Jul 26 Wednesday 2017

Tropical Report

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
800 AM EDT Wed Jul 26 2017

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

1. A few showers and thunderstorms south of the Cabo Verde Islands
are associated with a tropical wave moving westward at 10 to 15
mph. Development of this system, if any, will be slow to occur.
* Formation chance through 48 hours…low…near 0 percent.
* Formation chance through 5 days…low…20 percent.

Forecaster Avila

Tropical Weather Outlook
Tropical Weather Outlook
NWS National Hurricane Center Miami FL
500 AM PDT Wed Jul 26 2017

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

The National Hurricane Center is issuing advisories on Tropical
Depression Greg, located more than 1000 miles east of the Big Island
of Hawaii, on Hurricane Hilary, located several hundred miles south
of southern tip of the Baja California peninsula, and on Hurricane
Irwin, located several hundred miles west-southwest of the southern
tip of the Baja California peninsula.

1. An area of low pressure could form several hundred miles south of
Mexico in a day or two. Development, if any, of this system is
expected to be slow to occur during the next few days due to strong
upper-level winds. These winds might become more conducive for some
development this weekend as Hurricane Hilary moves farther away from
the disturbance. This system is expected to move west-northwestward
at 5 to 10 mph during the next several days.
* Formation chance through 48 hours…low…near 0 percent.
* Formation chance through 5 days…low…20 percent.

Forecaster Blake

Hurricane Hilary Discussion Number 21
NWS National Hurricane Center Miami FL EP092017
900 AM MDT Wed Jul 26 2017

Satellite images indicate that Hilary remains a powerful hurricane.
The central dense overcast has become more symmetric, although
convection is still preferentially forming in the eastern eyewall.
Any eye feature, however, is somewhat less distinct than a few hours
ago, and the latest microwave passes are again showing an open
eyewall on the west side. Intensity estimates range from 82 to 99
kt, so the initial wind speed will stay at 90 kt.

There are still hints of northerly shear in cirrus cloud motions
from the 1-min GOES-16 data, although the cyclone’s cloud canopy
looks less distorted than yesterday. This shear is forecast to
persist for the next day or two while the hurricane moves over
warm waters. After that time, while the shear could decrease,
Hilary will be traversing marginally warm waters, with some increase
in drier, more stable air in the environment. Most of the guidance
is in good agreement on little change in the short-term, with a
gradual decrease in wind speed through 3 days. Beyond then, much
colder waters should cause a more rapid weakening, along with some
interaction with Irwin. The new NHC forecast is basically an update
of the previous one and lies close to IVCN, the variable intensity
model consensus. It should be noted that the ECMWF is on its own by
intensifying Hilary to a major hurricane in 2 to 3 days.

The initial motion is 280/11. The track forecast is essentially
unchanged for the next 48 h, while Hilary is expected to be steered
by the mid-level subtropical ridge to the north. After that time,
the ridge is forecast to become weaker to due to a mid- to
upper-level trough dropping over the Baja California peninsula.
Models are not in good agreement on how much the ridge weakens due
to this trough, leading to a wide disparity of solutions at long
range. There has been little change in the guidance suite since 6z,
so the official forecast is close to the previous one.

FORECAST POSITIONS AND MAX WINDS

INIT 26/1500Z 16.4N 112.3W 90 KT 105 MPH
12H 27/0000Z 16.7N 113.9W 90 KT 105 MPH
24H 27/1200Z 17.1N 115.7W 90 KT 105 MPH
36H 28/0000Z 17.5N 117.4W 85 KT 100 MPH
48H 28/1200Z 18.1N 118.9W 80 KT 90 MPH
72H 29/1200Z 19.7N 121.9W 75 KT 85 MPH
96H 30/1200Z 21.4N 125.4W 55 KT 65 MPH
120H 31/1200Z 23.0N 129.0W 35 KT 40 MPH

$$
Forecaster Blake

Tropical Storm Irwin Discussion Number 17
NWS National Hurricane Center Miami FL EP102017
800 AM PDT Wed Jul 26 2017

Satellite images and microwave data indicate that Irwin’s cloud
pattern has significantly deteriorated since yesterday. It now
consists of a tight circulation center located just to the south of
an area of deep, but not too well organized, convection.
Consequently, the initial intensity has been decreased to 55 kt
based on lower Dvorak T-numbers from all agencies. The environment
does not support significant weakening, but is not favorable for
much intensification either. The NHC forecast calls for a slight
weakening today, and shows no change in intensity for the
next 5 days. Although the intensity forecast is a little bit
different from the previous one due to the lower current intensity,
it does not change the general trend expressed in previous NHC
forecasts.

Irwin is moving toward the west-southwest or 255 degrees at 6 kt.
Currently, the cyclone is embedded within weak steering currents,
and Irwin will probably continue on the same slow west-southwest
track during the next day or two. After that time, Hurricane Hilary
is forecast to pass well north of Irwin, and the steering currents
will change to southerlies, and most of the models agree that Irwin
should begin to move with a northerly component in the wake of
Hilary. This is reflected in the official NHC forecast which in fact
is close to the multi-model consensus TVCN, and is not very
different from the previous one.

FORECAST POSITIONS AND MAX WINDS

INIT 26/1500Z 15.6N 122.1W 55 KT 65 MPH
12H 27/0000Z 15.3N 123.0W 45 KT 50 MPH
24H 27/1200Z 14.9N 124.1W 45 KT 50 MPH
36H 28/0000Z 14.5N 125.0W 45 KT 50 MPH
48H 28/1200Z 14.5N 125.5W 45 KT 50 MPH
72H 29/1200Z 15.0N 125.0W 45 KT 50 MPH
96H 30/1200Z 17.5N 125.0W 45 KT 50 MPH
120H 31/1200Z 20.5N 126.0W 45 KT 50 MPH

$$
Forecaster Avila

Tropical Depression Greg Discussion Number 37
NWS Central Pacific Hurricane Center Honolulu HI EP072017
Issued By NWS National Hurricane Center Miami FL
500 AM HST Wed Jul 26 2017

Strong shear became established over Greg, and the cyclone now
consists of a tight swirl of low clouds with a few small patches of
deep convection. Initial intensity is 25 kt, and with increasing
shear and cool waters nearby, weakening should continue. Greg should
become a remnant low later today.

The depression is moving toward the west or 280 degrees at 10 kt
steered by the low-level trades, and this general motion should
continue until dissipation in a day or so.

FORECAST POSITIONS AND MAX WINDS

INIT 26/1500Z 18.1N 141.0W 25 KT 30 MPH
12H 27/0000Z 18.5N 142.5W 25 KT 30 MPH…POST-TROP/REMNT LOW
24H 27/1200Z 18.5N 144.0W 25 KT 30 MPH…POST-TROP/REMNT LOW
36H 28/0000Z 18.0N 146.0W 20 KT 25 MPH…POST-TROP/REMNT LOW
48H 28/1200Z…DISSIPATED

$$
Forecaster Avila