EPAC: DOUGLAS - Remnants

[bob rulz]

At least it made it to an official cat 4 before the ERC kicked in.

Would be surprised if the NHC didn't bump up its max intensity at least 5 if not 10 kts in post-analysis.

[Kingarabian]

Still maintaining, SAB came In with 5.5/6.0. ADT is at 5.9.

[Kingarabian]

Hurricane Douglas Discussion Number 16
NWS National Hurricane Center Miami FL EP082020
1100 PM HST Thu Jul 23 2020

Douglas continues to look impressive in satellite images, with a
clear eye and symmetric convection in all quadrants. Broad outflow
channels extend about 300 n mi in every direction from the cyclone,
indicative of nearly zero wind shear. The latest Dvorak CI values
from TAFB and SAB, as well as the recent UW/CIMSS ADT estimates
are all T6.0, which supports keeping the initial advisory intensity
at 115 kt.

Douglas is crossing the 26 C isotherm, and will continue to move
over relatively cooler waters of about 25 C over the next day or so.
This should cause the cyclone to begin weakening very soon. In about
48 h, Douglas is forecast to move back across the 26 C isotherm, but
at the same time the cyclone is forecast to begin encountering a
drier, more stable airmass and increasing vertical wind shear.
Despite the warmer waters, these other more hostile environmental
factors are expected to cause Douglas to gradually weaken for the
remainder of the 5-day forecast period. The latest NHC forecast is
changed little from the previous advisory, and is very close to a
blend of the corrected consensus HCCA and the IVCN/ICON consensus
aids.

Douglas is still moving quickly west-northwestward or 295/16 kt.
A mid-level ridge to the north of the cyclone should keep moving
the cyclone in the same general direction over the next couple of
days. Over the weekend, as Douglas approaches the Hawaiian Islands,
a more westward motion is forecast as another ridge builds to the
north of the cyclone. There is some notable spread in the model
guidance now compared to yesterday as Douglas approaches the
Hawaiian Islands. The faster and southernmost guidance from the
ECMWF takes the center of the cyclone over the big island, while the
northernmost GFS and HWRF take the cyclone just north of the island
chain. The other guidance, including the track consensus aids lie in
between those solutions. The latest NHC forecast was nudged
slightly northward between 48 h and 96 h, but still remains south
of the consensus aids during those time periods. Otherwise, the NHC
forecast was little changed from the previous one.

This is the last advisory issued by the National Hurricane Center
on Douglas. Future information on this system can be found in
Forecast/Advisories issued by the Central Pacific Hurricane Center
beginning at 1500 UTC under AWIPS header HFOTCMCP2 and WMO header
WTPA22 PHFO. For information specific to the Hawaiian Islands,
users should continue to consult products from the National Weather
Service Forecast Office in Honolulu, Hawaii, at www.weather.gov/hfo.


Key Messages:

1. Douglas is expected to move near or over portions of the
Hawaiian Islands this weekend, and there is an increasing chance
that strong winds, dangerous surf, and heavy rainfall could affect
portions of the state beginning Saturday night or Sunday.
Interests on the Hawaiian Islands should continue to monitor the
progress of Douglas and the official forecasts as they evolve over
the next few days. Watches could be issued on Friday.


FORECAST POSITIONS AND MAX WINDS

INIT 24/0900Z 15.7N 140.3W 115 KT 130 MPH
12H 24/1800Z 16.7N 142.6W 105 KT 120 MPH
24H 25/0600Z 17.9N 145.7W 95 KT 110 MPH
36H 25/1800Z 19.0N 148.7W 85 KT 100 MPH
48H 26/0600Z 19.9N 151.7W 75 KT 85 MPH
60H 26/1800Z 20.5N 154.5W 65 KT 75 MPH...NEAR HAWAII
72H 27/0600Z 21.0N 157.1W 60 KT 70 MPH...NEAR HAWAII
96H 28/0600Z 22.0N 163.2W 50 KT 60 MPH
120H 29/0600Z 22.4N 170.0W 45 KT 50 MPH

$$
Forecaster Latto

[aspen]

Douglas’ EWRC looks to be almost done. The secondary eyewall appears to have fully taken over as of a 13:50z microwave pass.

