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Tropical Storm COSME (Text)

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TROPICAL STORM COSME DISCUSSION NUMBER   4
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP032013
200 AM PDT MON JUN 24 2013
 
DURING THE PAST 6 HOURS...CONVECTION HAS INCREASED SOMEWHAT NEAR THE
CENTER OF THE TROPICAL CYCLONE...AND SEVERAL SATELLITE INTENSITY
ESTIMATES INDICATE THAT THE SYSTEM HAS STRENGTHENED INTO TROPICAL
STORM COSME. IN FACT...ASCAT-B AND ASCAT-A SCATTEROMETER PASSES AT
0404Z AND 0450Z...RESPECTIVELY...INDICATED SEVERAL 34- TO 37-KT
WIND VECTORS IN THE SOUTHEASTERN QUADRANT. THE ASCAT DATA ALSO
REVEALED THAT COSME HAD MOVED MORE WESTWARD SINCE THE PREVIOUS
ADVISORY...AND THAT THE CENTER AS LOCATED ON THE NORTHERN EDGE OF A
SMALL CDO-LIKE CONVECTIVE FEATURE.

THE INITIAL MOTION ESTIMATE IS 305/09 KT. NORTHERLY TO NORTHEASTERLY
MID-LEVEL SHEAR OF 10-15 KT AS INDICATED IN UW-CIMMS SHEAR ANALYSES
IS THE LIKELY REASON FOR THE RECENT WESTWARD MOTION. HOWEVER...
THIS IS EXPECTED TO BE A TEMPORARY MOTION AND COSME IS FORECAST TO
BEGIN TO TURN BACK TOWARD THE NORTHWEST LATER THIS MORNING AS THE
CYCLONE GRADUALLY MOVES OUT OF THE NORTHERLY MID-LEVEL SHEAR
ENVIRONMENT. AFTERWARDS...A DEEP-LAYER RIDGE TO THE NORTH OF COSME
SHOULD GRADUALLY TURN THE CYCLONE TOWARD THE WEST-NORTHWEST BY 48
HOURS. NEAR THE END OF THE FORECAST PERIOD...THE EXPECTED WEAKENING
AND VERTICALLY SHALLOW CYCLONE SHOULD BE STEERED WESTWARD WITHIN
THE LOW-LEVEL EASTERLY TRADE WIND FLOW. SINCE COSME IS ALREADY AT
LEAST 30 NMI TO THE LEFT OF THE PREVIOUS FORECAST TRACK...THE NEW
ADVISORY TRACK HAS BEEN SHIFTED SLIGHTLY TO THE WEST AND SOUTH...
AND BASICALLY LIES ALONG THE EXTREME SOUTHERN EDGE OF TIGHTLY
PACKED MODEL GUIDANCE ENVELOPE.
 
THE AFOREMENTIONED MID-LEVEL SHEAR THAT HAS BEEN UNDERCUTTING THE
OTHERWISE VERY FAVORABLE UPPER-LEVEL OUTFLOW PATTERN HAS BEEN
HINDERING THE  DEVELOPMENT OF PERSISTENT DEEP CONVECTION NEAR THE
CENTER. HOWEVER...AS COSME CONTINUES TO MOVE NORTHWESTWARD...THE
CYCLONE WILL ENTER A LESS HOSTILE SHEAR ENVIRONMENT...WHICH WILL
ALLOW FOR MORE SIGNIFICANT STRENGTHENING TO OCCUR UNTIL THE SYSTEM
REACHES MUCH COOLER WATERS BY 72 HOURS.  DESPITE VERY FAVORABLE
ATMOSPHERIC AND OCEANIC CONDITIONS FOR THE NEXT 2-3 DAYS...THE
LARGE RADIUS OF MAXIMUM WINDS OF AT LEAST 90 NMI SHOULD KEEP
INTENSIFICATION SLOWER THAN THE AVERAGE RATE OF ONE T-NUMBER PER
DAY. BY 72 HOURS...COSME WILL BE MOVING OVER COOLER WATERS AND
RAPID WEAKENING IS EXPECTED TO ENSUE. THE OFFICIAL INTENSITY
FORECAST IS SIMILAR TO THE PREVIOUS ADVISORY...AND IS SIMILAR TO A
BLEND OF THE SHIPS AND SHIFOR INTENSITY MODELS.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  24/0900Z 12.8N 105.2W   35 KT  40 MPH
 12H  24/1800Z 13.9N 106.5W   40 KT  45 MPH
 24H  25/0600Z 15.2N 108.5W   45 KT  50 MPH
 36H  25/1800Z 16.2N 110.8W   55 KT  65 MPH
 48H  26/0600Z 17.0N 113.3W   65 KT  75 MPH
 72H  27/0600Z 18.5N 118.3W   50 KT  60 MPH
 96H  28/0600Z 19.7N 124.0W   35 KT  40 MPH
120H  29/0600Z 20.0N 129.2W   25 KT  30 MPH...POST-TROP/REMNT LOW
 
$$
FORECASTER STEWART
 
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