Tropical Storm MIRIAM

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TROPICAL STORM MIRIAM DISCUSSION NUMBER   7
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP142006
200 PM PDT SUN SEP 17 2006
 
MIRIAM HAS BECOME LESS ORGANIZED THIS AFTERNOON WITH DIMINISHING
CONVECTION SOUTHWEST OF AN EXPOSED LOW-LEVEL CENTER OF CIRCULATION.
OBVIOUSLY THIS SYSTEM IS FEELING THE EFFECTS OF VERTICAL WIND SHEAR
AND PERHAPS DRY AIR ENTRAINMENT. OBSERVATIONS FROM THE MEXICAN NAVY
AT ISLA CLARION REPORTED MAXIMUM WINDS NEAR 26 KT AND GUSTS TO 39
KT OVER THE PAST FEW HOURS. SHIP A8HR7 ABOUT 170 NM TO THE
SOUTHWEST OF THE CENTER REPORTED 39 KT...HOWEVER THESE WINDS WERE
ON THE PERIPHERY OF THE CIRCULATION AND LIKELY NOT REPRESENTATIVE
OF MIRIAM'S ACTUAL INTENSITY. MOREOVER A QUALITY CONTROL CHECK FROM
THE OCEAN PREDICTION CENTER INDICATED THAT THE SHIP'S WINDS WERE
RUNNING A LITTLE HIGH. BASED ON THESE OBSERVATIONS AND CURRENT
INTENSITY NUMBERS OF 2.5 FROM TAFB AND SAB...THE INITIAL INTENSITY
IS REDUCED TO 35 KT. MIRIAM WILL BE MOVING INTO AN AREA OF
INCREASED WIND SHEAR AND COOLER WATERS OVER THE NEXT COUPLE OF DAYS
AS INDICATED BY MOST OF THE GLOBAL MODELS. THEREFORE...THE OFFICIAL
FORECAST CALLS FOR STEADY WEAKENING TO A REMNANT LOW IN 72 HOURS...
BUT THIS COULD OCCUR SOONER.
 
THE FORWARD MOTION IS A SLOW 010/4...SINCE MIRIAM IS EMBEDDED WITHIN
RATHER WEAK STEERING CURRENTS. MODELS ARE IN FAIR AGREEMENT IN
INDICATING A NORTHWARD MOTION FOLLOWED BY A MORE NORTHWESTWARD TURN
AS THE SYSTEM BECOMES SHALLOW AND STEERED BY THE LOW-LEVEL FLOW.
THIS FORECAST IS SIMILAR TO BUT NUDGED TO THE LEFT OF THE PREVIOUS
ONE TO BE BETTER ALIGNED WITH THE MODEL CONSENSUS.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      17/2100Z 19.3N 114.0W    35 KT
 12HR VT     18/0600Z 20.1N 114.0W    30 KT
 24HR VT     18/1800Z 20.9N 114.6W    30 KT
 36HR VT     19/0600Z 21.9N 115.6W    25 KT
 48HR VT     19/1800Z 23.0N 116.5W    25 KT...DISSIPATING
 72HR VT     20/1800Z 25.0N 117.5W    20 KT...REMNANT LOW
 96HR VT     21/1800Z...DISSIPATED
 
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FORECASTER MAINELLI/CANGIALOSI
 
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