Tropical Storm HALONG Advisory Mon Jul 28

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 11W (ELEVEN)
WARNING NR 01//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION (TD) 11W (ELEVEN), LOCATED APPROXIMATELY 304
NM EAST-SOUTHEAST OF ANDERSEN AFB, GUAM, HAS TRACKED WEST-
NORTHWESTWARD AT 04 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED
INFRARED SATELLITE IMAGERY DEPICTS PERSISTENT DEEP CONVECTION ALONG
THE WESTERN EDGE OF AN ILL-DEFINED LOW LEVEL CIRCULATION CENTER
(LLCC) THAT HAS GROWN IN SIZE OVER THE PAST 12 HOURS. A 281016Z
PARTIAL TRMM 37 GHZ MICROWAVE IMAGE REVEALS POORLY DEFINED
CONVECTIVE BANDING ALONG THE NORTHWESTERN QUADRANT WHILE THE LLCC
REMAINS DIFFICULT TO DISCERN. THE INITIAL POSITION IS BASED UPON THE
POSITIONAL FIXES FROM PGTW, KNES AND RJTD WITH POOR CONFIDENCE DUE
TO THE LARGE AMOUNTS OF AMBIGUITY SEEN IN THE AFOREMENTIONED
SATELLITE IMAGERY. THE INITIAL INTENSITY HAS BEEN INCREASED TO
TROPICAL DEPRESSION STRENGTH DUE TO THE INCREASE IN DEEP CONVECTION
WHILE DVORAK INTENSITY ESTIMATES RANGE FROM 25 TO 30 KNOTS. UPPER
LEVEL ANALYSIS, ALONG WITH WATER VAPOR IMAGERY, DEPICTS A CHAOTIC
ENVIRONMENT AS AN UPPER LEVEL TROUGH IS MODIFYING INTO A MORE ZONAL
PATTERN ALONG THE NORTHERN PERIPHERY OF THE SYSTEM. DESPITE THIS
TROUGH PRESSING IN ON THE NORTHERN EDGE OF THE SYSTEM, EQUATORWARD
OUTFLOW HAS PERSISTED ALLOWING FOR CONTINUED GROWTH IN THE
CONVECTION WHILE VERTICAL WIND SHEAR HAS REMAINED RELATIVELY LOW (05
TO 15 KNOTS). THE SYSTEM IS SLOWLY MOVING WEST-NORTHWEST ALONG THE
MID TO LOW-LEVEL REFLECTION OF THE SUBTROPICAL RIDGE (STR) NORTH OF
THE SYSTEM AS IT CONTINUES TO CONSOLIDATE.
3. FORECAST REASONING.
   A. THIS IS THE INITIAL PROGNOSTIC REASONING AND SETS THE FORECAST
PHILOSOPHY.
   B. TD 11W IS FORECAST TO CONTINUE TO THE WEST-NORTHWEST ALONG THE
STR THROUGH THE NEXT 72 HOURS PASSING JUST SOUTH OF TINIAN AS A
TROPICAL STORM. THE STEERING STR IS EXPECTED TO MODIFY DURING THIS
EARLY PORTION OF THE FORECAST AS A MID-LATITUDE TROUGH THAT IS
CURRENTLY SITUATED ACROSS JAPAN TRANSITS WELL NORTH OF THE SYSTEM
DRIVING TD 11W NORTHWESTWARD. SLIGHT INTENSIFICATION IS EXPECTED AS
THE SYSTEM PROCEEDS TOWARDS THE MARIANAS ISLANDS AS GOOD EQUATORWARD
OUTFLOW CONTINUES WITH THE PREVIOUSLY MENTIONED UPPER LEVEL TROUGH
LIMITING POLEWARD OUTFLOW AND PROVIDING MODERATE VWS WHILE ALONG
TRACK SEA SURFACE TEMPERATURES (SSTS) REMAIN FAVORABLE FOR
INTENSIFICATION.
   C. IN THE EXTENDED TAUS, THE SYSTEM IS FORECAST TO TRACK
GENERALLY NORTHWEST ALONG THE STR TO THE NORTH. CONTINUED GRADUAL
INTENSIFICATION TO TYPHOON STRENGTH IS EXPECTED AS THE UPPER LEVEL
ENVIRONMENT REMAINS MARGINAL AND SSTS ARE CONDUCIVE. LIMITED MODEL
GUIDANCE TRACK GENERALLY SUPPORTS THE FORECAST TRACK ALTHOUGH AT
GREATLY VARIED INTENSITIES. GFS, THE GFS ENSEMBLE, AND HWRF SUPPORT
A CONTINUED WEST-NORTHWEST TRACK AND QUICKLY INTENSIFY THE SYSTEM
WHILE EGRR SHOWS THE SAME TRACK AT A SLOWER INTENSIFICATION RATE.
NAVGEM DISPLAYS AN ALTERNATE SCENARIO AS IT QUICKLY WEAKENS THE
SYSTEM AS IT BRINGS THE UPPER LEVEL TROUGH FURTHER SOUTH ALLOWING
THE SUBSIDENCE ALOFT TO QUICKLY DISSIPATE ALL CONVECTION. DUE TO THE
CURRENT CLOSE PROXIMITY TO THE TROUGH, THIS SCENARIO MAY HAVE SOME
VALIDITY. OVERALL, THERE IS LOW CONFIDENCE IN THE FORECAST TRACK.//
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