290  
WTNT43 KNHC 272045  
TCDAT3  
 
POTENTIAL TROPICAL CYCLONE EIGHTEEN DISCUSSION NUMBER 1  
NWS NATIONAL HURRICANE CENTER MIAMI FL AL182017  
500 PM EDT FRI OCT 27 2017  
 
DATA FROM AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT  
INVESTIGATING THE DISTURBANCE OVER THE NORTHWESTERN CARIBBEAN SEA  
INDICATE THAT THE SYSTEM DOES NOT YET HAVE A WELL-DEFINED CENTER. IN  
FACT, THE AIRCRAFT DATA AND SATELLITE IMAGERY SUGGEST THAT THERE ARE  
MULTIPLE CIRCULATIONS EMBEDDED WITHIN A BROADER CIRCULATION AT THIS  
TIME. GIVEN THE LACK OF A WELL-DEFINED CENTER, THE SYSTEM IS NOT A  
TROPICAL CYCLONE, BUT SINCE TROPICAL STORM CONDITIONS ARE EXPECTED  
TO AFFECT CUBA AND THE NORTHWESTERN BAHAMAS IN THE NEXT 24 TO 36  
HOURS, ADVISORIES ARE BEING INITIATED ON THE SYSTEM AS A POTENTIAL  
TROPICAL CYCLONE AT THIS TIME.  
 
THE INITIAL INTENSITY IS SET TO 35 KT BASED ON AIRCRAFT DATA, WITH  
THESE WINDS FOUND WELL SOUTH OF THE BROAD CIRCULATION CENTER.  
HOWEVER, NOAA BUOY 42057 ALSO REPORTED A PEAK 1-MINUTE WIND OF 31 KT  
EARLIER TODAY. AIRCRAFT DATA SUGGEST THAT THE CENTRAL PRESSURE IS  
AROUND 1006 MB. THE SYSTEM IS SITUATED IN A LOW-SHEAR ENVIRONMENT  
AND OVER WARM WATERS, SO SOME SLOW STRENGTHENING IS EXPECTED IN THE  
FIRST 24 HOURS BEFORE THE SYSTEM REACHES CUBA. THE OFFICIAL FORECAST  
FOLLOWS THE TREND OF THE INTENSITY CONSENSUS IN SHOWING A PEAK OF  
AROUND 45 KT AT 36 AND 48 HOURS BEFORE THE SYSTEM IS ABSORBED BY AN  
APPROACHING COLD FRONT IN 60-72 HOURS.  
 
GIVEN THE LACK OF A WELL-DEFINED CENTER, THE INITIAL POSITION IS AND  
THE INITIAL MOTION OF 330/05 ARE HIGHLY UNCERTAIN. A FASTER  
NORTHWARD MOTION SHOULD BEGIN SOON AS THE DISTURBANCE BEGINS TO  
RECURVE AHEAD OF AN APPROACHING MID/UPPER-LEVEL TROUGH MOVING INTO  
THE SOUTHEASTERN UNITED STATES. THIS TROUGH SHOULD CAUSE A FASTER  
NORTHEASTWARD ACCELERATION AT 24 THROUGH 48 HOURS. THE TRACK MODEL  
GUIDANCE IS IN GENERALLY GOOD AGREEMENT ON THE OVERALL SCENARIO,  
WITH MORE ALONG THAN CROSS TRACK SPREAD. THE NHC FORECAST LEANS  
TOWARD A BLEND OF THE ECMWF AND GFS MODELS AND IS A LITTLE SLOWER  
THAN THE CURRENT MULTI-MODEL CONSENSUS. NOT SURPRISINGLY, GIVEN THE  
DISORGANIZED INITIAL STATE OF THE SYSTEM, THE TRACK FORECAST  
UNCERTAINTY IS LARGER THAN USUAL.  
 
FORECAST POSITIONS AND MAX WINDS  
 
INIT 27/2100Z 17.5N 84.5W 35 KT 40 MPH...POTENTIAL TROP CYCLONE  
12H 28/0600Z 19.1N 84.1W 35 KT 40 MPH...TROPICAL STORM  
24H 28/1800Z 21.7N 82.4W 40 KT 45 MPH  
36H 29/0600Z 24.6N 79.6W 45 KT 50 MPH  
48H 29/1800Z 28.0N 75.5W 45 KT 50 MPH  
72H 30/1800Z...ABSORBED  
 

 
FORECASTER BRENNAN  
 
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