413  
WTNT43 KNHC 161443  
TCDAT3  
 
POST-TROPICAL CYCLONE HELENE DISCUSSION NUMBER 37  
NWS NATIONAL HURRICANE CENTER MIAMI FL AL082018  
1100 AM AST SUN SEP 16 2018  
 
HELENE'S CLOUD PATTERN HAS TRANSFORMED INTO THAT OF AN  
EXTRATROPICAL CYCLONE, WITH A LARGE AREA OF COLD CLOUD TOPS  
LOCATED WELL TO THE NORTH AND NORTHWEST OF THE CENTER. AN ASCAT  
PASS THAT CAUGHT THE EASTERN PORTION OF THE CIRCULATION REVEALED  
MAXIMUM WINDS OF 40 TO 45 KT, THEREFORE THE INITIAL WIND SPEED  
REMAINS 45 KT FOR THIS ADVISORY. THE GLOBAL MODELS SUGGEST THAT  
THE SYSTEM WILL STRENGTHEN SLIGHTLY TODAY DUE TO BAROCLINIC  
PROCESSES, AND THIS IS REFLECTED IN THE OFFICIAL FORECAST.  
WEAKENING IS ANTICIPATED BY LATE MONDAY, AND THE SYSTEM IS FORECAST  
TO BE ABSORBED BY A LARGER LOW PRESSURE TO THE NORTHWEST OF THE  
UNITED KINGDOM BY TUESDAY MORNING.  
 
THE CYCLONE IS MOVING QUICKLY NORTHEASTWARD OR 055/25 KT. NOW THAT  
THE SYSTEM IS EMBEDDED WITHIN THE MID-LATITUDE WESTERLIES, A  
NORTHEASTWARD MOTION WITH SOME ADDITIONAL INCREASE IN FORWARD SPEED  
IS EXPECTED OVER THE NEXT DAY OR SO. THE GLOBAL MODELS REMAIN IN  
GOOD AGREEMENT ON THE TRACK OF THE POST-TROPICAL LOW, AND THE NEW  
OFFICIAL FORECAST IS AN UPDATE OF THE PREVIOUS ADVISORY.  
 
THIS IS THE LAST NHC ADVISORY ON THIS SYSTEM. INTERESTS IN IRELAND  
AND THE UNITED KINGDOM SHOULD CONSULT PRODUCTS FROM THEIR LOCAL  
METEOROLOGICAL SERVICE FOR INFORMATION ABOUT POTENTIAL IMPACTS FROM  
THE POST-TROPICAL CYCLONE. LOCAL FORECASTS AND WARNINGS FOR THE UK  
CAN BE FOUND ON THE WEBSITE OF THE UK MET OFFICE AT  
HTTPS://WWW.METOFFICE.GOV.UK/. LOCAL FORECASTS AND WARNINGS FOR  
IRELAND CAN BE FOUND ON THE WEBSITE OF MET EIREANN  
AT HTTPS://WWW.MET.IE/.  
 
FORECAST POSITIONS AND MAX WINDS  
 
INIT 16/1500Z 43.8N 25.7W 45 KT 50 MPH...POST-TROPICAL  
12H 17/0000Z 45.8N 21.2W 50 KT 60 MPH...POST-TROP/EXTRATROP  
24H 17/1200Z 49.0N 14.8W 50 KT 60 MPH...POST-TROP/EXTRATROP  
36H 18/0000Z 52.8N 6.2W 40 KT 45 MPH...POST-TROP/EXTRATROP  
48H 18/1200Z...ABSORBED  
 

 
FORECASTER BROWN  
 
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