[Kingarabian]

Hurricane Douglas Discussion Number 17
NWS Central Pacific Hurricane Center Honolulu HI EP082020
500 AM HST Fri Jul 24 2020

Douglas remains a powerful hurricane early this morning, although
the satellite presentation has degraded quite a bit since last
evening, with eye of the tropical cyclone now nearly completely
cloud filled. The latest current intensity estimates from the
satellite agencies came in with 5.5 (102 knots) from PHFO and SAB,
5.0 (90 knots) from JTWC, while ADT came in at 5.9 (112 knots).
Taking a blend of the estimates above and accounting for recent
satellite trends, the intensity with this advisory will be lowered
to 105 knots. Douglas continues to move rapidly to the
west-northwest, with an initial motion set at 295/16 knots.

Hurricane Douglas recently moved over slightly cooler sea surface
temperatures (SSTs) of around 78F, and this seems to have been
enough to lead to the weakening seen in satellite imagery. Despite
relatively low vertical wind shear values forecast to affect the
tropical cyclone during the next couple days, SSTs will remain
unfavorable for intensification. The official intensity forecast
calls for steady weakening during the next couple days as Douglas
nears Hawaii, with the cyclone expected to be a category 1
hurricane or strong tropical storm approaching the eastern end of
the state late Saturday night or Sunday. Continued weakening is then
forecast as Douglas tracks westward over or near the other
main Hawaiian islands and west of the state early next week.
Depending on the amount of interaction with the high terrain of the
Big Island and Maui, the tropical cyclone could weaken faster than
indicated in the official forecast, which follows a blend of the
corrected consensus and statistical model guidance.

Douglas is forecast to move rapidly off to the west-northwest
during the next couple days toward a weakness in the sub-tropical
ridge north of the Hawaiian islands. The subtropical ridge is
forecast to strengthen north of the state over the weekend, and this
should steer the tropical cyclone westward over or very near the
Hawaiian Islands Sunday through Monday, before exiting to the west
of the state. The official forecast continues to hug the southern
end of the guidance envelope out of respect for the ECMWF, but if
model trends continue, this track may need to be adjusted further
northward in future advisory packages.

Based on the latest intensity and track forecasts, Hurricane or
Tropical Storm watches will likely be required for portions of the
eastern end of the state (Big Island and the Maui County Islands)
later today.


Key Messages:

1. Douglas is expected to move near or over portions of the main
Hawaiian Islands Sunday through Monday, and there is an increasing
chance that strong winds, dangerous surf, and heavy rainfall could
affect portions of the state beginning late Saturday night or
Sunday. Interests on the Hawaiian Islands should continue to monitor
the progress of Douglas and the official forecasts as they evolve
during the next few days.


FORECAST POSITIONS AND MAX WINDS

INIT 24/1500Z 16.4N 141.9W 105 KT 120 MPH
12H 25/0000Z 17.4N 144.3W 95 KT 110 MPH
24H 25/1200Z 18.6N 147.5W 85 KT 100 MPH
36H 26/0000Z 19.6N 150.4W 75 KT 85 MPH
48H 26/1200Z 20.5N 153.4W 70 KT 80 MPH
60H 27/0000Z 21.1N 156.1W 65 KT 75 MPH
72H 27/1200Z 21.7N 158.8W 55 KT 65 MPH
96H 28/1200Z 22.5N 165.0W 50 KT 60 MPH
120H 29/1200Z 23.5N 171.5W 45 KT 50 MPH

$$
Forecaster Jelsema

[aspen]

EWRC has gone very smoothly. The eye should be fully opened up again by the end of the day.

