BULLETIN
Post-Tropical Cyclone Irwin Advisory Number 42
NWS National Hurricane Center Miami FL EP102017
200 PM PDT Tue Aug 01 2017
...IRWIN NOW A REMNANT LOW...
...THIS IS THE LAST ADVISORY...
SUMMARY OF 200 PM PDT...2100 UTC...INFORMATION
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LOCATION...26.6N 129.7W
ABOUT 1265 MI...2040 KM WNW OF THE SOUTHERN TIP OF BAJA CALIFORNIA
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/H
PRESENT MOVEMENT...NNW OR 330 DEGREES AT 8 MPH...13 KM/H
MINIMUM CENTRAL PRESSURE...1007 MB...29.74 INCHES
WATCHES AND WARNINGS
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There are no coastal watches or warnings in effect.
DISCUSSION AND 48-HOUR OUTLOOK
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At 200 PM PDT (2100 UTC), the center of Post-Tropical Cyclone Irwin
was located near latitude 26.6 North, longitude 129.7 West. The
post-tropical cyclone is moving toward the north-northwest near 8
mph (13 km/h), and this motion is expected to continue
today.
Maximum sustained winds are near 35 mph (55 km/h) with higher gusts.
Dissipation is expected during the next day or so.
The estimated minimum central pressure is 1007 mb (29.74 inches).
HAZARDS AFFECTING LAND
----------------------
None.
NEXT ADVISORY
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This is the last public advisory issued by the National Hurricane
Center on this system. For additional information on the remnant low
please see High Seas Forecasts issued by the National Weather
Service, under AWIPS header NFDHSFEPI, WMO header FZPN02 KWBC, and
on the web at http://www.opc.ncep.noaa.gov/shtml/NFDHSFEPI.shtml.
Tropical Storm Irwin Discussion Number 33
NWS National Hurricane Center Miami FL EP102017
800 AM PDT Sun Jul 30 2017
Even though Irwin is crossing the 26 deg C isotherm, it does not
appear to be weakening yet. In fact, recent microwave data indicate
the tropical storm has a mid-level eye, which has occasionally
appeared in geostationary satellite images. The system is still
producing a fair amount of deep convection, especially to the south
of the center. The latest Dvorak CI-numbers from TAFB and SAB are
3.5/55 kt and accordingly, the initial intensity is set a bit higher
to 55 kt. This wind speed estimate is also in agreement with ASCAT
data from several hours ago that showed maximum winds near 50 kt.
Despite the recent increase in intensity, Irwin is expected to begin
weakening soon as it moves over even cooler waters and into a drier
and more stable air mass. The storm is likely to become a remnant
low in 36 to 48 hours when it will be over SSTs near 22 deg C. Most
of the global models show the remnant low dissipating in 4 to 5
days. The NHC intensity forecast follows the trend of the guidance,
and it is largely unchanged from the previous prediction.
Irwin is moving north-northwestward, or 345 degrees, at 8 kt. The
system is embedded in south-southeasterly flow in the wake of
Hilary, and it is expected to remain in this steering flow for
another day or two. Once Irwin becomes a remnant low, the shallow
system is expected to turn a little to the left and slow down as it
becomes steered by the low-level flow. The NHC track forecast is
adjusted a little to the north and east of the previous one, to come
into better agreement with the latest consensus models.
Hurricane Irwin Discussion Number 12
NWS National Hurricane Center Miami FL EP102017
200 AM PDT Tue Jul 25 2017
Deep convection associated with Irwin now wraps almost all of the
way around the center, and there have been occasional hints of a
eye in microwave and conventional satellite imagery. Subjective
satellite estimates from TAFB and SAB are just below hurricane
strength, while several objective estimates, including the CIMSS
satellite consensus, are above hurricane strength. With the attempts
at eye formation, the initial intensity will lean toward the higher
intensity estimates, and thus Irwin is upgraded to a hurricane.
The initial motion is a little more northward than before at 300/4.
A slow westward motion is forecast today as a weak mid-level ridge
remains in place to the north of the storm. A west-southwestward
motion is expected between 24-72 h as Hurricane Hilary approaches
from the east. After that, Irwin is expected to undergo an binary
interaction with Hilary, with the most likely result for Irwin
being a generally northward motion around the eastern semicircle of
Hilary. The details of this are still uncertain, with the ECMWF
and Canadian models merging the two cyclones before 120 h, while
the GFS and UKMET keep them separate until after 120 h. The new
track forecast is similar to the previous forecast through 72 h.
After that, it leans towards the GFS/UKMET in keeping the cyclone
separate and accelerating Irwin around the eastern side of Hilary.
Little change in strength is likely for the next 24 h. After that,
increasing shear associated with the outflow of Hilary is likely to
cause Irwin to weaken, although there is considerable spread in the
guidance as to how much shear and how much weakening. By the end
of the forecast period, cooler water along the forecast track and
proximity to Hilary should cause additional weakening. The new
forecast track is a slight adjustment of the previous track. An
alternative intensity scenario is that Irwin dissipates as it is
absorbed by Hilary before 120 h.
Tropical Depression Ten-E Discussion Number 1
NWS National Hurricane Center Miami FL EP102014
900 AM MDT Sat Jul 22 2017
I thought there was no more room for another cyclone in the eastern
Pacific basin, but nature managed to produce another one. The
disturbance that NHC has been monitoring for several days has
finally developed enough circulation and convection to be classified
as a tropical depression, the sixth cyclone that has formed in the
month of July.
The center is located on the northern edge of a circular mass of
deep convection and, based of an average of Dvorak numbers, it is
being assigned an initial intensity of 30 kt. The depression is in
between TS Greg and TD 9-E, and the environment is not ideal for
strengthening. However, most of the global models show a decrease
of the shear in the next few days, and this will allow some
intensification.
The depression is trapped south of a subtropical ridge and is moving
toward the west at about 6 kt. The nose of the ridge is forecast to
amplify westward, and this flow pattern will likely force the
cyclone on a slow west and then west-southwest track during the next
five days. Most of the guidance agree with this solution, but one
must use caution since there could be some interaction with Tropical
Depression Nine-E which increases the forecast uncertainty.
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