EPAC: BLAS - Post-Tropical

[Kingarabian]

000
WTPZ43 KNHC 040854
TCDEP3

TROPICAL STORM BLAS DISCUSSION NUMBER 6
NWS NATIONAL HURRICANE CENTER MIAMI FL EP032016
300 AM MDT MON JUL 04 2016

During the past few hours, the satellite appearance of Blas has
changed from consisting of primarily a long curved band to a large
central dense overcast (CDO) feature. Recent AMSU data showed that a
nearly closed mid-level eye feature with a diameter of about 35 nmi
has also developed within the southwestern portion of the CDO. A
0420 UTC ASCAT pass revealed surface winds near 50 kt in the
northeastern quadrant and a radius of maximum winds of about 30 nmi.
UW-CIMSS ADT estimates were near 55 kt. These data support an
intensity of 55 kt at 0600 UTC. However, since that time the
satellite signature has improved, so the advisory intensity has
been increased to 60 kt.

The initial motion estimate remains a steady 285/10 kt. There is no
significant change to the previous forecast reasoning and the
latest NHC model guidance suite remains tightly packed. Therefore,
the new forecast track is essentially just an update of the
previous advisory track due to the subtropical ridge to the north of
Blas remaining strong throughout the entire forecast period. The
new NHC forecast closely follows the consensus model TVCE and
basically lies down the middle of the guidance envelope.

The atmospheric and oceanic environment is expected to be quite
favorable for Blas to strengthen during the next 48-60 hours. Since
the global models are forecasting Blas' outflow pattern to gradually
expand and become more symmetrical, along with the development of
both poleward and equator outflow channels, a period of rapid
intensification is expected for at least the next 24 hours. Blas is
expected to achieve its peak intensity around 48 hours or so when
the vertical wind shear is forecast to be low at around 5 kt. After
that, gradual weakening should begin by 72 hours when Blas will be
moving over sub-26C SSTs, creating cold upwelling/mixing beneath the
cyclone. The NHC intensity forecast is well above the consensus
model IVCN, and closely follows the LGEM statistical-dynamical
intensity model.

FORECAST POSITIONS AND MAX WINDS

INIT 04/0900Z 12.7N 113.2W 60 KT 70 MPH
12H 04/1800Z 13.2N 114.8W 70 KT 80 MPH
24H 05/0600Z 13.8N 117.4W 85 KT 100 MPH
36H 05/1800Z 14.2N 119.8W 95 KT 110 MPH
48H 06/0600Z 14.8N 122.1W 105 KT 120 MPH
72H 07/0600Z 16.1N 126.5W 100 KT 115 MPH
96H 08/0600Z 17.5N 130.3W 80 KT 90 MPH
120H 09/0600Z 19.4N 133.6W 55 KT 65 MPH

$$
Forecaster Stewart

[Kingarabian]

[stormwise]

2016JUL04 093000 4.3 987.2 72.2 4.3 4.3 4.4 MW ON OFF OFF -78.26 -76.40 UNIFRM N/A 31.8 12.72 113.28 FCST GOES15 29.2
2016JUL04 100000 4.4 985.5 74.6 4.4 4.4 4.4 MW ON OFF OFF -77.66 -76.75 UNIFRM N/A 31.8 12.74 113.37 FCST GOES15 29.1
2016JUL04 103000 4.4 985.5 74.6 4.4 4.4 4.4 MW ON OFF OFF -80.46 -77.72 UNIFRM N/A 31.8 12.77 113.45 FCST GOES15 29.1

Scene Type : UNIFORM CDO CLOUD REGION w/ MW EYE

Tops getting colder

[cycloneye]

12z Best Track up to Hurricane!

EP, 03, 2016070412, , BEST, 0, 129N, 1138W, 65, 994, HU, 64, NEQ, 20, 0, 0, 10, 1011, 250, 20, 0, 0, E, 0, , 0, 0, BLAS, D

[gatorcane]

Lots of deep convection. Blas is on its way to becoming a hurricane

[cycloneye]

First Hurricane of 2016 season.

