302  
WTNT42 KNHC 102039  
TCDAT2  
 
TROPICAL STORM OPHELIA DISCUSSION NUMBER 7  
NWS NATIONAL HURRICANE CENTER MIAMI FL AL172017  
500 PM AST TUE OCT 10 2017  
 
THE OVERALL CONVECTIVE STRUCTURE OF OPHELIA HAS IMPROVED MARKEDLY  
OVER THE PAST SEVERAL, INCLUDING THE DEVELOPMENT OF NUMEROUS,  
TIGHTLY CURVED BANDS AND A BURST OF DEEP CONVECTION NEAR THE CENTER.  
UPPER-LEVEL ANTICYCLONIC OUTFLOW HAS ALSO INCREASED AND EXPANDED IN  
ALL QUADRANTS. DVORAK SATELLITE CURRENT INTENSITY ESTIMATES ARE  
T3.5/55 KT FROM TAFB AND T4.0/65 KT FROM SAB, SO THE INITIAL  
INTENSITY HAS BEEN CONSERVATIVELY INCREASED TO 50 KT. A 28-30 KT  
WIND REPORT FROM SHIP PBQL, LOCATED MORE 200 NMI NORTHWEST OF THE  
CENTER, INDICATES THAT THE OUTER CIRCULATION IS ALSO STRENGTHENING.  
 
THE INITIAL MOTION ESTIMATE IS 135/04 KT. OPHELIA IS FORECAST TO  
CONTINUE MOVING SOUTHEASTWARD AT A SLOW BUT STEADY PACE FOR THE NEXT  
48 HOURS OR SO WHILE THE CYCLONE REMAINS EMBEDDED WITHIN A BROAD  
MID-/UPPER-LEVEL TROUGH. THE NHC MODEL GUIDANCE REMAINS IN GOOD  
AGREEMENT ON THE OPHELIA BEGINNING TO LIFT OUT TO THE NORTHEAST BY  
72 H, AND THEN GRADUALLY ACCELERATE INTO THE MID-LATITUDE WESTERLIES  
AHEAD OF AN EASTWARD-MOVING MID-TROPOSPHERIC TROUGH. THE LATEST  
MODEL GUIDANCE REMAINS TIGHTLY PACKED, BUT IT HAS ALSO SHIFTED  
NORTHWARD, WHICH BRINGS OPHELIA CLOSER TO THE AZORES IN THE 96-120  
HOUR PERIOD. HOWEVER, THE NEW FORECAST TRACK WAS NOT SHIFTED  
NORTHWARD AND REMAINS ALONG THE SOUTHERN EDGE OF THE GUIDANCE  
ENVELOPE BETWEEN THE NOAA HCCA CONSENSUS MODEL AND THE MORE  
SOUTHERLY ECMWF MODEL.  
 
THE GFS AND ECMWF MODELS CONTINUE TO FORECAST ONLY MODEST  
INTENSIFICATION FOR THE NEXT 48-72 HOURS, DESPITE THE VERTICAL WIND  
SHEAR BEING FAIRLY LOW AT LESS THAN 10 KT. HOWEVER, THOSE MODELS ARE  
FORECASTING MORE VIGOROUS STRENGTHENING AFTER 96 H AS OPHELIA  
EXPERIENCES SOME BAROCLINIC INTERACTION, ESPECIALLY BY 120 HOURS.  
THE STRONG BAROCLINIC DEEPENING ON DAY 5 COULD BE OVERDONE SOMEWHAT  
GIVEN THAT THE BEST JETSTREAM DYNAMICS ARE FORECAST TO BE ABOUT 300  
NMI NORTHWEST OF THE SURFACE LOW AND FRONTAL ZONE. FOR NOW, THE  
OFFICIAL INTENSITY FORECAST REMAINS SIMILAR TO THE PREVIOUS  
ADVISORY, AND IS LITTLE LOWER THAN THE INTENSITY CONSENSUS MODELS  
HCCA AND IVCN AND THE GFS AND ECMWF SOLUTIONS ON DAYS 4 AND 5.  
 
FORECAST POSITIONS AND MAX WINDS  
 
INIT 10/2100Z 31.1N 38.0W 50 KT 60 MPH  
12H 11/0600Z 30.6N 37.5W 55 KT 65 MPH  
24H 11/1800Z 30.2N 36.8W 60 KT 70 MPH  
36H 12/0600Z 30.2N 36.4W 65 KT 75 MPH  
48H 12/1800Z 30.5N 35.6W 70 KT 80 MPH  
72H 13/1800Z 32.0N 32.2W 70 KT 80 MPH  
96H 14/1800Z 34.7N 25.8W 70 KT 80 MPH  
120H 15/1800Z 39.0N 17.0W 70 KT 80 MPH...POST-TROP/EXTRATROP  
 

 
FORECASTER STEWART  
 
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