000
WTNT43 KNHC 131452
TCDAT3

TROPICAL STORM GONZALO DISCUSSION NUMBER   5
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL082014
1100 AM AST MON OCT 13 2014

An Air Force Reserve reconnaissance aircraft investigating Gonzalo
this morning found 850 mb maximum flight-level winds of 64 kt along
with reliable SFMR surface winds near 55 kt in the northeastern
quadrant, plus a central pressure of 992 mb. In addition, the
Antigua-Barbuda Meteorological Service recently reported a sustained
wind of 58 kt and a gust to 76 kt. Based on these data, the
intensity has been increased to 55 kt. Reports from the aircraft
radar and Antigua-Barbuda also indicate the center of Gonzalo passed
over Antigua between 1300-1400 UTC.

The initial motion estimate is 290/9 kt. Gonzalo is expected to
continue to move west-northwestward today, and turn toward the
northwest after 24 hours when the cyclone clears the northern Lesser
Antilles. After that, the mid-level ridge to the north of Gonzalo is
expected to break down as a strong mid-latitude trough moving off of
the U.S. east and southeast coasts approaches the area north of
Puerto Rico and Hispaniola in about 72 hours. The weakening ridge
will allow Gonzalo to move slowly northward, and then turn toward
the northeast and accelerate on Days 4 and 5. The latest NHC model
guidance appears to have stabilized and has no longer made any
eastward shifts, so the official forecast track is just an update of
the previous advisory track, which lies close to a blend of the GFEX
and TVCN consensus models.

The satellite presentation of Gonzalo has continued to improve, and
radar data from Guadeloupe indicates that a small but intense vortex
may have passed over Antigua earlier this morning. Overall, the
improvement in the horizontal and vertical structure of Gonzalo the
past several hours, along with weak vertical wind shear and SSTs
greater than 29C, should allow for at least steady strengthening of
the cyclone through the next 96 hours. By 120 hours, southwesterly
wind shear of around 20 kt is expected to affect Gonzalo, which
should induce a slow weakening trend. The NHC intensity forecast is
similar to the previous forecast and the SHIPS intensity model.

Gonzalo is forecast to be reaching hurricane strength by the time it
passes near the British Virgin Islands, and so a hurricane warning
is in effect there.  Although hurricane conditions are not currently
expected in the U.S. Virgin Islands, only a slight deviation to the
left of the forecast track, or a more rapid strengthening of the
storm, would result in the need to extend the hurricane warning into
those areas. Interests in the hurricane watch area are reminded that
the watch means that hurricane conditions are possible...and in this
case within 24 hours.

FORECAST POSITIONS AND MAX WINDS

INIT  13/1500Z 17.2N  61.9W   55 KT  65 MPH
 12H  14/0000Z 18.0N  63.3W   60 KT  70 MPH
 24H  14/1200Z 19.4N  65.0W   70 KT  80 MPH
 36H  15/0000Z 20.8N  66.4W   75 KT  85 MPH
 48H  15/1200Z 22.4N  67.5W   80 KT  90 MPH
 72H  16/1200Z 24.8N  68.0W   90 KT 105 MPH
 96H  17/1200Z 27.4N  66.9W   95 KT 110 MPH
120H  18/1200Z 31.7N  64.0W   90 KT 105 MPH

$$
Forecaster Stewart

000
WTNT43 KNHC 140242
TCDAT3

HURRICANE GONZALO DISCUSSION NUMBER   7
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL082014
1100 PM AST MON OCT 13 2014

The eye of Gonzalo moved just north of St. Maarten and over Anguilla
earlier this evening. St. Maarten reported a peak 2-minute wind of
55 kt and a gust of 65 kt with a minimum pressure of 994 mb. Data
from the Hurricane Hunter aircraft earlier indicated peak 700-mb
flight-level winds of around 85 kt, which support an intensity of 75
kt for this advisory. This intensity is also supported by the latest
Dvorak classification of T4.5 from TAFB. The next Hurricane Hunter
aircraft will be investigating Gonzalo around 0600 UTC.

Gonzalo appears to be poised to intensify, perhaps rapidly, in the
next day or so. The inner-core features are quite distinct in
recent microwave imagery and a warm spot has recently developed in
infrared imagery with a more symmetric cloud pattern. Given these
trends and the overall favorable environment, the intensity
forecast has been adjusted upward and is close to the the SHIPS
model on the high end of the intensity guidance through the first 48
hours, showing Gonzalo becoming a major hurricane in about 36 hours.
As Gonzalo gains latitude later in the period, southwesterly shear
ahead of a mid-latitude trough and cooler SSTs should result in
gradual weakening.

