WPAC: DORA - Post-Tropical - Discussion

[cycloneye]

EP, 05, 2023081100, , BEST, 0, 129N, 1738W, 105, 961, HU

[cycloneye]

Flash strikes at eyewall. Making the last hurrah?

[cycloneye]

Phillippe Papín explains in this twitter thread about Dora, High Pressure and the fires in Maui.
 https://twitter.com/pppapin/status/1689757464487395328




 https://twitter.com/pppapin/status/1689760702322323457




 https://twitter.com/WxTca/status/1689806972260900864




 https://twitter.com/WxTca/status/1689806972260900864

[Ntxw]

This is by no means a meteorological diagnosis, but anecdotal. If look back though, the higher winds were associated greatest in tandem with the two features together rather than isolated alone before and after. We have ridges over the US all the time equally as strong that don't always feature high winds and fires. But as a noted example before something like this happened in Texas back in 2011 with lee. It isn't really Dora's windfield, but rather the gradient between the low pressure and high pressure. A nudge better than either feature alone.

[Sciencerocks]

[cycloneye]

Hurricane Dora Discussion Number 43
NWS Central Pacific Hurricane Center Honolulu HI EP052023
500 PM HST Thu Aug 10 2023

Dora has maintained a well-defined eye today, overcoming what
appears to be slightly restricted outflow aloft within its eastern
quadrant at times. The satellite presentation has changed little
through the day, and all fix agencies gave a FT and current
intensity of 5.5/102 kt, while CIMSS ADT rose to 107 kt just after
0000 UTC. Given the steady appearance, the initial intensity of Dora
has been held at 105 kt for this advisory, which represents a blend
of the inputs.

The initial motion for this advisory is 290/17 kt. Dora continues
to move toward the west-northwest along the southwest flank of deep
high pressure to the north-northeast. This general motion will
continue through the next 24 to 36 hours, with the forecast track
following a tightly clustered guidance envelope. The forward motion
of Dora will slow between 36 and 60 hours as the hurricane
approaches a weakness in the ridge aloft produced by an upper level
trough to the northwest. From 72 to 96 hours, Dora is forecast to
remain on a similar slow west-northwest to track, followed by a turn
toward the north-northwest at 120 hours. Guidance spread increases
slowly from 36 to 60 hours, then significantly from 72 hours
onward, likely due to differences in the depth of the cyclone and
the strength of the upper level trough to the northwest. The
forecast track lies close to the TVCN near the middle of the
guidance envelope and has been changed little since the last
package.

Dora continues to exceed expectations regarding intensity, due to
its small size and an environment of light vertical wind shear and
relatively warm water of around 28C. Given this history, the
forecast holds Dora steady through the next 12 hours and remains
near the higher side of the guidance envelope in showing only slow
weakening through 36 hours. At 36 hours and beyond, the SHIPS
guidance shows a sharp increase in vertical wind shear, and steady
weakening is expected. The intensity guidance shows considerable
spread during this time of steady weakening, with the statistical
guidance showing a slower rate of weakening compared to much of the
dynamical models. The forecast closely follows the ICON from 36 to
96 hours and weakens Dora slightly more aggressively than the
consensus at 120 hours.


FORECAST POSITIONS AND MAX WINDS

INIT 11/0300Z 13.2N 174.6W 105 KT 120 MPH
12H 11/1200Z 14.1N 176.9W 105 KT 120 MPH
24H 12/0000Z 15.4N 179.8W 100 KT 115 MPH
36H 12/1200Z 16.6N 177.8E 90 KT 105 MPH
48H 13/0000Z 17.5N 175.5E 75 KT 85 MPH
60H 13/1200Z 17.9N 173.4E 65 KT 75 MPH
72H 14/0000Z 18.2N 171.3E 55 KT 65 MPH
96H 15/0000Z 19.3N 167.7E 45 KT 50 MPH
120H 16/0000Z 21.2N 166.1E 30 KT 35 MPH...POST-TROP/REMNT LOW

$$
Forecaster Wroe

[Yellow Evan]

Likely to peak for the final time in the next 12-24 hours before the TUTT impedes southwesterly flow on it. In the meantime, the TUTT is enhancing its poleward outflow, which can greatly benefit a compact system like this.

[cycloneye]

Hurricane Dora Discussion Number 44
NWS Central Pacific Hurricane Center Honolulu HI EP052023
1100 PM HST Thu Aug 10 2023

Hurricane Dora continues to maintain a small eye this evening,
similar to much of the day. All fix agencies agreed with a current
intensity of 5.5 correlating with a maximum estimated wind speed
of 102 kt. CIMSS ADT was 110 kt and AiDT was 103 kt just
after 0600 UTC. Given the steady appearance, the initial intensity
of Dora has been held at 105 kt for this advisory, which represents
a blend of the inputs.

The initial motion for this advisory is 285/17kt. Dora continues
to move toward the west-northwest along the southwest flank of deep
high pressure system. This general motion will continue through the
next 24 hours, with the forecast track following a tightly
clustered guidance envelope. The forward motion of Dora will
gradually slow down and turn more northwesterly through the next
several days as it approaches a weakness in the ridge aloft
produced by an upper level trough to the northwest. Guidance spread
increases slowly from 24 to 60 hours, then significantly from 72
hours onward, likely due to differences in the depth of the cyclone
and the strength of the upper level trough to the northwest. The
forecast track lies close to middle of the guidance envelope and
has been changed little since the last package.

