Remnants Of Sergio Discussion Number 54
NWS National Hurricane Center Miami FL EP212018
300 PM MDT Fri Oct 12 2018
The center of Sergio moved over the high terrain of northwestern
Mexico and no longer has a well-defined circulation center. On
this basis, NHC has issued the last advisory on this system. The
remnants of Sergio will move toward the northeast about 22 kt and
could still produce gusty winds in heavy squalls.
Sergio's remnants will continue to produce heavy rains which
could result in life-threatening flash flooding and mudslides
within mountainous terrain in northwestern Mexico. Flash
flooding is also possible across the U.S. Desert
Southwest and the Southern Plains through the weekend.
Hurricane Sergio Discussion Number 17
NWS National Hurricane Center Miami FL EP212018
800 AM PDT Wed Oct 03 2018
Sergio has intensified this morning, with the eye becoming better
defined while embedded in very cold cloud tops. The upper-level
outflow is restricted to the northeast of the hurricane, but strong
over the southern part of the circulation. Using a blend of
objective and subjective Dvorak estimates, the advisory intensity
estimate is 110 kt. Sergio will remain over warm waters of nearly
29 deg C, with moderate shear and a humid mid-level air mass for
the next day or so. Thus, some additional strengthening is forecast
in the short term. In a couple of days, slightly cooler waters and
some entrainment of dry air is likely to cause a gradual weakening
trend to begin. The NHC forecast is at the high end of the
intensity model guidance, and shows Sergio remaining a hurricane
throughout the entire forecast period.
The hurricane has turned toward the northwest, and is now moving at
about 305/9 kt. This turn is probably being caused by a weakness in
the mid-level ridge associated with a trough nearing southern
California. As the trough moves away from the area, the global
models predict that a ridge will rebuild to the north of Sergio in
a couple of days. This should result in a turn toward the
west-northwest and west at 48 hours and beyond. The official track
forecast is close to the simple and corrected dynamical model
consensus predictions.
Hurricane Sergio Discussion Number 13
NWS National Hurricane Center Miami FL EP212018
900 AM MDT Tue Oct 02 2018
The cloud pattern of Sergio continues to become better organized on
satellite imagery. The hurricane has a very cold cloud-topped
central dense overcast, with a developing eye, surrounded by curved
banding features. The current intensity is set at 85 kt based on a
blend of subjective and objective Dvorak estimates. Sergio is
forecast to continue moving over warm waters, under moderate
vertical shear and within a moist mid-level airmass for the next
few days. Therefore, additional strengthening is likely, and Sergio
will probably become a major hurricane in a day or so. The official
intensity forecast is close to the latest model consensus, IVCN.
The hurricane has been moving westward at a slightly slower pace,
and the motion estimate is 270/11 kt. A mid-level ridge to the
north of the system will soon be eroding, due to a trough dropping
in from the northwest. This change in steering currents should
result in Sergio turning toward the west-northwest today followed
by a northwestward motion in 2-3 days. In the latter part of the
forecast period, the ridge builds back in, and this is likely to
cause the tropical cyclone to turn back toward the west. The NHC
track forecast is similar to the previous one and follows the
dynamical model consensus, TVCN, fairly closely.
Tropical Storm Sergio Special Discussion Number 1
NWS National Hurricane Center Miami FL EP212018
1030 AM CDT Sat Sep 29 2018
Satellite imagery indicates that convection associated with the low
pressure area south-southwest of Acapulco has continued to become
better organized, with the low-level center embedded under the
convective overcast and near a developing complex of bands in the
southeastern semicircle. Based on this and continuity from earlier
scatterometer data, advisories are being initiated on Tropical
Storm Sergio with 35 kt winds.
Sergio is expected to be in an environment of light vertical shear
and high humidity, and over warm sea surface temperatures for the
next 3 days or so, which should result in steady strengthening. Near
the end of the forecast period, the storm may encounter increasing
northeasterly shear which could limit intensification. The intensity
forecast, which is near the intensity consensus, calls for steady
strengthening through 96 h, with Sergio becoming a hurricane by 48
h.
The initial motion is a somewhat uncertain 285/11. Sergio should
be steered generally westward for the next three days or so by the
subtropical ridge over Mexico. After that time, the cyclone should
approach a weakness in the ridge caused by a large mid- to
upper-level trough over California, and this should lead to a turn
toward the northwest. The track guidance is in good agreement
with this scenario, and the forecast track lies near the HCCA
corrected consensus model.
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