WDPN31 PGTW 280300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 03W (THREE)
WARNING NR 01//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL DEPRESSION (TD) 03W (THREE), LOCATED APPROXIMATELY 308
NM SOUTH-SOUTHEAST OF ANDERSEN AFB, GUAM, HAS TRACKED WEST-
NORTHWESTWARD AT 03 KNOTS OVER THE PAST SIX HOURS. ANIMATED
MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS FLARING CONVECTION
THAT IS STARTING TO BUILD OVER AN ILL-DEFINED AND BROAD LOW LEVEL
CIRCULATION CENTER (LLCC). A 271950Z SSMIS 37 GHZ MICROWAVE IMAGE
REVEALS A SLIGHT INCREASE IN THE CONSOLIDATION OF THE LOW-LEVEL
STRUCTURE WHILE THE BULK OF THE CONVECTION CONTINUES TO BE CONTAINED
TO THE NORTH WHILE THERE HAS BEEN AN INCREASE IN CONVECTION ALONG
THE SOUTHWESTERN PERIPHERY THAT HAS STARTED TO WRAP INTO THE LLCC.
THE INITIAL POSITION IS BASED UPON THE MSI ANIMATION WITH LOW
CONFIDENCE AS THE FLARING CONVECTION IS OBSCURING THE LLCC AND
AGENCY POSITION FIXES ARE WIDELY SPREAD. THE INITIAL INTENSITY IS
ASSESSED AT 25 KNOTS BASED UPON THE BROAD ORGANIZATION OF THE SYSTEM
AND DVORAK INTENSITY ESTIMATES OF THE SAME VALUE FROM PGTW AND KNES.
UPPER-LEVEL ANALYSIS REVEALS A MARGINAL ENVIRONMENT AS VIGOROUS
POLEWARD OUTFLOW IS BEING OFFSET BY MODERATE (15 TO 20 KNOTS)
VERTICAL WIND SHEAR (VWS). TD 03W IS CURRENTLY IN A WEAK STEERING
ENVIRONMENT AND IS TRACKING SLIGHTLY ERRATIC AS THE SYSTEM IS
BETWEEN TWO LOW- TO MID-LEVEL SUBTROPICAL RIDGES (STR) TO THE
NORTHEAST AND NORTHWEST.
3. FORECAST REASONING.
A. THIS IS THE INITIAL PROGNOSTIC REASONING AND SETS THE FORECAST
PHILOSOPHY.
B. TD 03W IS EXPECTED TO STAY IN THIS WEAK STEERING ENVIRONMENT
BETWEEN THE TWO STEERING RIDGES FOR THE NEXT TWO DAYS WITH A HIGH
POSSIBILITY OF QUASI-STATIONARY AND ERRATIC MOTION. AFTER TAU 48,
THE STR TO THE NORTHEAST IS EXPECTED TO AMPLIFY AND BECOME THE
DOMINANT STEERING INFLUENCE. THIS WILL DRIVE TD 03W ON A POLEWARD
TRACK AND WILL INCREASE TRACK SPEEDS. THE SYSTEM IS EXPECTED TO
SLOWLY INTENSIFY THROUGH THE NEXT 72 HOURS, REACHING A PEAK OF 50
KNOTS, AS MODELS INDICATE A SLIGHT RELAXATION OF THE VWS AS TD 03W
GAINS LATITUDE. NUMERIC MODEL GUIDANCE IS IN FAIRLY GOOD AGREEMENT
WITH THE WEAK STEERING ENVIRONMENT AS THE TRACKERS KEEP THE SYSTEM
VERY SLOW MOVING THROUGH THE NEXT 48 HOURS ALTHOUGH WITH VARYING
TRAJECTORIES DUE TO THE POORLY DEFINED STEERING.
C. IN THE EXTENDED PERIOD, TD 03W IS EXPECTED TO FURTHER
ACCELERATE POLEWARD AS IT TRACKS ALONG THE PERIPHERY OF THE STR AND
WILL BEGIN TO TAKE A NORTHEASTWARD TRACK AS IT APPROACHES THE MID-
LATITUDE WESTERLIES BY TAU 120. THE SYSTEM IS EXPECTED TO WEAKEN
AFTER TAU 72 AS INCREASING VWS FROM THE WESTERLIES WILL START TO
HAMPER THE SYSTEM. EXTRA-TROPICAL TRANSITION IS FORECAST TO BEGIN AT
TAU 120 AS THE SYSTEM APPROACHES THE WESTERLIES AND SEA SURFACE
TEMPERATURES START TO DECREASE. NUMERIC MODEL GUIDANCE REMAINS IN
GOOD AGREEMENT WITH THE OVERALL FORECAST SCENARIO IN THE EXTENDED
TAUS ALTHOUGH MODELS ARE WIDELY SPREAD DUE TO THE WEAK STEERING IN
THE EARLY PORTION OF THE FORECAST. THE JTWC FORECAST TRACK IS
POSITIONED CLOSE TO MULTI-MODEL CONSENSUS DUE TO THIS SPREAD.
OVERALL, CONSIDERING THE WEAK STEERING ENVIRONMENT IN THE EARLY TAUS
AND THE POOR CONFIDENCE IN THE INITIAL POSITION, THERE IS LOW
CONFIDENCE IN THE FORECAST.//
NNNN
Meow wrote:euro6208 wrote:3rd Tropical Cyclone of the season!
So it is expected to be a harmless system.
It's the first warning and models are everywhere so there is low confidence in the forecast. It doesn't take winds to cause harm, the rain will be the issue here...
