EPAC: GILMA - Post-Tropical - Discussion

[NDG]

Gilma still looks fairly healthy despite its satellite presentation during the past 24 hrs or so.

[cycloneye]

Hurricane Gilma Discussion Number 25
NWS National Hurricane Center Miami FL EP072024
500 AM HST Sat Aug 24 2024

Gilma continues to show a well-defined, but somewhat asymmetric,
central dense overcast in satellite imagery. AMSR microwave data
near 1000 UTC showed an eye and eyewall are still present under the
overcast, and the eye makes occasional attempts to appear in
infrared imagery. The various subjective and objective intensity
estimates currently have a wide range from 65-90 kt. However, the
overall trend of these estimates is down, and based on this the
initial intensity is reduced to a somewhat uncertain 80 kt.

The initial motion is 275/8 kt. A mid-level ridge is forecast to
gradually build to the north of Gilma during the next several days,
and this should steer the cyclone on a generally westward, or just
north of westward, track through the forecast period. The guidance
has shifted south since the last advisory, continuing a trend that
started yesterday. Based on this guidance, the new forecast track
is also adjusted a little south of the previous track.

Gilma is expected to remain over sea surface temperatures (SSTs)
near 26C for the next day or two, and since it is in a light shear
environment, only slow weakening is expected during this time.
After that time, increasing westerly shear and dry air entrainment
is likely to lead to significant weakening, even though the SSTs
along the forecast track remain near 25-26C. While this is the most
likely scenario, some differences have developed in the intensity
guidance. The global models and the HMON regional model generally
show Gilma degenerating to a post tropical cyclone by 96 h and to a
remnant low by 120 h. On the other hand, the latest HWRF, HAFS-A,
and HAFS-B runs show the cyclone remaining a convection producing
tropical storm through the end of the forecast period. Given the
forecast shear and dry air, these forecasts look too strong, and the
new intensity forecast will follow the global model solutions of a
faster decay.

FORECAST POSITIONS AND MAX WINDS

INIT 24/1500Z 17.6N 130.0W 80 KT 90 MPH
12H 25/0000Z 17.7N 131.3W 80 KT 90 MPH
24H 25/1200Z 17.9N 133.1W 80 KT 90 MPH
36H 26/0000Z 18.1N 134.8W 75 KT 85 MPH
48H 26/1200Z 18.3N 136.6W 70 KT 80 MPH
60H 27/0000Z 18.5N 138.5W 60 KT 70 MPH
72H 27/1200Z 18.7N 140.6W 50 KT 60 MPH
96H 28/1200Z 19.3N 145.0W 35 KT 40 MPH...POST-TROPICAL
120H 29/1200Z 20.0N 149.5W 30 KT 35 MPH...POST-TROP/REMNT LOW

$$
Forecaster Beven

[Hurricane2022]

Likely this isn't only 80/977
95/965 would be more reasonable

[Hurricane2022]

Likely intensifying again.

[Kingarabian]

Eye on the past 5 BD frames. Supports an instantaneous T5.5-6.0 depending on how closed off the northern quads are.

[Kingarabian]

Surprisingly the eye is attempting to warm. Likely a major hurricane pushing cat.4. Will need a special advisory.

[Yellow Evan]

Convection gradually curling out of downshear and eye is warming. Major hurricane soon again?

[Hurricane2022]

Still becoming even better now but I really doubt that NHC will go anything above 90 kts. But it's very likely that Gilma is a major again.

[cycloneye]

Still becoming even better now but I really doubt that NHC will go anything above 90 kts. But it's very likely that Gilma is a major again.

No. EP, 07, 2024082418, , BEST, 0, 176N, 1305W, 85, 974, HU

[Yellow Evan]

EP, 07, 202408241710, 30, DPNT, IP, , 1762N, 13031W, , 2, 90, 1, 977, 1, MEAS, , , , , , , , , , , , , , W, CIMS, , , , , , , , , , , , , , , , , , , , , , , , , , , , , , CIMSS D-PRINT
EP, 07, 202408241740, 10, DVTS, CI, , 1770N, 13050W, , 1, 90, 2, 970, 2, DVRK, , , , , , , , , , , , , , E, TAFB, ERA, VI, 1, 5050 /////, , , GOES18, CSC, T,
EP, 07, 202408241740, 20, DVTO, I, , 1764N, 13037W, , 1, 84, 1, 972, 1, DVRK, , , , , , , , , , , , , , , CIMS, AUT, I, 48, 1, 48, 3, L, 53, -3, -67, EYE, R8, GOES18, ,
EP, 07, 202408241740, 30, DPNT, IP, , 1763N, 13038W, , 2, 89, 1, 975, 1, MEAS, , , , , , , , , , , , , , W, CIMS, , , , , , , , , , , , , , , , , , , , , , , , , , , , , , CIMSS D-PRINT

