Jul 22 Saturday 2017

Tropical Report

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
800 AM EDT Sat Jul 22 2017

For the North Atlantic…Caribbean Sea and the Gulf of Mexico:

Tropical cyclone formation is not expected during the next 5 days.

$$
Forecaster Avila

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
500 AM PDT Sat Jul 22 2017

For the eastern North Pacific…east of 140 degrees west longitude:

The National Hurricane Center is issuing advisories on Tropical
Storm Greg, located several hundred miles southwest of the southern
tip of the Baja California peninsula, and on Tropical Depression
Nine-E, located several hundred miles south of eastern Mexico.

1. A low pressure system is centered about 600 miles south-southwest of
the southern tip of the Baja California peninsula. Showers and
thunderstorms have increased overnight and, if this trend continues,
advisories will be initiated on a tropical depression later this
morning. Environmental conditions are forecast to be conducive for
development during the next couple of days while the system moves
generally westward at around 10 mph.
* Formation chance through 48 hours…high…90 percent.
* Formation chance through 5 days…high…90 percent.

Public Advisories on Tropical Depression Nine-E are issued under WMO
header WTPZ34 KNHC and under AWIPS header MIATCPEP4.
Forecast/Advisories on Nine-E are issued under WMO header
WTPZ24 KNHC and under AWIPS header MIATCMEP4.

Forecaster Blake

Tropical Depression Nine-E Discussion Number 4
NWS National Hurricane Center Miami FL EP092017
400 AM CDT Sat Jul 22 2017

The satellite appearance of the depression hasn’t changed much
during the past 6 hours, and the intensity remains 30 kt based on
an average of Dvorak estimates from TAFB, SAB, and the UW-CIMSS
ADT. Most of the convection is still removed from the center and
limited to the western half of the circulation. That said, the
intensity forecast thinking hasn’t changed, and the environment is
still expected to support strengthening throughout the forecast
period. Given the current structure of the storm, significant
intensification doesn’t seem imminent. However, looking at the
medium-term, the SHIPS-RII probability of an increase of 65 kt in 72
hours is up to 44 percent. The new intensity forecast is a little
lower than the previous forecast for the first 48 h, but similar
after that. The forecast remains above all of the guidance for the
first two days, and near the SHIPS model after that.

The initial motion is 285/11 kt. A mid-level ridge extending from
the Gulf of Mexico to western Mexico is the primary steering
feature for next few days, and the models are in good agreement on
a steady northwestward track beginning later today. All of the
global models depict the ridge strengthening after about 72 h, but
the extent to which the cyclone responds by turning toward the west
varies somewhat. In the models with a stronger vortex, most notably
the GFS, a weak upper-level low prevents the storm from turning too
sharply toward the west. A weaker modeled storm, as depicted in the
UKMET and HWRF would turn almost due west. Overall, the guidance
has shifted a little to the west for this advisory, so the forecast
has been nudged in that direction. It now lies on the right side of
the envelope, favoring the stronger solution of the GFS.

FORECAST POSITIONS AND MAX WINDS

INIT 22/0900Z 9.6N 96.6W 30 KT 35 MPH
12H 22/1800Z 10.1N 98.2W 35 KT 40 MPH
24H 23/0600Z 11.1N 100.1W 45 KT 50 MPH
36H 23/1800Z 12.1N 101.8W 55 KT 65 MPH
48H 24/0600Z 13.2N 103.4W 65 KT 75 MPH
72H 25/0600Z 15.1N 106.5W 85 KT 100 MPH
96H 26/0600Z 16.8N 109.9W 90 KT 105 MPH
120H 27/0600Z 18.0N 113.5W 95 KT 110 MPH

$$
Forecaster Zelinsky

Tropical Storm Greg Discussion Number 20
NWS National Hurricane Center Miami FL EP072017
200 AM PDT Sat Jul 22 2017

Microwave imagery indicates that the center of the tropical storm
is located to the south of the main area of deep convection. The
current intensity estimate is kept at 45 kt, based on a Dvorak
estimate from TAFB. Greg is being affected by southerly
shear associated with an upper-level low/trough located to the
north-northwest, which is clearly seen in water vapor imagery. The
global dynamical guidance indicates that the trough will lift
northward over the next day or two, resulting in a decrease of
shear. However, Greg is expected to reach slightly cooler waters
and begin to ingest drier mid-level air within a couple of days.
Therefore, only slight strengthening is anticipated, followed by
weakening later in the forecast period. By the end of the period,
the hostile environment should result in the system degenerating
into a remnant low. The official forecast is near or a little above
the intensity model consensus.

Greg is moving westward or 275/11 kt. A mid-level ridge to the
north of the tropical cyclone is likely to maintain the westward
motion for the next several days. In 4-5 days the ridge is
predicted to weaken somewhat, and this should result in a slowing
of the forward speed along with a turn toward the right. The
official track forecast is close to the simple and corrected
dynamical consensus tracks and is not too different from its
predecessor.

FORECAST POSITIONS AND MAX WINDS

INIT 22/0900Z 15.2N 123.1W 45 KT 50 MPH
12H 22/1800Z 15.3N 124.8W 45 KT 50 MPH
24H 23/0600Z 15.4N 127.2W 45 KT 50 MPH
36H 23/1800Z 15.3N 129.6W 50 KT 60 MPH
48H 24/0600Z 15.2N 131.6W 50 KT 60 MPH
72H 25/0600Z 15.7N 134.6W 45 KT 50 MPH
96H 26/0600Z 17.2N 137.0W 35 KT 40 MPH
120H 27/0600Z 18.0N 139.0W 25 KT 30 MPH…POST-TROP/REMNT LOW

$$
Forecaster Pasch