[HurricaneEnzo]

EWRC has gone very smoothly. The eye should be fully opened up again by the end of the day.
https://rammb-data.cira.colostate.edu/tc_realtime/products/storms/2020ep08/1kmsrvis/2020ep08_1kmsrvis_202007241751.gif

Looks like 80-90kts currently.

[Yellow Evan]

TXPN23 KNES 241755
TCSCNP

A. 08E (DOUGLAS)

B. 24/1730Z

C. 16.2N

D. 142.6W

E. ONE/GOES-W

F. T4.5/5.5

G. IR/EIR/VIS/SSMIS

H. REMARKS...AN OW EYE, SURROUNDED BY LG AND EMBEDDED IN MG MAKES THE
EYE-NO AND DT 4.5. THE MET IS A 5.0 AND THE PT IS A 4.5. THE FT IS BASED
ON DT.

I. ADDL POSITIONS

24/1414Z 16.2N 141.8W SSMIS


...MLEVINE

[Yellow Evan]

TPPZ01 PGTW 241758

A. HURRICANE 08E (DOUGLAS)

B. 24/1720Z

C. 16.75N

D. 142.39W

E. FIVE/GOES17

F. T4.5/4.5 STT: S0.0/03HRS

G. IR/EIR/VIS/MSI

H. REMARKS: 44A/PBO LARGE CDO/ANMTN. LLCC EMBEDDED IN LG YIELDS
A DT OF 4.5. MET/PT AGREE. DBO DT.

I. ADDITIONAL POSITIONS: NONE


ELIAS

[Kingarabian]

Anyone have verification plots that show Douglas's actual track vs forecast tracks?

[TheAustinMan]

Anyone have verification plots that show Douglas's actual track vs forecast tracks?

Here's the trend in the official track. This and other model deviation plots are available on Brian Tang's website. The trend has been slightly north but still points towards Hawaii.

75 KB.

[Kingarabian]

Anyone have verification plots that show Douglas's actual track vs forecast tracks?

Here's the trend in the official track. This and other model deviation plots are available on Brian Tang's website. The trend has been slightly north but still points towards Hawaii.

75 KB.
https://i.imgur.com/p1hG1QD.png

Thanks!!! Really appreciate it.

[Kingarabian]

UW - CIMSS
ADVANCED DVORAK TECHNIQUE
ADT-Version 9.0
Tropical Cyclone Intensity Algorithm

----- Current Analysis -----
Date : 24 JUL 2020 Time : 192032 UTC
Lat : 16:55:48 N Lon : 143:01:47 W


CI# /Pressure/ Vmax
5.1 / 968.3mb/ 92.4kt


Final T# Adj T# Raw T#
5.1 5.2 5.2

Estimated radius of max. wind based on IR : 21 km

Center Temp : +3.8C Cloud Region Temp : -55.5C

Scene Type : EYE

[Kingarabian]

Slowly losing its banding features. Think the annular transition is progressing.

[Kingarabian]

...MAJOR HURRICANE DOUGLAS CONTINUES TO TRACK TOWARD THE HAWAIIAN
ISLANDS...
...HURRICANE WATCH ISSUED FOR THE BIG ISLAND AND MAUI COUNTY...


SUMMARY OF 1100 AM HST...2100 UTC...INFORMATION
-----------------------------------------------
LOCATION...17.0N 143.5W
ABOUT 785 MI...1260 KM ESE OF HILO HAWAII
ABOUT 985 MI...1585 KM ESE OF HONOLULU HAWAII
MAXIMUM SUSTAINED WINDS...115 MPH...185 KM/H
PRESENT MOVEMENT...WNW OR 295 DEGREES AT 18 MPH...30 KM/H
MINIMUM CENTRAL PRESSURE...967 MB...28.56 INCHES

Hurricane Douglas Discussion Number 18
NWS Central Pacific Hurricane Center Honolulu HI EP082020
1100 AM HST Fri Jul 24 2020

After a period of rapid intensification yesterday, Douglas'
satellite appearance has degraded somewhat over the past 12 hours
or so. However, a fairly large but ragged and cloud-filled eye is
still noted in conventional satellite images. Subjective Dvorak
current intensity estimates were 5.5/105 kt from SAB and HFO, 5.1/93
kt from ADT, while SATCON estimated was near 100 kt. A blend of
these led to an initial intensity estimate of 100 kt for this
advisory.

