Jul 29 Saturday 2017

Tropical Report

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
800 AM EDT Sat Jul 29 2017

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

1. A tropical wave that recently moved over the Cabo Verde Islands is
moving westward at 10 to 15 mph. Some development of this system is
possible next week while the wave moves across the tropical
Atlantic.
* Formation chance through 48 hours…low…near 0 percent.
* Formation chance through 5 days…low…20 percent.

Forecaster Avila

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
500 AM PDT Sat Jul 29 2017

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

The National Hurricane Center is issuing advisories on Tropical
Storm Hilary, located several hundred miles west of the southern tip
of the Baja California peninsula, and on Tropical Storm Irwin,
located about 1000 miles west-southwest of the southern tip of the
Baja California peninsula.

1. An area of low pressure is expected to form by the middle of next
week several hundred miles south of the southern coast of Mexico.
Conditions appear favorable for some development of this system
while it moves westward to west-northwestward at around 15 mph.
* Formation chance through 48 hours…low…near 0 percent.
* Formation chance through 5 days…low…30 percent.

Forecaster Zelinsky

Tropical Storm Hilary Discussion Number 32
NWS National Hurricane Center Miami FL EP092017
200 AM PDT Sat Jul 29 2017

The deep convection associated with Hilary has lost some
organization since the last advisory, with little or no convection
currently occurring over the western semicircle. Satellite
intensity estimates range from 45-65 kt, and recent ASCAT data
showed winds of at best 50 kt. Based on these, the initial
intensity is nudged down to a possibly generous 55 kt. The system
will be moving over progressively cooler water and into a more
stable environment, which should cause a steady weakening. By 48
hours, Hilary is forecast to become a remnant low over 23C waters,
and the cyclone is forecast to dissipate completely after 96 hr.

The initial motion is now 305/9. As mentioned in the previous
advisory, a mid-level ridge extending from southern California
west-southwestward across the eastern Pacific should steer Hilary
on this general path for the next couple of days. The forecast then
gets more complicated due to potential interaction with TS Irwin.
The guidance is in less good agreement than earlier, with the
possibilities ranging from the Canadian model merging the two
systems in 72 h to the ECMWF showing them dissipating in close
proximity to one another near 120 h. The track guidance suggests a
west-northwestward to westward turn for Hilary as Irwin or its
remnants move around the eastern and northern sides, and the
official forecast follows this scenario. The new forecast track is
similar to the previous track for the first 36-48 h and then is
nudged to the south thereafter.

FORECAST POSITIONS AND MAX WINDS

INIT 29/0900Z 20.7N 120.8W 55 KT 65 MPH
12H 29/1800Z 21.7N 122.3W 50 KT 60 MPH
24H 30/0600Z 22.9N 124.3W 40 KT 45 MPH
36H 30/1800Z 24.1N 126.6W 30 KT 35 MPH
48H 31/0600Z 24.9N 128.8W 25 KT 30 MPH…POST-TROP/REMNT LOW
72H 01/0600Z 25.5N 131.5W 25 KT 30 MPH…POST-TROP/REMNT LOW
96H 02/0600Z 25.5N 133.5W 20 KT 25 MPH…POST-TROP/REMNT LOW
120H 03/0600Z…DISSIPATED

$$
Forecaster Beven

Tropical Storm Irwin Discussion Number 28
NWS National Hurricane Center Miami FL EP102017
200 AM PDT Sat Jul 29 2017

Convection associated with Irwin has changed little over the past
several hours, with weak convection in ragged bands occurring
primarily in the southeastern semicircle. Satellite intensity
estimates have also changed little since the last advisory, so the
initial intensity remains 50 kt. Some strengthening is possible
today while the storm remains over warm sea surface temperatures.
After that, Irwin should weaken over waters that cool to near 23C
near the 96 h forecast position. As mentioned in the discussion
for Tropical Storm Hilary, the model guidance is diverse as to the
eventual fate of Irwin as it interacts with Hilary, with the
possibilities ranging from the early merger shown by the Canadian
model to the ECMWF scenario of the two systems dissipating
separately but in close proximity. The forecast leans more to the
ECMWF solution and shows Irwin dissipating after 96 h to the north
of Hilary or its remnants.

Irwin is currently nearly stationary. A northward motion is
expected to begin later today. Then, as the cyclone moves around
the eastern and northern side of Hilary, a turn toward the
north-northwest is expected in about 36 h, followed by a
northwestward motion near the end of the cyclone’s life. The new
forecast track is similar to the previous track through 48 h, and it
is shifted westward after that in agreement with the various
consensus models.

FORECAST POSITIONS AND MAX WINDS

INIT 29/0900Z 14.9N 124.9W 50 KT 60 MPH
12H 29/1800Z 15.7N 124.9W 55 KT 65 MPH
24H 30/0600Z 17.1N 125.1W 50 KT 60 MPH
36H 30/1800Z 19.2N 125.7W 45 KT 50 MPH
48H 31/0600Z 21.7N 127.0W 35 KT 40 MPH
72H 01/0600Z 25.5N 130.0W 25 KT 30 MPH…POST-TROP/REMNT LOW
96H 02/0600Z 27.5N 133.5W 20 KT 25 MPH…POST-TROP/REMNT LOW
120H 03/0600Z…DISSIPATED

$$
Forecaster Beven