Aug 16 Wednesday 2017

Tropical Report

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
800 AM EDT Wed Aug 16 2017

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

The National Hurricane Center is issuing advisories on Hurricane
Gert, located a few hundred miles northwest of Bermuda.

1. A low pressure system located about 900 miles east of the Lesser
Antilles continues to produce disorganized showers and a few
thunderstorms. This system is moving westward at 15 to 20 mph,
and it is expected to cross into the Caribbean Sea on Friday.
Upper-level winds are forecast to become a little more conducive
for development during the next several days, and interests in the
Lesser Antilles should monitor the progress of this system.
* Formation chance through 48 hours…low…30 percent.
* Formation chance through 5 days…medium…40 percent.

2. A second area of low pressure located several hundred miles west of
the Cabo Verde Islands is also producing disorganized showers and
thunderstorms. Gradual development of this system is possible
during the next few days before upper-level winds become less
conducive over the weekend. This system is expected to move
west-northwestward at 15 to 20 mph during the next several days.
* Formation chance through 48 hours…low…30 percent.
* Formation chance through 5 days…medium…40 percent.

3. A tropical wave near the west coast of Africa is producing a
large area of disorganized showers and thunderstorms.
Environmental conditions appear conducive for gradual development of
this wave while it moves westward to west-northwestward at about 15
mph during the next several days.
* Formation chance through 48 hours…low…near 0 percent.
* Formation chance through 5 days…medium…40 percent.

Forecaster Berg

GERT ACCELERATING NORTHEASTWARD OVER THE NORTHWESTERN ATLANTIC

Hurricane Gert Discussion Number 15
NWS National Hurricane Center Miami FL AL082017
1100 AM AST Wed Aug 16 2017

GOES-16 1-minute visible imagery has shown Gert’s eye coming and
going over the past several hours, and for the first time a
distinct warm spot has appeared in infrared images. However,
subjective Dvorak estimates are unchanged from six hours ago, and
the objective ADT has actually decreased a bit. The initial
intensity is therefore held at 80 kt. Gert has another 18-24 hours
before it reaches significantly colder waters north of the Gulf
Stream, so the cyclone still has the opportunity for a little more
strengthening later today and this evening. Southwesterly shear is
expected to begin increasing tonight, and the higher shear and
colder water should cause a steady weakening trend to begin on
Thursday. The global model fields indicate that Gert should be
fully extratropical, embedded in a frontal zone, within 48 hours,
and that is reflected in the official forecast. There is still a
lot of uncertainty regarding when Gert will be absorbed by another
larger extratropical cyclone, but most of the guidance tends to
agree that it should be absorbed by day 5 over the north Atlantic.

Gert’s forward speed continues to increase, and the hurricane is
now moving toward the northeast with a motion of 055/22 kt. Gert
is embedded in mid-latitude westerly flow between a mid-level high
centered east of Bermuda and a large cut-off low over eastern
Canada, and this pattern should force the cyclone on a fast
northeastward pace over the north Atlantic at least for the next 72
hours. A slower motion is forecast by day 4 once post-tropical
Gert interacts with the large cut-off low moving east of Atlantic
Canada. There was very little change in the latest track guidance,
and no significant deviations from the previous NHC forecast were
required on this cycle. The post-tropical portion of the track,
intensity, and wind radii forecasts incorporate guidance from NOAA’s
Ocean Prediction Center.

Swells from Gert are affecting portions of the mid-Atlantic coast of
the United States, and are expected to spread northward to New
England and Atlantic Canada during the next day or two. These
swells are likely to produce dangerous surf and rip current
conditions. Please consult products from your local weather forecast
office for more information.

FORECAST POSITIONS AND MAX WINDS

INIT 16/1500Z 37.4N 65.7W 80 KT 90 MPH
12H 17/0000Z 39.0N 61.3W 85 KT 100 MPH
24H 17/1200Z 41.8N 53.6W 75 KT 85 MPH
36H 18/0000Z 45.5N 45.2W 65 KT 75 MPH
48H 18/1200Z 49.5N 38.4W 50 KT 60 MPH…POST-TROP/EXTRATROP
72H 19/1200Z 55.0N 32.2W 40 KT 45 MPH…POST-TROP/EXTRATROP
96H 20/1200Z 55.0N 26.0W 40 KT 45 MPH…POST-TROP/EXTRATROP
120H 21/1200Z…ABSORBED BY A LARGER EXTRATROPICAL LOW

$$
Forecaster Berg

 Tropical Weather Outlook
Tropical Weather Outlook
NWS National Hurricane Center Miami FL
500 AM PDT Wed Aug 16 2017

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

1. A broad area of low pressure located several hundred miles south-
southwest of the southern tip of the Baja California peninsula is
producing limited shower and thunderstorm activity. Development, if
any, of this system is expected to be slow to occur while it moves
westward at 10 mph during the next several days.
* Formation chance through 48 hours…low…near 0 percent.
* Formation chance through 5 days…low…10 percent.

Forecaster Roberts