Dora continues to exceed expectations regarding intensity, due to
its small size and an environment of light vertical wind shear and
relatively warm water of around 28C. Given this history, the
forecast holds Dora steady through the next 12 hours and remains
near the higher side of the guidance envelope in showing only slow
weakening through 36 hours. At 36 hours and beyond, the SHIPS
guidance shows a sharp increase in vertical wind shear. The
intensity guidance shows considerable spread during this time of
steady weakening, with the statistical guidance showing a slower
rate of weakening compared to much of the dynamical models. Offical
forecast represents a blend of the two forecast trends.


FORECAST POSITIONS AND MAX WINDS

INIT 11/0900Z 13.7N 176.3W 105 KT 120 MPH
12H 11/1800Z 14.8N 178.5W 105 KT 120 MPH
24H 12/0600Z 16.1N 178.9E 100 KT 115 MPH
36H 12/1800Z 17.1N 176.5E 90 KT 105 MPH
48H 13/0600Z 17.8N 174.3E 75 KT 85 MPH
60H 13/1800Z 18.1N 172.2E 65 KT 75 MPH
72H 14/0600Z 18.6N 170.2E 55 KT 65 MPH
96H 15/0600Z 19.7N 167.2E 45 KT 50 MPH
120H 16/0600Z 21.4N 165.5E 30 KT 35 MPH...POST-TROP/REMNT LOW

$$
Forecaster Foster/Birchard

[Sciencerocks]

[cycloneye]

EP, 05, 2023081112, , BEST, 0, 142N, 1771W, 100, 965, HU

[Kingarabian]

This is by no means a meteorological diagnosis, but anecdotal. If look back though, the higher winds were associated greatest in tandem with the two features together rather than isolated alone before and after. We have ridges over the US all the time equally as strong that don't always feature high winds and fires. But as a noted example before something like this happened in Texas back in 2011 with lee. It isn't really Dora's windfield, but rather the gradient between the low pressure and high pressure. A nudge better than either feature alone.

https://i.imgur.com/77kXbNt.gif

Yeah agree here. Dora's size was too small to increase the winds over the islands by itself. But without it, the gradient wouldn't be this pronounced and likely means the trade winds wouldn't have been as strong.

[Kingarabian]

I get simply removing Dora's vort from the charts and seeing what the difference in wind speed is. But who is to say that Dora did not pump the ridge (It was practically a cat.4 the majority of its life time) as they both moved west in tandem. Eventually resulting in stronger than normal trade winds over the islands.

[cycloneye]

Hurricane Dora Discussion Number 45
NWS Central Pacific Hurricane Center Honolulu HI EP052023
500 AM HST Fri Aug 11 2023

Hurricane Dora maintained a small eye through most of the night,
but it has since mostly filled in. Infrared satellite shows the
southwest sector of the cyclone degrading as it is slowly moving
into an area of higher southerly shear. Dvorak current intensity
estimates of 5.5 from PHFO and SAB correlates with a maximum
estimated wind speed of 102 kt, with no change since the previous
advisory. CIMSS ADT was 97 kt and AiDT was 89 kt just after 1200
UTC. The initial intensity of Dora has been decreased slightly to
100 kt to account for the satellite appearance.

The initial motion for this advisory is 290/17kt. Dora continues to
move toward the west-northwest along the southwest flank of a deep
high pressure system. This general motion will continue through the
next 24 hours, with the forecast track following a tightly clustered
guidance envelope. The forward motion of Dora will gradually slow
down and turn more northwesterly through the next several days as
it approaches a weakness in the ridge aloft produced by an upper
level trough to the northwest. The forecast track has been adjusted
slightly north of the previous forecast after 24 hours, then a bit
more northeast after 60 hours to keep closer in line with model
consensus TVCE.

The intensity forecast for Dora shows a gradual decrease in maximum
winds through the next 36 hours, then a slightly faster decrease
through 5 days when it becomes post-tropical. The SHIPS guidance
shows a sharp increase in vertical wind shear after 24 hours. The
intensity guidance shows considerable spread during this time of
steady weakening, with the ECMWF weakening quickly and the GFS
holding onto the intensity through the next 5 days. Official
forecast represents a blend of the two forecast trends.

Dora is expected to move into the western Pacific as a typhoon
later today. This will make Dora only the second tropical cyclone
on record to reach/maintain hurricane strength in the eastern,
central and western Pacific. Although Dora of 1999 almost completed
this feat, the only other tropical cyclone known to do this was
Hurricane John in 1994.


FORECAST POSITIONS AND MAX WINDS

INIT 11/1500Z 14.5N 178.1W 100 KT 115 MPH
12H 12/0000Z 15.7N 180.0E 95 KT 110 MPH
24H 12/1200Z 16.9N 177.5E 90 KT 105 MPH
36H 13/0000Z 17.8N 175.2E 85 KT 100 MPH
48H 13/1200Z 18.3N 173.0E 70 KT 80 MPH
60H 14/0000Z 18.7N 171.1E 65 KT 75 MPH
72H 14/1200Z 19.4N 169.4E 55 KT 65 MPH
96H 15/1200Z 21.0N 167.2E 45 KT 50 MPH
120H 16/1200Z 23.5N 166.2E 30 KT 35 MPH...POST-TROP/REMNT LOW

$$
Forecaster Foster/Birchard

[CyclonicFury]

From high chance NATL invest to typhoon...Dora has been quite the explorer

[Yellow Evan]

Last 2 GFS runs now have Dora beating back the TUTT.

[Sciencerocks]

[cycloneye]

After many days as cat 3-4 and maybe 5, it goes down to cat 2.

EP, 05, 2023081118, , BEST, 0, 148N, 1786W, 95, 968, HU

[Kingarabian]

Shifting back into an intense curved band. Could have one more peak left in her.

[Sciencerocks]

[Sciencerocks]

 https://twitter.com/135knots/status/1690094548003741697