Tropical Storm MIRIAM

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TROPICAL STORM MIRIAM DISCUSSION NUMBER   5
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP142006
200 AM PDT SUN SEP 17 2006
 
MIRIAM IS A SHEARED TROPICAL STORM WITH ALL OF THE DEEP CONVECTION
DISPLACED TO THE SOUTHWEST OF THE LOW-LEVEL CENTER.  BASED ON A
QUIKSCAT OVERPASS AT 0220 UTC...A COUPLE OF NEARBY SHIP
OBSERVATIONS...AND ON AN OBJECTIVE DVORAK ESTIMATE USING THE SHEAR
PATTERN...THE ADVISORY INTENSITY IS KEPT AT 40 KT.  THE WIND SHEAR
IS FORECAST BY THE GLOBAL MODELS TO INCREASE DURING THE NEXT COUPLE
OF DAYS...SO STRENGTHENING DOES NOT APPEAR VERY LIKELY.  ON THE
CONTRARY...THE SHIPS AND GFDL BOTH FORECAST GRADUAL WEAKENING...AND
SO DOES THE OFFICIAL FORECAST AT A SLIGHTLY FASTER RATE THAN THE
PREVIOUS ADVISORY.  WEAKENING WILL ALSO BE HASTENED WHEN THE
CYCLONE REACHES COOLER WATERS IN A FEW DAYS.

USING SEVERAL PASSIVE MICROWAVE OVERPASSES AND A COUPLE OF QUIKSCAT
OVERPASSES DURING THE PAST 18 HOURS OR SO...THE FORWARD MOTION
APPEARS TO HAVE BEEN ABOUT 015/4.  WITH LANE WEAKENING OVER
LAND...ITS INFLUENCE ON MIRIAM IS NOT ALL THAT SIGNIFICANT AND THE
STEERING CURRENTS SHOULD REMAIN WEAK.  THE NEW OFFICIAL FORECAST
CONTINUES TO SHOW A GRADUAL TURN TO THE NORTH AND THEN
NORTH-NORTHWEST...AT A CONTINUED SLOW PACE...IN ACCORDANCE WITH
MOST OF THE GUIDANCE...BUT IS ADJUSTED A BIT TO THE LEFT CLOSER TO
THE CONSENSUS.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      17/0900Z 19.1N 113.9W    40 KT
 12HR VT     17/1800Z 19.7N 113.7W    40 KT
 24HR VT     18/0600Z 20.5N 113.5W    40 KT
 36HR VT     18/1800Z 21.5N 113.7W    35 KT
 48HR VT     19/0600Z 22.4N 114.3W    30 KT
 72HR VT     20/0600Z 24.0N 115.5W    25 KT...DISSIPATING
 96HR VT     21/0600Z 25.0N 116.0W    20 KT...REMNANT LOW
120HR VT     22/0600Z...DISSIPATED
 
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FORECASTER KNABB
 
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