The eye of Gonzalo is now evident in WSR-88D imagery from San Juan,
and the initial motion estimate is 315/10. Overall, the track
forecast reasoning remains unchanged, as the hurricane will
move northwestward into a weakness in the subtropical ridge and
then accelerate northward and northeastward ahead of a mid-latitude
trough moving off the east coast of the United States. The new NHC
track forecast has been shifted a little to the right in the first
48 hours due to the initial position and motion and an adjustment
and toward the latest multi-model consensus. Beyond that time, the
new NHC forecast is largely and update of the previous one and is
close to but a bit slower than a blend of the GFS and ECMWF models,
especially by day 5.

FORECAST POSITIONS AND MAX WINDS

INIT  14/0300Z 18.7N  63.4W   75 KT  85 MPH
 12H  14/1200Z 19.8N  64.7W   85 KT 100 MPH
 24H  15/0000Z 21.5N  66.1W   95 KT 110 MPH
 36H  15/1200Z 23.1N  67.4W  100 KT 115 MPH
 48H  16/0000Z 24.5N  68.1W  105 KT 120 MPH
 72H  17/0000Z 27.3N  67.9W  100 KT 115 MPH
 96H  18/0000Z 31.5N  65.5W   95 KT 110 MPH
120H  19/0000Z 37.0N  61.0W   85 KT 100 MPH

$$
Forecaster Brennan

000
WTNT43 KNHC 150256
TCDAT3

HURRICANE GONZALO DISCUSSION NUMBER  11
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL082014
1100 PM AST TUE OCT 14 2014

Data from an Air Force Hurricane Hunter reconnaissance aircraft
indicate that Gonzalo has continued to strengthen.  The plane
reported maximum flight-level of 125 kt in the northeastern
quadrant and peak SFMR winds of 108 kt. The minimum surface pressure
also has fallen about 17 mb during the last 9 hours to 954 mb.
Satellite images show that the eye has warmed and shrunk to a
diameter of 10 n mi while the inner core has generally become better
defined. However, Gonzalo has been maintaining an asymmetric
distribution of convection, presumably due to around 15 kt of
south-southwesterly shear of affecting the cyclone according to the
latest SHIPS and UW-CIMSS shear analyses. A blend of the flight-
level and SFMR wind data is used to raise the initial intensity of
110 kt.

Water vapor imagery and cloud-tracked wind vectors show an upper-
level trough between Bermuda and the southeastern U.S. responsible
for the south-southwesterly shear over Gonzalo, but the shear should
not be enough to prevent additional intensification from taking
place over warm waters of 28-29 deg C during the next day or so.
At some point during this time, fluctuations in strength due to
difficult-to-forecast inner core evolution are probable. By 72
hours, a significant increase in south-southwesterly shear should
induce a considerable weakening trend. Increasing baroclinicity in
the near-storm environment, much cooler waters, and drier and more
stable air wrapping around the hurricane's circulation should result
in extratropical transition by day 4. The NHC intensity forecast is
about the same as the previous one, and is near or higher than the
highest intensity guidance (SHIPS/LGEM) through 36 hours but close
to the multi-model consensus after that.

Gonzalo has continued to move on a northwestward course, or 320/11,
though the center has wobbled a bit toward the left during the
last couple of hours.  The hurricane should gradually turn north-
northwestward and then northward and slow down as it moves around
the western periphery of an eastward-shifting central Atlantic ridge
during the next 24 to 36 hours.  By 48 hours, Gonzalo should
encounter a deep-layer south-southwesterly flow associated with a
potent mid-latitude trough swinging out of the east-central United
States. This flow pattern should turn Gonzalo north-northeastward
with increasing forward speed.  Although the track guidance is
tightly clustered through 72 hours, there is still some along-track
spread in the model solutions, with the ECMWF depicting a weaker and
much-slower-moving cyclone.  The new NHC forecast places less weight
on the ECMWF, owing to Gonzalo's current intensity. The official NHC
forecast lies on the far eastern side of the guidance envelope and
to the right of the multi-model consensus.


FORECAST POSITIONS AND MAX WINDS

INIT  15/0300Z 22.2N  66.6W  110 KT 125 MPH
 12H  15/1200Z 23.4N  67.6W  120 KT 140 MPH
 24H  16/0000Z 24.9N  68.5W  120 KT 140 MPH
 36H  16/1200Z 26.3N  68.7W  115 KT 130 MPH
 48H  17/0000Z 28.5N  67.7W  110 KT 125 MPH
 72H  18/0000Z 34.7N  64.1W  100 KT 115 MPH
 96H  19/0000Z 45.1N  56.7W   80 KT  90 MPH...POST-TROP/EXTRATROP
120H  20/0000Z 52.5N  42.0W   65 KT  75 MPH...POST-TROP/EXTRATROP

$$
Forecaster Kimberlain