922  
WTPZ45 KNHC 271438  
TCDEP5  
 
TROPICAL STORM SELMA DISCUSSION NUMBER 2  
NWS NATIONAL HURRICANE CENTER MIAMI FL EP202017  
1000 AM CDT FRI OCT 27 2017  
 
SELMA IS A SHEARED TROPICAL CYCLONE. EARLY MORNING VISIBLE  
SATELLITE IMAGES AND RECENT MICROWAVE IMAGERY SHOW THAT THE CENTER  
IS LOCATED NEAR THE NORTHEASTERN EDGE OF A SMALL, BUT PERSISTENT  
CLUSTER OF DEEP CONVECTION. THE LATEST SUBJECTIVE DVORAK INTENSITY  
ESTIMATES ARE STILL BELOW TROPICAL STORM STRENGTH, BUT THE INITIAL  
INTENSITY REMAINS AT 35 KT, IN AGREEMENT WITH THE EARLIER  
SCATTEROMETER DATA.  
 
RECENT SATELLITE AND MICROWAVE FIXES INDICATE THAT SELMA IS MOVING  
NORTHWESTWARD AT ABOUT 4 KT. A WEAK RIDGE TO THE NORTH OF THE  
TROPICAL CYCLONE IS FORECAST TO WEAKEN TODAY AS A LARGE MID-LATITUDE  
TROUGH MOVES INTO THE GULF OF MEXICO. THIS PATTERN SHOULD CAUSE  
SELMA TO TURN NORTHWARD TOWARD THE PACIFIC COAST OF CENTRAL AMERICA  
TONIGHT AND EARLY SATURDAY. HOWEVER, THERE IS A LARGE SPREAD IN THE  
GUIDANCE REGARDING THE SHARPNESS OF THE TURN. THE UKMET SHOWS AN  
IMMEDIATE NORTHWARD OR NORTHEASTWARD MOTION AND IS ALONG THE RIGHT  
SIDE OF THE GUIDANCE ENVELOPE. ON THE OPPOSITE SIDE OF THE ENVELOPE  
ARE THE GFS, HWRF, AND HMON, WHICH DEPICT A LONGER NORTH-  
NORTHWESTWARD MOTION AND BRING SELMA INLAND NEAR WESTERN GUATEMALA.  
THE NHC FORECAST IS CLOSEST TO THE ECMWF AND HFIP CORRECTED  
CONSENSUS MODELS, WHICH ARE A LITTLE TO THE RIGHT OF THE MULTI-MODEL  
CONSENSUS. GIVEN THE LARGE UNCERTAINTY IN THE TRACK FORECAST, THE  
GOVERNMENT OF GUATEMALA HAS ISSUED A TROPICAL STORM WATCH FOR THE  
ENTIRE PACIFIC COAST OF GUATEMALA.  
 
THE SHEAR OVER SELMA APPEARS TO BE A LITTLE STRONGER THAN INITIALLY  
EXPECTED, AND THE SHIPS GUIDANCE DOES NOT SHOW ANY DECREASE IN THIS  
SHEAR DURING THE NEXT DAY OR SO. AS A RESULT, ONLY SLIGHT  
STRENGTHENING IS INDICTED BEFORE LANDFALL, AND THE NHC FORECAST IS  
CLOSE TO THE VARIOUS CONSENSUS MODELS. SINCE THE SYSTEM IS SMALL,  
IT IS EXPECTED TO WEAKEN AND DISSIPATE VERY QUICKLY AFTER IT MOVES  
INLAND OVER THE HIGH TERRAIN OF CENTRAL AMERICA.  
 
IT SHOULD BE NOTED THAT THE PRIMARY THREAT ASSOCIATED WITH SELMA  
IS HEAVY RAINFALL, WITH TOTALS POSSIBLY AS HIGH AS 10 INCHES  
OVER PORTIONS OF EL SALVADOR AND GUATEMALA. THIS RAINFALL COULD  
CAUSE LIFE-THREATENING FLASH FLOODS AND MUDSLIDES.  
 
FORECAST POSITIONS AND MAX WINDS  
 
INIT 27/1500Z 11.1N 89.5W 35 KT 40 MPH  
12H 28/0000Z 11.8N 89.9W 40 KT 45 MPH  
24H 28/1200Z 13.0N 90.0W 40 KT 45 MPH  
36H 29/0000Z 14.2N 89.8W 35 KT 40 MPH...INLAND  
48H 29/1200Z...DISSIPATED  
 

 
FORECASTER BROWN  
 
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