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wdpn31 pgtw 240300
msgid/genadmin/joint typhoon wrncen Pearl Harbor hi//
subj/prognostic reasoning for tropical depression 20w (twentytwo) 
warning nr 02//
1. For meteorologists.
2. 6 hour summary and analysis.
Tropical depression 22w (twentytwo), located approximately 255 nm
south-southwest of Hong Kong, has tracked westward at 14 knots
over the past six hours. Animated multispectral satellite imagery 
depicts a partially exposed low level circulation center (LLCC) with 
flaring central convection being sheared to the southwest. The 
initial position is placed with high confidence based on the exposed 
LLCC and a low reflectivity feature observed in a 232311z 91ghz 
ssmis image. Multi-agency Dvorak estimates range from t1.5 to t2.0 
(25 to 30 knots) and local ship observations are reporting winds in 
excess of 25 knots, which is the basis for the initial 30 knot 
intensity. Upper-level analysis indicates fairly strong easterly 
flow from a well established Northern Ridge. While the system is 
traveling in phase with the upper-level winds, TD 22w has slowed 
down over the last six hours resulting in a notable increase in wind 
shear. SSTs in the region are also favorable near 30 celsius.  
Currently TD 20w is tracking west-northwestward along the southern 
boundary of a mid-to-low level subtropical ridge anchored over 
3. Forecast reasoning.
   A. TD 22w has slowed down to considerably in the last six hours 
resulting in a deteriorating upper-level environment, as a result 
further intensification is unlikely.  
   B. TD 20w will continue to track generally northwestward over the 
next 48 hours as the subtropical ridge builds extending westward 
over China. Moderate to high vertical wind shear will persist for 
the next 24 hours hindering further consolidation of the system to 
consolidate as it traverses over the warm waters of the South China 
Sea. TD 20w is expected to maintain intensity at 30 knots for the 
next 12 hours before making landfall over hainan, and reemerging 
over the Gulf of Tonkin by tau 24. Land interaction with hainan will 
begin to weaken the system before making landfall again over 
northern Vietnam. The system will continue to track inland 
dissipating by tau 48. Dynamic model guidance shows fairly good 
agreement, lending high confidence in the forecast track.//

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