1. Disorganized showers and thunderstorms about 1000 miles south-
southwest of the southern tip of the Baja California peninsula are
associated with a broad area of low pressure. Environmental
conditions are expected to be generally conducive for development,
and this system is likely to become a tropical depression later this
week while moving westward at 15 mph.
* Formation chance through 48 hours...low...10 percent
* Formation chance through 5 days...high...70 percent
TROPICAL DEPRESSION NINE-E DISCUSSION NUMBER 1
NWS NATIONAL HURRICANE CENTER MIAMI FL EP092015
800 PM PDT WED JUL 29 2015
Satellite imagery and reports from NOAA buoy 51307 indicate that
the large low pressure area well southwest of the southern tip of
the Baja California has a closed circulation and sufficient
convection to be considered a tropical depression. Thus, advisories
are being initiated on Tropical Depression Nine-E. The initial
intensity is set at 30 kt, which could be conservative given the
current convective organization.
The initial motion is 280/13. For the next three days or so, a
strong low- to mid-level ridge north of the cyclone should steer it
generally west-northwestward, and the forecast track is in the
center of the guidance envelope during this period. From 72-120
hours, the dynamical models suggest a mid- to upper-level trough
should weaken the ridge to the northeast of the Hawaiian Islands.
The guidance becomes somewhat divergent during this time, with the
GFS and ECMWF models showing a more northward motion, while the
Canadian, UKMET, HWRF, and NAVGEM models show a continued
west-northwestward motion. The track forecast follows the GFS/ECMWF
solutions in calling for a turn toward the northwest and a decrease
in forward speed.
The depression is over warm sea surface temperatures and is expected
to remain in a moist environment with light vertical wind shear for
the next 72 hours or so. This should allow for steady
strengthening, and the forecast follows the intensity consensus in
calling for the cyclone to become a tropical storm in 12 hours and a
hurricane in about 48 hours. After 72 hours, a combination of
decreasing sea surface temperatures along the forecast track and
westerly shear is expected to cause the cyclone to weaken.
HURRICANE GUILLERMO DISCUSSION NUMBER 11
NWS NATIONAL HURRICANE CENTER MIAMI FL EP092015
800 AM PDT SAT AUG 01 2015
The cloud pattern is not as impressive as it was yesterday when
there was a hint of an eye on satellite imagery. However, Dvorak
T-numbers from all agencies still support an initial intensity of 90
kt. It appears that Guillermo has already peaked in intensity, and
the hurricane is heading toward an environment no longer favorable
for strengthening. On this basis, the NHC forecast calls for a
steady state during the next 12 hours or so, and a gradual weakening
thereafter. By the time Guillermo approaches the Hawaiian
Islands, the upper-level winds are forecast to be even more
unfavorable, and by then, Guillermo is expected to have weakened to
a tropical storm. The NHC forecast is very close to the intensity
consensus model ICON.
The steering currents have begun to weaken, and Guillermo is slowing
down. The best estimate of the initial motion is toward the west or
280 degrees at 12 kt. The hurricane is already located on the
southwestern edge of the subtropical ridge, and there is a large
weakness of the ridge to its northwest. This pattern should force
the cyclone to slow down even further and turn more to the
west-northwest. The GFS insists on a more northwesterly component
bringing the center of Guillermo north of the Hawaiian Islands. The
ECMWF, on the other hand, brings the cyclone south or near the
Islands. The NHC forecast is very similar to the previous one,
and is basically on top of the consensus of the ECMWF and the GFS
models.
Due to uncertainties in longer-range track predictions, it is
important for users not to focus on the exact track forecasts at 96
and 120 hours. Given the large spread of the models beyond 72
hours in this case, the forecast uncertainty is particularly high at
those time periods.
1. The National Hurricane Center in Miami, Florida is issuing advisories on hurricane Guillermo, located 1245 miles east-southeast of Hilo, Hawaii, under AWIPS header tcpep4 and WMO header wtpz34 KNHC. Guillermo is expected to cross 140°W into the Central Pacific Hurricane Center area of responsibility later today.
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