HURRICANE GONZALO DISCUSSION NUMBER 13
NWS NATIONAL HURRICANE CENTER MIAMI FL AL082014
1100 AM AST WED OCT 15 2014
Data from an Air Force reconnaissance aircraft indicate that
Gonzalo has strengthened a little. The maximum 700 mb flight-level
wind reported was 123 kt and the highest SFMR wind observation was
116 kt. Based on these data, the initial wind speed is increased to
115 kt, making Gonzalo a category 4 hurricane on the Saffir-Simpson
Hurricane Wind Scale. This is the first category 4 hurricane in the
Atlantic basin since Ophelia in 2011. The aircraft data and
microwave images clearly show concentric eyewalls, with the
inner radius of maximum wind now only about 4-5 n mi from the
center.
Smoothing through the trochoidal oscillation of the eye yields an
initial motion estimate of 320/10 kt. A high amplitude trough over
the eastern United States is expected to slowly move eastward during
the next couple of days, and will erode the subtropical ridge that
is currently steering Gonzalo. This change in the large-scale
pattern should cause the hurricane to turn northward by early
Thursday and north-northeastward Thursday night and Friday, likely
bringing Gonzalo near Bermuda in about 2 days. Beyond 48 hours, the
hurricane is forecast to accelerate generally northeastward. The
track model guidance remains tightly clustered, and the official
forecast is near the GFS and ECMWF solutions and only slightly to
the left of the previous one.
Given the evidence of concentric eyewalls, and with the inner
eyewall already about as small as it can get, the current period of
intensification could be about over. The hurricane will likely
fluctuate in strength while the environmental conditions remain
favorable during the next day or two. After that time, weakening
is forecast when the hurricane moves into an atmosphere of
increasing southwesterly shear and drier air, and over much colder
water. Post-tropical transition will likely occur in 3 to 4 days
when the cyclone is forecast to cross the north wall of the Gulf
Stream current. Little change was made to the previous intensity
forecast, and this one lies near the middle of the guidance
envelope.
LOCATION...25.3N 68.7W
ABOUT 540 MI...865 KM SSW OF BERMUDA
MAXIMUM SUSTAINED WINDS...140 MPH...220 KM/H
PRESENT MOVEMENT...N OR 360 DEGREES AT 9 MPH...15 KM/H
MINIMUM CENTRAL PRESSURE...945 MB...27.91 INCHES
SUMMARY OF 1100 AM AST...1500 UTC...INFORMATION
-----------------------------------------------
LOCATION...26.1N 68.6W
ABOUT 485 MI...780 KM SSW OF BERMUDA
MAXIMUM SUSTAINED WINDS...145 MPH...230 KM/H
PRESENT MOVEMENT...N OR 5 DEGREES AT 7 MPH...11 KM/H
MINIMUM CENTRAL PRESSURE...940 MB...27.76 INCHES
