Tropical Storm FOURTEEN Advisory Wed Aug 24

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 14W (FOURTEEN)
WARNING NR 01//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION (TD) 14W (FOURTEEN), LOCATED APPROXIMATELY 41
NM EAST OF ANDERSEN AFB, GUAM, HAS TRACKED NORTHWARD AT 15 KNOTS
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY
INDICATES A PARTIALLY-EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC)
WITH PERSISTENT DEEP CONVECTION OVER THE SOUTHERN SEMI-CIRCLE AND
FLARING, ISOLATED DEEP CONVECTION OVER THE NORTHERN SEMI-CIRCLE. A
230542Z SSMIS 91GHZ IMAGE AND RADAR IMAGERY FROM GUAM SHOW MULTIPLE
CONVECTIVE BANDS WRAPPING INTO A DEFINED CENTER, WHICH PROVIDES GOOD
CONFIDENCE TO THE CURRENT POSITION. UPPER-LEVEL ANALYSIS INDICATES A
MARGINAL ENVIRONMENT WITH MODERATE TO STRONG NORTHERLY VERTICAL WIND
SHEAR (VWS) HINDERING CONVECTIVE DEVELOPMENT OVER THE NORTHERN SEMI-
CIRCLE. THE INITIAL INTENSITY IS ASSESSED AT 30 KNOTS BASED ON
DVORAK INTENSITY ESTIMATES OF T2.0 (30 KNOTS) FROM PGTW AND KNES. AS
DEPICTED IN RECENT ASCAT IMAGERY, THERE IS AN AREA OF EXTENSIVE GALE-
FORCE WINDS LOCATED OVER THE SOUTHERN AND SOUTHEASTERN QUADRANTS.
RECENT SURFACE OBSERVATIONS FROM SAIPAN SHOW A SPIKE IN WINDS TO 31
KNOTS SUSTAINED, THEREFORE, THE SYSTEM INTENSITY WILL BE RE-ASSESSED
FOR TROPICAL STORM STRENGTH. TD 14W IS TRACKING QUICKLY POLEWARD
ALONG THE WESTERN PERIPHERY OF A STRONG LOW- TO MID-LEVEL STEERING
RIDGE TO THE EAST OF THE SYSTEM.
3. FORECAST REASONING.
   A. THIS IS THE FIRST PROGNOSTIC REASONING MESSAGE AND SETS THE
FORECAST PHILOSOPHY.
   B. TD 14W WILL CONTINUE TO ACCELERATE NORTHWARD THROUGH TAU 36
WHILE SLOWLY INTENSIFYING UNDER MARGINAL UPPER-LEVEL CONDITIONS.
AVAILABLE MODEL TRACKERS ARE LIMITED BUT ARE IN GOOD AGREEMENT AS
THE SYNOPTIC STEERING PATTERN IS CLEAR CUT. THE ONLY EXCEPTION IS
GFS, WHICH SPINS UP ANOTHER SYSTEM FROM TD 14W AND ROTATES THE TWO
SYSTEMS UNTIL THEY COMBINE INTO ONE STRONGER SYSTEM; THIS SCENARIO
IS UNLIKELY AND RESULTS IN A SHARP EAST-NORTHEASWTARD TRACK AFTER
TAU 36. TD 14W APPEARS TO HAVE A BRIEF WINDOW, BETWEEN TAU 36 AND
72, WHERE POLEWARD OUTFLOW IMPROVES IN ASSOCIATION WITH AN UPPER-
LEVEL TROUGH TO THE NORTH. CONSEQUENTLY, PEAK INTENSITY OF 45 KNOTS
IS FORECAST DURING THIS PERIOD.
   C. IN THE EXTENDED TAUS, TD 14W WILL SLOW AND BEGIN TO TRACK
NORTHWESTWARD TO WEST-NORTHWESTWARD UNDER THE STEERING INFLUENCE OF
THE SUBTROPICAL RIDGE TO THE NORTH. TD 14W IS EXPECTED TO WEAKEN,
HOWEVER, DUE TO COOLER SST (LESS THAN 26C) AND INCREASING VWS
ASSOCIATED WITH AN UPPER-LEVEL TROUGH OVER THE SYSTEM. OVERALL,
THERE IS LOW CONFIDENCE IN THE JTWC FORECAST TRACK DUE TO
UNCERTAINTY IN THE EXTENDED TAUS.//
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