The initial motion for this advisory is a steady 295/16 kt, as
Douglas continues to be steered by a robust mid-level ridge
centered to the northeast. As Douglas draws closer to the main
Hawaiian Islands, it will be reaching the western periphery of the
ridge, and model guidance indicates that this will allow the cyclone
to gain some latitude over the next 2 days, with some reduction in
forward speed. Thereafter, the mid-level ridge is forecast to
subtly build to the north of Douglas, potentially inducing a turn
toward the west, with some increase in forward speed. The updated
track forecast is nearly identical to the previous, lies along the
southern side of the guidance, and is very close to ECMWF guidance
that has been performing well thus far with Douglas. On the
forecast track, Douglas will move dangerously close to the Hawaiian
Islands. A Hurricane Watch has been issued for Maui County and
the Big Island, and may need to be expanded to additional areas
later today or tonight.

The intensity forecast continues to anticipate a slow but steady
weakening of the cyclone as it traverses cooler waters, and later
encounters increased vertical wind shear as waters warm somewhat
near the Hawaiian Islands. Little overall change to the ongoing
forecast was made, and the updated forecast closely follows the
GFS- and ECMWF-based SHIPS guidance, and is close to the intensity
consensus IVCN.

Key Messages

1. Douglas will continue to quickly approach the main Hawaiian
Islands, passing dangerously close to, or over, the islands on
Sunday. Dangerous, life-threatening surf will arrive ahead of the
hurricane on Saturday. Heavy rain and increasing winds are possible
on the Big Island starting Saturday night, and could quickly spread
up the chain Sunday.

2. It is important not to focus on the exact forecast track. Due
to Douglas' angle of approach to Hawaii, any small changes in the
track could lead to significant differences in where the worst
weather will occur.

3. Wind gusts near mountains and higher terrain can be
significantly enhanced as they blow downslope.


FORECAST POSITIONS AND MAX WINDS

INIT 24/2100Z 17.0N 143.5W 100 KT 115 MPH
12H 25/0600Z 17.9N 145.9W 90 KT 105 MPH
24H 25/1800Z 19.1N 149.0W 80 KT 90 MPH
36H 26/0600Z 20.0N 151.9W 70 KT 80 MPH
48H 26/1800Z 20.8N 154.7W 65 KT 75 MPH
60H 27/0600Z 21.3N 157.5W 60 KT 70 MPH
72H 27/1800Z 21.8N 160.4W 55 KT 65 MPH
96H 28/1800Z 23.0N 166.7W 50 KT 60 MPH
120H 29/1800Z 24.2N 172.8W 45 KT 50 MPH

$$
Forecaster Birchard

[Astromanía]

Will it reach the date line?

[Kingarabian]

Will it reach the date line?

Maybe. If it does, it will give the WPAC that well sought after TS.

[Ntxw]

[Yellow Evan]

Will it reach the date line?

The globals are forecasting a spike in shear around 155W which won't relent so probably not.

[Kingarabian]

UW - CIMSS
ADVANCED DVORAK TECHNIQUE
ADT-Version 9.0
Tropical Cyclone Intensity Algorithm

----- Current Analysis -----
Date : 24 JUL 2020 Time : 215031 UTC
Lat : 17:16:48 N Lon : 143:45:00 W


CI# /Pressure/ Vmax
5.4 / 962.4mb/ 99.6kt


Final T# Adj T# Raw T#
5.4 5.5 5.5

Estimated radius of max. wind based on IR : 25 km

Center Temp : +9.5C Cloud Region Temp : -57.4C

Scene Type : EYE