BULLETIN
HURRICANE BLAS ADVISORY NUMBER 7
NWS NATIONAL HURRICANE CENTER MIAMI FL EP032016
900 AM MDT MON JUL 04 2016

...BLAS NOW A HURRICANE...
...EXPECTED TO STRENGTHEN FURTHER...


SUMMARY OF 900 AM MDT...1500 UTC...INFORMATION
----------------------------------------------
LOCATION...13.3N 114.4W
ABOUT 725 MI...1170 KM SSW OF THE SOUTHERN TIP OF BAJA CALIFORNIA
MAXIMUM SUSTAINED WINDS...75 MPH...120 KM/H
PRESENT MOVEMENT...WNW OR 285 DEGREES AT 13 MPH...20 KM/H
MINIMUM CENTRAL PRESSURE...994 MB...29.36 INCHES


HURRICANE BLAS DISCUSSION NUMBER 7
NWS NATIONAL HURRICANE CENTER MIAMI FL EP032016
900 AM MDT MON JUL 04 2016

Blas' cloud pattern consists of a large mass of cold-topped central
convection and a couple of fragmented outer bands. A 1027 UTC SSM/I
pass revealed a ragged mid-level eye feature, but the low-level
structure appeared less organized. Dvorak satellite classifications
were T4.0/65 kt and T4.5/77 kt from SAB and TAFB, respectively.
Taking into account the overnight ASCAT pass, the initial intensity
is set at 65 kt, the low end of the intensity estimates.

The initial motion estimate is unchanged at 285/11. The track
forecast remains straightforward. Blas is expected to be steered
along the southern side of a deep-layer subtropical ridge extending
westward from northern Mexico and the southern United States during
the next 3-4 days. The cyclone should reach the western periphery
of the ridge by days 4-5, which should result in a turn nearly
toward the northwest. The model guidance is in relatively good
agreement throughout the forecast period, though the GFS and ECMWF
models diverge some after day 3. The NHC track forecast does not
deviate much from the previous one and is north of the southernmost
ECMWF owing to the forecast of a strong hurricane, more like the GFS
solution indicates.

The large-scale environment surrounding Blas is characterized by
light to moderate northeasterly shear and a rich supply of
moisture. Coupled with warm-enough waters, Blas should intensify
into a large and intense hurricane during the next couple of days
once it establishes a better organized inner core. The NHC intensity
forecast continues to lean heavily on the statistical guidance, some
of which strengthens Blas even more than the current forecast.
Around 72 hours, even though the shear should still be low, the
hurricane should enter a drier and more stable environment and begin
traversing sub-26 deg C waters. This should promote a slow
weakening trend that will accelerate after 96 hours once Blas moves
over much cooler waters.



FORECAST POSITIONS AND MAX WINDS

INIT 04/1500Z 13.3N 114.4W 65 KT 75 MPH
12H 05/0000Z 13.6N 116.2W 75 KT 85 MPH
24H 05/1200Z 14.1N 118.7W 90 KT 105 MPH
36H 06/0000Z 14.6N 121.2W 105 KT 120 MPH
48H 06/1200Z 15.1N 123.5W 110 KT 125 MPH
72H 07/1200Z 16.3N 127.6W 95 KT 110 MPH
96H 08/1200Z 17.8N 131.3W 75 KT 85 MPH
120H 09/1200Z 19.8N 134.7W 50 KT 60 MPH

$$
Forecaster Kimberlain

[cycloneye]

 https://twitter.com/EricBlake12/status/749978608761004033

[Yellow Evan]

Inner core and CDO still not as organized as I would like.

