Tropical Storm GONZALO

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TROPICAL STORM GONZALO DISCUSSION NUMBER   2
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL082014
500 PM AST SUN OCT 12 2014

The Air Force Reserve reconnaissance aircraft investigating Gonzalo
this afternoon has found found 850-mb maximum flight-level winds of
47 kt in the northeastern quadrant along with reliable SFMR surface
winds of 39-41 kt. The aircraft also measured a central pressure of
1003-1004 mb and on-board radar indicated that a primitive eye with
a diameter of 10 n mi was developing. Based on these data, the
initial intensity has been increased to 40 kt, which could be a
little conservative.

The initial motion estimate is 270/10 kt based on reconnaissance
data. There is no significant change to the previous track forecast
or reasoning. A strong deep-layer ridge to the north of Gonzalo
should keep the cyclone moving westward at around 10 kt for the next
24 hours, followed by a gradual turn to the west-northwest by 36
hours. By 72 hours, a strong mid-latitude trough is expected to move
off of the U.S. east coast and act to erode the ridge to the north
of Hispaniola, allowing Gonzalo to move slowly northwestward to
northward into the weakness in the ridge. The NHC model guidance is
in general agreement on this developing track scenario, but there is
considerable spread in the model tracks after 36 hours. The GFS and
the regional models keep Gonzalo weak until after 48 hours, and take
the system well to the east of Puerto Rico and the Virgin Islands.
In contrast, the ECMWF and the UKMET show a vertically deep and more
robust tropical cyclone moving more westward in deep-layer easterly
steering flow. Since the official forecast calls for Gonzalo to
become a hurricane within 48 hours, the NHC forecast track lies near
the extreme western edge of the model envelope and close to the more
robust ECMWF model solution.

The combination of the small size of Gonzalo, its precursor eye
feature, low vertical wind shear conditions, SSTs at least 29C, and
colder than normal upper-tropospheric temperatures support at least
a normal rate of intensification throughout the forecast period.
Although occasional intrusions of dry mid-level air could briefly
disrupt the strengthening process, those occurrences should
generally be short-lived due to the strong instability conditions
that will be present. In fact, rapid intensification is a very
distinct possibility, especially if the aforementioned eye feature
continues to develop. The NHC intensity forecast is higher then the
consensus models and follows the a blend of the SHIPS and LGEM
models.

NOTE: Data from the reconnaissance aircraft has been received by the
NHC, but telecommunications problems continue to prevent the
dissemination of these data.

FORECAST POSITIONS AND MAX WINDS

INIT  12/2100Z 16.4N  59.5W   40 KT  45 MPH
 12H  13/0600Z 16.5N  61.1W   45 KT  50 MPH
 24H  13/1800Z 16.9N  63.1W   50 KT  60 MPH
 36H  14/0600Z 17.9N  65.0W   60 KT  70 MPH
 48H  14/1800Z 19.0N  66.4W   70 KT  80 MPH
 72H  15/1800Z 20.9N  67.9W   80 KT  90 MPH
 96H  16/1800Z 22.6N  68.3W   90 KT 105 MPH
120H  17/1800Z 24.5N  68.0W   95 KT 110 MPH

$$
Forecaster Stewart

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