WPAC: DORA - Post-Tropical - Discussion

[SconnieCane]

El Nino years seem to always be good for at least one EPAC-CPAC crossover, even ones that are not "behaving" such as this one.

[Hurricane2022]

ERC is underway!

[cycloneye]

Hurricane Dora Discussion Number 28
NWS Central Pacific Hurricane Center Honolulu HI EP052023
1100 PM HST Sun Aug 06 2023

The satellite presentation of Dora remains impressive this evening
with a very warm 10 nautical mile wide eye surrounded by a very cold
dense overcast. The latest subjective Dvorak current intensity
estimates from PHFO, SAB, and JTWC came in at 6.0 (115 kt), 6.5 (127
kt), 6.5 (127 kt) respectively, while the objective Dvorak ADT and
AiDT estimates from UW-CIMSS were both 6.0 (115 kt). Using a blend
of these data, the initial intensity is set at 120 kt.

Dora is moving slightly south of due west at 20 kt. This general
motion is expected to continue during the next several days as a
deep layer ridge builds to the north of the Hawaiian Islands. A
turn to the northwest is forecast beyond day 3 as the tropical
cyclone rounds the southwestern periphery of the deep layer
subtropical ridge to the north of Hawaii. On this forecast track,
Dora is expected to move into the western Pacific basin late this
week. The forecast track has changed little from the previous
advisory and is roughly a blend of the HCCA and TVCN consensus
guidance and deterministic GFS and ECMWF guidance.

The environmental conditions along the forecast track of Dora during
the next several days are generally conducive for maintenance of a
very intense tropical cyclone, with the exception of the mid-level
dry air surrounding the system. Vertical wind shear will remain low
during the next 4 days, while sea surface temperatures remain around
27C. Beyond day 4 the SSTs increase into the 28/29C range, but
vertical wind shear is forecast to rise substantially. Given the
current annular appearance of Dora, the intensity forecast calls
for a very slow and steady decrease through the forecast period,
with the tropical cyclone being influenced primarily by the dry
mid-level environment surrounding the system. This forecast is
essentially a blend of the statistical and dynamical intensity
guidance and very close to the previous intensity forecast through
day 3, and slightly higher at days 4 and 5.


FORECAST POSITIONS AND MAX WINDS

INIT 07/0900Z 12.5N 146.3W 120 KT 140 MPH
12H 07/1800Z 12.4N 149.1W 115 KT 130 MPH
24H 08/0600Z 12.3N 152.9W 110 KT 125 MPH
36H 08/1800Z 12.2N 156.8W 105 KT 120 MPH
48H 09/0600Z 12.3N 160.7W 95 KT 110 MPH
60H 09/1800Z 12.5N 164.4W 90 KT 105 MPH
72H 10/0600Z 12.9N 168.0W 90 KT 105 MPH
96H 11/0600Z 14.5N 175.5W 80 KT 90 MPH
120H 12/0600Z 16.5N 178.5E 70 KT 80 MPH

$$
Forecaster Jelsema

[Yellow Evan]

A bit surprised this managed to wrap around a full band that is now the outer eyewall given the environment.

[cycloneye]

EP, 05, 2023080712, , BEST, 0, 124N, 1473W, 115, 953, HU

[Sciencerocks]

[cycloneye]

Hurricane Dora Discussion Number 29
NWS Central Pacific Hurricane Center Honolulu HI EP052023
500 AM HST Mon Aug 07 2023

The satellite presentation of Dora has degraded some overnight
with the convective ring of cold dense overcast warming slightly.
This is likely due to the ingestion of some drier mid-level air and
possibly going through an eyewall replacement cycle. The latest
subjective Dvorak current intensity estimates from PHFO, SAB, and
JTWC came in at 6.0 (115 kt), 6.5 (127 kt), 6.0 (115 kt)
respectively, while the objective Dvorak ADT and AiDT estimates from
UW-CIMSS were 105 kt and 109 kt. Using a blend of these data, the
initial intensity is lowered to 115 kt with this advisory.

Dora is moving slightly south of due west at 20 kt. This general
motion is expected to continue during the next several days as a
deep layer ridge builds to the north of the Hawaiian Islands. A turn
to the northwest is forecast beyond day 3 as the tropical cyclone
rounds the southwestern periphery of the deep layer subtropical
ridge to the north of Hawaii. On this forecast track, Dora is
expected to move into the western Pacific basin late this week. The
forecast track is virtually a carbon copy of the previous advisory
and is roughly a blend of the HCCA and TVCN consensus guidance and
deterministic GFS and ECMWF guidance.

The environmental conditions along the forecast track of Dora are
generally conducive for maintenance of a very intense tropical
cyclone during the next several days, with the exception of the mid-
level dry air surrounding the system. Vertical wind shear will
remain low during the next 4 days, while sea surface temperatures
remain around 27C through around day 3. From day 3 onward, the SSTs
increase into the 28/29C range, with vertical wind shear rising
substantially by day 5. Although the satellite presentation of Dora
has degraded slightly overnight, the continued annular appearance
should prevent a rapid weakening of the system, and the official
intensity forecast calls for a very slow and steady weakening trend
during the next couple days. Beyond 48 hours, a slight increase in
sea surface temperatures and ocean heat content may allow for some
intensification of the tropical cyclone. As a result, the official
intensity forecast has been increased slightly for days 3 and 4,
with a rather sharp decrease in intensity shown by day 5 as
increasing vertical wind shear should begin overwhelming Dora. This
forecast is essentially a blend of the statistical and dynamical
intensity guidance.