[gatorcane]

Saved VIS loop, very symmetric and less dry air issues:

[Ntxw]

I think it's size is contributing to the more steady and slower pace strengthening. But it looks great though when everything consolidates and with an eye will be very picturesque major. Jimena last year was a sprawling strong storm on a similar path and raked up 40+ units of ACE. So we can probably expect 30-40 units from this one. in fact a lot of aspects with this system is nearly a carbon copy of Jimena last year I think...

[Yellow Evan]

Small dry slot early today is already being mixed out. Now the CDO needs to thicken or the eye needs to clear.

[tatertawt24]

Surprised this hasn't bombed out yet. It's just had 'that look' since yesterday.

[Yellow Evan]

Structure looking better on ASCAT but likely only 60-65 knots at best given the low bias of ASCAT.

[Kingarabian]

I don't think we use ASCAT to estimate a hurricanes true intensity since it can't show it properly. Only for establishing the wind radaii.

[cycloneye]

HURRICANE BLAS DISCUSSION NUMBER 8
NWS NATIONAL HURRICANE CENTER MIAMI FL EP032016
200 PM PDT MON JUL 04 2016

Blas' cloud pattern has not changed much in organization since this
morning, except for the emergence of what appears to be a ragged,
banding-type eye. The cyclone's central features are still not that
well organized, although there are some recent signs that this may
be changing. A dry slot of air has also been wrapping around the
western half of the circulation. Dvorak classifications remain T4.0
and T4.5 from SAB and TAFB, respectively. A 1652 UTC ASCAT overpass
indicates that Blas is a minimal hurricane at best, and the initial
intensity estimate is held at 65 kt for this advisory.

The latest fixes indicate that the initial motion is a little faster
and has a bit more of a northerly component than yesterday. The
best estimate is that the cyclone is moving 290/12. Overall, the
forecast reasoning is unchanged. Blas should be steered on a west-
northwestward course during the next several days to the south of
a strong, deep-layer subtropical ridge extending westward from
northern Mexico. A more northwesterly track is possible toward the
end of the forecast period as the cyclone nears the western end of
this ridge. The new NHC track forecast is adjusted a little to the
north in the short term and lies on the northern side of the
guidance envelope. The forecast does not deviate much from the
previous forecast beyond day 2 and lies near the multi-model
consensus.

It is unclear as to why Blas has not strengthened much, especially
since the large-scale environment appears conducive for
intensification. The current interruption to the cyclone's
strengthening could be related to a dry air intrusion from an
unknown source and/or some northeasterly shear. Whatever the cause,
additional strengthening is still indicated, and the new intensity
forecast remains near the upper-end statistical guidance. On days
3-4, Blas will reach the 26-deg sea surface temperature isotherm and
encounter substantially drier and more stable air. This should
result in gradual weakening in an otherwise low-shear environment.
By 96 hours, rapid weakening is expected to commence due to
increasingly unfavorable environmental factors.

The wind radii have been significantly adjusted based on the
aforementioned ASCAT overpass.

FORECAST POSITIONS AND MAX WINDS

INIT 04/2100Z 13.7N 115.7W 65 KT 75 MPH
12H 05/0600Z 14.1N 117.5W 75 KT 85 MPH
24H 05/1800Z 14.6N 120.0W 95 KT 110 MPH
36H 06/0600Z 15.1N 122.5W 105 KT 120 MPH
48H 06/1800Z 15.6N 124.6W 100 KT 115 MPH
72H 07/1800Z 16.8N 128.6W 80 KT 90 MPH
96H 08/1800Z 18.2N 131.7W 60 KT 70 MPH
120H 09/1800Z 20.0N 135.1W 35 KT 40 MPH...POST-TROPICAL

$$
Forecaster Kimberlain

[cycloneye]

 https://twitter.com/Adriansweather/status/750077892625768448

[alan1961]

Straight over Hurricane Blas with a little camera adjustment

[Kingarabian]

Looks like it's going to have a rather large eye if it manages to clear it out.

[gatorcane]

saved IR loop. It looks great. Notice the deep convection firing now near the center:

[Kingarabian]