[Yellow Evan]

24/1801 UTC 17.7N 130.5W T5.5/5.5 GILMA -- East Pacific

[Kingarabian]

Still becoming even better now but I really doubt that NHC will go anything above 90 kts. But it's very likely that Gilma is a major again.

No. EP, 07, 2024082418, , BEST, 0, 176N, 1305W, 85, 974, HU

85Kts?? Everything else points to this being at least 100kts.

[Kingarabian]

Very abnormal hurricane in this region of the eastern Pacific. We would normally see an annular donut type with a warm CDO vs a pinhole eye surrounded by super cold tops.

[cycloneye]

Hurricane Gilma Discussion Number 26
NWS National Hurricane Center Miami FL EP072024
1100 AM HST Sat Aug 24 2024

Gilma has become better organized during the past few hours, with
the eye becoming more distinct and the eyewall convection becoming
colder and more symmetric. In response, the various satellite
intensity estimates have increased to the 90-105 kt range. Based
on that, the initial intensity is increased to 95 kt, and this
might be conservative. This intensification could be due to the
center passing near a tongue of warmer sea surface temperatures.

The initial motion remains 275/8 kt. A mid-level ridge is forecast
to gradually build to the north of Gilma during the next several
days, and this should steer the cyclone on a generally westward, or
just north of westward, track through the forecast period. The
track guidance has changed little since the last advisory, and
while there is some spread in the forward speed it is tightly
clustered in direction. The new forecast track therefore has
little change from the previous forecast.

In contrast to the track forecast, the intensity forecast and
guidance have significant changes. First, it is uncertain how long
the current re-intensification will last. The bulk of the
intensity guidance shows little additional strengthening, but given
that the organization is still increasing some additional
strengthening is possible in the next 6-12 h. Second, there have
been some changes to the guidance in the 3-5 day period. The
regional hurricane models are forecasting lower intensities than
they did 6 h ago, with only the HAFS-A still keeping Gilma a
tropical storm at 120 h. On the other hand, simulated satellite
imagery from the GFS/ECMWF suggests that the cyclone will continue
to develop organized convection for a longer time than the previous
model runs were forecasting. Putting all of these changes together,
the new intensity forecast calls for a stronger Gilma during the
first 60 h, and now calls for the cyclone to retain tropical storm
status through 96 h. By 120 h, westerly shear and dry air
entrainment should cause the system to degenerate to a remnant low
pressure area.


FORECAST POSITIONS AND MAX WINDS

INIT 24/2100Z 17.7N 130.9W 95 KT 110 MPH
12H 25/0600Z 17.8N 132.2W 95 KT 110 MPH
24H 25/1800Z 18.0N 133.9W 85 KT 100 MPH
36H 26/0600Z 18.2N 135.7W 75 KT 85 MPH
48H 26/1800Z 18.4N 137.5W 70 KT 80 MPH
60H 27/0600Z 18.6N 139.5W 60 KT 70 MPH
72H 27/1800Z 18.9N 141.6W 55 KT 65 MPH
96H 28/1800Z 19.5N 145.8W 40 KT 45 MPH
120H 29/1800Z 20.2N 150.3W 30 KT 35 MPH...POST-TROP/REMNT LOW

$$
Forecaster Beven

[Hurricane2022]

Gilma is on the way to becoming a C4.

[aspen]

Gilma is on the way to becoming a C4.
https://imageshack.com/i/poTVrkOoj

Clearly trying again, although I suspect it’ll operationally fall short again.

[Kingarabian]

Incoming Cat 5? Eye is clearing out.

[cycloneye]

[Yellow Evan]

Very abnormal hurricane in this region of the eastern Pacific. We would normally see an annular donut type with a warm CDO vs a pinhole eye surrounded by super cold tops.

Shear vector doesn't favor annular hurricane formation.

[Yellow Evan]