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2020 tropical storm / hurricane thread
#40
No wind or rain here. According to Windy the gusts should start in a few hours but will be nothing significant. They added Kauai to the hurricane warning. Basically the entire state is under a hurricane warning except for the BI where it has been cancelled.

WTPA32 PHFO 261439
TCPCP2

BULLETIN
Hurricane Douglas Advisory Number 25
NWS Central Pacific Hurricane Center Honolulu HI EP082020
500 AM HST Sun Jul 26 2020

...DANGEROUS HURRICANE DOUGLAS CLOSING IN ON THE HAWAIIAN ISLANDS...
...HURRICANE WARNING ISSUED FOR MAUI COUNTY...


SUMMARY OF 500 AM HST...1500 UTC...INFORMATION
----------------------------------------------
LOCATION...20.7N 154.3W
ABOUT 145 MI...230 KM E OF KAHULUI HAWAII
ABOUT 235 MI...380 KM E OF HONOLULU HAWAII
MAXIMUM SUSTAINED WINDS...90 MPH...150 KM/H
PRESENT MOVEMENT...WNW OR 285 DEGREES AT 16 MPH...26 KM/H
MINIMUM CENTRAL PRESSURE...983 MB...29.03 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY...

The Hurricane Watch for Maui County, including the islands of Maui,
Lanai, Molokai and Kahoolawe has been upgraded to a Hurricane
Warning.

The Hurricane Watch has been canceled for Hawaii County.

A Tropical Storm Watch has been issued for portions of the
Papahanaumokuakea Marine National Monument from French Frigate
Shoals to Maro Reef.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT...

A Hurricane Warning is in effect for...
* Maui County, including the islands of Maui, Lanai, Molokai and
Kahoolawe
* Oahu
* Kauai County, including the islands of Kauai and Niihau

A Tropical Storm Warning is in effect for...
* Hawaii County

A Tropical Storm Watch is in effect for...
* Portions of the Papahanaumokuakea Marine National Monument from
Nihoa to French Frigate Shoals to Maro Reef.

A Hurricane Warning means that hurricane conditions are expected
somewhere within the warning area, in this case within the next
24 hours.

A Tropical Storm Warning means that tropical storm conditions are
expected somewhere within the warning area, in this case within the
next 12 hours.

A Tropical Storm Watch means that tropical storm conditions are
possible within the watch area, in this case within the next 36 to
48 hours.

Interests elsewhere in the Papahanaumokuakea Marine National
Monument should monitor the progress of this system.

For storm information specific to your area, please monitor
products issued by the National Weather Service office in
Honolulu Hawaii.


DISCUSSION AND OUTLOOK
----------------------
At 500 AM HST (1500 UTC), the center of Hurricane Douglas was
located near latitude 20.7 North, longitude 154.3 West. Douglas is
moving toward the west-northwest near 16 mph (26 km/h) and this
motion is expected to continue over the next couple of days. On the
forecast track, Douglas will pass near, or over, the islands from
Maui to Kauai today and tonight.

Maximum sustained winds are near 90 mph (150 km/h) with higher
gusts. Gradual weakening is forecast during the next 48 hours, but
Douglas is expected to remain a hurricane as it moves through the
islands.

Hurricane-force winds extend outward up to 30 miles (45 km) from the
center and tropical-storm-force winds extend outward up to 105 miles
(165 km).

The estimated minimum central pressure is 983 mb (29.03 inches).


HAZARDS AFFECTING LAND
----------------------
WIND: Hurricane conditions are expected in portions of Maui County
today, on Oahu by this afternoon, and on Kauai and Niihau tonight.
Tropical Storm conditions are imminent across the Big Island.
Due to the steep terrain of the islands, hurricane-force wind
gusts are possible even within the tropical storm warning area.

SURF: Large swells generated by Douglas will affect the Hawaiian
Islands into Monday, producing life-threatening and potentially
destructive surf along exposed shores.

STORM SURGE: The combination of higher than predicted water
levels, dangerous storm surge, and large breaking waves will raise
water levels by as much as 3 feet above normal tides near the center
of Douglas.

RAINFALL: Heavy rainfall associated with Douglas is expected to
affect portions of the main Hawaiian Islands from early this
morning into Monday. Total rain accumulations of 5 to 10 inches are
possible from Maui County westward to Kauai County, with the
greatest amounts up to 15 inches in elevated terrain. This rain may
result in life-threatening flash flooding and land slides, as well
as rapid water level rises on small streams. Douglas could produce
an additional 2 to 4 inches of rainfall over the northern half of
the Big Island.