FORECAST POSITIONS AND MAX WINDS

INIT 07/1500Z 12.4N 148.3W 115 KT 130 MPH
12H 08/0000Z 12.2N 151.2W 110 KT 125 MPH
24H 08/1200Z 12.0N 154.9W 105 KT 120 MPH
36H 09/0000Z 12.0N 158.8W 100 KT 115 MPH
48H 09/1200Z 12.2N 162.7W 100 KT 115 MPH
60H 10/0000Z 12.6N 166.4W 100 KT 115 MPH
72H 10/1200Z 13.1N 170.0W 100 KT 115 MPH
96H 11/1200Z 15.0N 177.0W 90 KT 105 MPH
120H 12/1200Z 17.0N 177.0E 65 KT 75 MPH

$$
Forecaster Jelsema

[Ntxw]

Some structural changes and/or dry air issues? I'd say 105kts.

[Ntxw]

Did some recovery and uniform again with colder tops.

[cycloneye]

EP, 05, 2023080718, , BEST, 0, 123N, 1493W, 115, 953, HU

[Yellow Evan]

Eye is WMG but overall looks more fragile compared to yesterday.

[Hurricane2022]

ERC is finishing.

[cycloneye]

Hurricane Dora Discussion Number 30
NWS Central Pacific Hurricane Center Honolulu HI EP052023
1100 AM HST Mon Aug 07 2023

Dora remains far to the southeast of Hawaii this morning. Its
westward track will have it pass far south of Hawaii, posing no
direct threat to the islands. Satellite presentation shows
that Dora has undergone some minor changes in the last several
hours, but remains a compact and symmetric hurricane. The
subjective Dvorak estimates from PHFO, SAT and JTWC all came in at
6.0, and the objective estimates ranged from 110 to 120 kt. These
estimates, combined with a 1644Z SSMI pass showing a closed eye
wall, supports our initial intensity of 115 kt.

The model track guidance remains tightly clustered, particularly
through day 4, continuing high confidence in Dora's expected path.
The forecast track makes little change from the previous advisory
during this time. Beyond day 4, the forecast track has been nudged
a bit south to bring the track closer to the latest guidance. The
forecast track maintains a westward movement for the next several
days, before gaining latitude and then crossing the dateline
between days 4 and 5.

Minor fluctuations in intensity are still expected with Dora for
the next 36 hours or so, with Dora's environment remaining largely
unchanged. Dora is currently over 27 C waters, but is expected to
move over slightly warmer waters (28-29 C) around day 3. Shear in
the immediate area remains negligible in the short term, but on the
projected path, shows signs of increasing around day 4. The bigger
question relates to the amount of dry air that will be ingested into
Dora. At the moment, Dora sits just south of a very dry air mass.
The deterministic GFS and ECMWF models suggest mid level drier air
will be ingested into the system in the coming days, and will
likely contribute to the gradual weakening of Dora.


FORECAST POSITIONS AND MAX WINDS

INIT 07/2100Z 12.3N 150.2W 115 KT 130 MPH
12H 08/0600Z 12.0N 153.0W 110 KT 125 MPH
24H 08/1800Z 12.0N 156.6W 105 KT 120 MPH
36H 09/0600Z 12.1N 160.2W 100 KT 115 MPH
48H 09/1800Z 12.5N 164.1W 100 KT 115 MPH
60H 10/0600Z 13.0N 167.8W 95 KT 110 MPH
72H 10/1800Z 13.7N 171.6W 95 KT 110 MPH
96H 11/1800Z 15.6N 178.6W 85 KT 100 MPH
120H 12/1800Z 17.5N 175.5E 70 KT 80 MPH

$$
Forecaster Birchard/M Ballard

[Ntxw]

That should give Dora close to 28.4 units. Will likely surpass 30 tomorrow.

[Yellow Evan]

I would watch for one more peak incoming in about 3 days assuming the ECMWF mid-level shear environment verifies.

[Sciencerocks]

[cycloneye]

EP, 05, 2023080800, , BEST, 0, 121N, 1513W, 115, 953, HU

[cycloneye]

6.0.

TXPN27 KNES 072359
TCSCNP

A. 05E (DORA)

B. 07/2330Z

C. 12.2N

D. 151.2W

E. ONE/GOES-W

F. T6.0/6.0

G. IR/EIR/VIS

H. REMARKS...A WMG EYE SURROUNDED BY B AND EMBEDDED IN LG RESULTS IN
A DT 6.0 AFTER A +1.0 EYE ADJUSTMENT. THE MET AGREES BASED ON A SLOW
WEAKENING 24 HOUR TREND. THE PT ALSO AGREES. THE FT IS BASED ON THE DT.

I. ADDL POSITIONS

NIL


...BROWN

[Sciencerocks]

[Hurricane2022]