIMATELY 302 NM SOUTH-
SOUTHEAST OF KADENA AB, HAS TRACKED NORTH-NORTHWESTWARD AT 02 KNOTS
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL (MSI) SATELLITE
IMAGERY SHOWS TY 28W MAINTAINS A WIDE EYE, AND IS MAINTAINING DEEP
CONVECTION IN THE EYEWALL. THE INITIAL POSITION IS PLACED WITH HIGH
CONFIDENCE BASED ON THE WIDE EYE IN THE MSI LOOP. THE INITIAL
INTENSITY IS MAINTAINED AT 90 KNOTS, IN AGREEMENT WITH THE PGTW AND
KNES DVORAK CURRENT INTENSITY (CI) ESTIMATES OF T5.0 (90 KTS), AND
BELOW THE RJTD ESTIMATE OF T5.5 (102 KTS), AND SLIGHTLY BELOW A
262000Z SATCON ESTIMATE OF 93 KNOTS. ENVIRONMENTAL ANALYSIS SHOWS
TY 28W IS EXPERIENCING FAVORABLE VERTICAL WIND SHEAR (5 TO 10
KNOTS) ALONG WITH GOOD RADIAL OUTFLOW, WHICH IS BEING ENHANCED BY A
PASSING MIDLATITUDE TROUGH TO THE NORTH. SEA SURFACE TEMPERATURES
REMAIN FAVORABLE NEAR 28 DEGREES CELSIUS, ALTHOUGH THE SLOW MOTION
OF TY 28W IS ALLOWING FOR UPWELLING, WHICH IS REDUCING THE
AVAILABLE OCEAN HEAT CONTENT (OHC) FOR THE SYSTEM, LEADING IT TO
MAINTAIN ITS INTENSITY IN THE MIDST OF AN OTHERWISE FAVORABLE
ENVIRONMENT. TY 28W IS ALMOST QUASI-STATIONARY IN A WEAK STEERING
ENVIRONMENT WHILE IN BETWEEN A SUBTROPICAL RIDGE (STR) LOCATED TO
THE WEST AND A SECOND STR LOCATED TO THE EAST.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TY 28W IS FORECAST TO TRACK SLOWLY NORTH TO NORTHWESTWARD IN
THE AMBIGUOUS STEERING ENVIRONMENT WHILE MAINTAINING ITS INTENSITY,
CAUGHT IN A BALANCE BETWEEN FAVORABLE OUTFLOW AND LOW VWS, AND THE
UNFAVORABLE LOWER OHC. AFTER TAU 12, THE STR TO THE EAST WILL
BUILD, BECOME THE DOMINANT STEERING FEATURE, AND ALLOW TY 28W TO
INCREASE FORWARD MOTION AND TRACK NORTHWESTWARD THROUGH TAU 36. BY
TAU 36, TY 28W WILL ENCOUNTER AN AREA OF WARM (28-30 C) SSTS THAT
IT HAS NOT ALREADY CHURNED UP, WHICH WILL ALLOW FOR A PERIOD OF RE-
INTENSIFICATION, REACHING 110 KTS BY TAU 72. MODELS ARE IN
AGREEMENT THAT TY 28W WILL TRACK NORTHWESTWARD IN THE NEAR-TERM,
WITH NAVGEM A NOTABLE OUTLIER TO THE WEST DUE TO IT BUILDING IN A
MORE ROBUST STR TO THE EAST. AFTER TAU 48, TY 28W WILL HAVE ROUNDED
THE RIDGE AND WILL BEGIN ACCELERATING TO THE NORTHEAST. A
MIDLATITUDE TROUGH MOVING INTO THE YELLOW SEA REGION WILL ALSO
ENHANCE OUTFLOW, CONTRIBUTING TO THE RE-INTENSIFICATION TREND. THE
JTWC FORECAST TRACK IS PLACED CLOSE TO THE MULTI-MODEL CONSENSUS.
DUE TO THE 368 NM MODEL SPREAD AT TAU 72, THERE IS LOW CONFIDENCE
IN THIS PORTION
OF THE JTWC FORECAST TRACK.
   C. AFTER TAU 72, TY 28W WILL CONTINUE TO ACCELERATE TO THE
NORTHEAST, PULLED BY THE MIDLATITUDE WESTERLIES AND AFOREMENTIONED
PASSING TROUGH. INCREASED VERTICAL WIND SHEAR, COOLER SEA SURFACE
TEMPERATURES, AND EVENTUAL LAND INTERACTION WILL WEAKEN THE SYSTEM
AS IT TRACKS NORTHEASTWARD. TY 28W WILL BE EMBEDDED IN THE
BAROCLINIC ZONE AND BEGIN EXTRA-TROPICAL TRANSITION (ETT) BY TAU
96, AND WILL COMPLETE ETT BY TAU 120. THE JTWC FORECAST TRACK IS
PLACED NEAR THE MULTI-MODEL CONSENSUS. MODEL GUIDANCE IS IN GOOD
AGREEMENT THAT TY 28W WILL TRACK NORTHEASTWARD, BUT MODELS DIFFER
ON THE TRACK SPEED. THEREFORE, THERE IS LOW CONFIDENCE IN THIS
PORTION OF THE JTWC FORECAST TRACK.//
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