Key messages for Douglas can be found in the Tropical Cyclone
Discussion under AWIPS header HFOTCDCP2 and WMO header WTPA32 PHFO.


NEXT ADVISORY
-------------
Next intermediate advisory at 800 AM HST.
Next complete advisory at 1100 AM HST.

$$
Forecaster Birchard

000
WTPA42 PHFO 261451
TCDCP2

Hurricane Douglas Discussion Number 25
NWS Central Pacific Hurricane Center Honolulu HI EP082020
500 AM HST Sun Jul 26 2020

Hurricane Hunters from the Air Force 53rd Weather Reconnaissance
Squadron spent most of the night with Douglas, making 5 passes
through the center. The final pass contained some of the strongest
winds of the entire mission, with flight-level winds near 100 kt,
SFMR winds up to 79 kt, and a relatively steady pressure reading
near 983 mb. The initial intensity was maintained at 80 kt based on
these valuable data points. Also of extreme value is the fact that
the low-level center is south of the apparent center seen in
conventional satellite imagery, and closer to the islands than
might be otherwise expected. Although island-based radars are also
detecting Douglas' circulation, they are sampling the upper
portions of the cyclone that are sheared northward due to southerly
vertical wind shear.

Despite the vertical wind shear, Douglas has been slow to weaken,
and this trend will continue today as Douglas passes near, or
potentially over, the islands. Steadily increasing SSTs along the
forecast track are expected to limit the rate of weakening, while
the noted vertical wind shear may be confined to the upper-levels.
While Douglas is on the western edge of a ridge aloft, leading to
high-level southerly shear, a mid-level ridge is expected to build
westward to the north of Douglas through Monday, likely allowing
the low- to mid-level core of the cyclone to remain intact. The
updated intensity forecast once again closely follows the consensus
IVCN, and maintains Douglas as a hurricane until it passes west of
the islands. Steady weakening will occur thereafter due to
persistent southwesterly shear.

The mid-level ridge will continue to drive Douglas toward the west-
northwest, with the current motion vector estimated to be 285/14
kt. The forecast track takes the center of Douglas dangerously close
to the islands from Maui to Kauai through tonight, where a Hurricane
Warning is in effect. The updated forecast track is very close to
the previous forecast and the high-performing ECMWF guidance, and
anticipates some acceleration toward the west in the later periods
as the increasingly shallow system gets steered by the low-level
trade wind flow.

Key Messages

1. Douglas will pass dangerously close to, or over, the islands
today, bringing a triple threat of hazards, including but not
limited to damaging winds, flooding rainfall, and dangerously high
surf, especially along east and north facing shores.

2. It is remains important that you do not focus on the exact
forecast track of Douglas. Due to Douglas' angle of approach to the
islands, any wobble in the track could lead to significant
differences in where the worst weather occurs. Even if the center
remains offshore, severe impacts could still be realized over the
islands, as they extend well away from the center.

3. Terrain effects can cause strong localized acceleration of the
wind through gaps and where winds blow downslope. These acceleration
areas will shift with time as Douglas passes near the islands.
Hurricane force wind gusts are possible even within the tropical
storm warning area. Winds will also be stronger at the upper floors
of high rise buildings.


FORECAST POSITIONS AND MAX WINDS

INIT 26/1500Z 20.7N 154.3W 80 KT 90 MPH
12H 27/0000Z 21.4N 156.6W 75 KT 85 MPH...NEAR MAUI COUNTY
24H 27/1200Z 22.3N 159.5W 70 KT 80 MPH...NEAR KAUAI
36H 28/0000Z 22.8N 162.7W 60 KT 70 MPH
48H 28/1200Z 23.3N 166.1W 55 KT 65 MPH
60H 29/0000Z 23.7N 169.5W 50 KT 60 MPH
72H 29/1200Z 24.0N 173.0W 45 KT 50 MPH
96H 30/1200Z 24.5N 179.5E 35 KT 40 MPH
120H 31/1200Z 25.5N 172.0E 30 KT 35 MPH

$$
Forecaster Birchard
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RE: 2020 tropical storm / hurricane thread - by terracore - 07-26-2020, 05:41 PM

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