625am OBS Tuesday 4/20/21
Calm, clear conditions early but possible showers and thunderstorms this afternoon. Calm-Light ENE trades early; sea breezy later. No marine warnings.
Small fading NNW. Tiny inconsistent SW & filling E swell. Call 596-SURF: 7a, noon & 5p (recap-forecast).

North Shore:
Dropping 9 sec NNW, Surf's clean and glassy with calm-light winds early. Sunset to Rocky Pt 1-2 occ +; Pipeline/Backdoor 0-1.5 maybe a plus'; Chuns 0-1.5'; Laniakea 1-2 maybe a plus'; Haleiwa 1 occ 2'; Clear skies.
West:
Dropping 9 sec NNW + Dropping Slow 15 sec SW. Makaha is a mixed plate 0-1 occ 2' breaking inside the reef and glassy with super-lite offshores switching to sea breezes late AM. Clear skies.
Town:
Dropping 15 sec SW. Surf's clean and glassy due to calm-lite offshores. Waikiki reefs are 0-1 very occ. 2'. Ala Moana, Kaisers-Rockpiles & Kewalos are 0-1 occ 2' sets every once in a while. Clear skies.
Diamond Head:
Dropping 15 sec SW. Surfs small but glassy and fun at 1-2 occ + (Knee-Waist occ Chest). Mostly clear.
Sandy's:
Dropping 15 sec SW. Surf's tiny but excellent conditions w/ calm-lite winds. Full Pt-Half Pt is 1-2'; Shorebreak's breaking right on the sand at 1 occ 2', focusing towards Cobbles/Middles with plenty rocks. Clear skies.
East Makapu'u:
Dropping 9 sec N wrap + Rising 7 sec E swell. Surf's clean with calm-light winds, 1 occ 2' breaking right on the shore with a couple of little barrels toward Keiki's. Mostly clear.Winds
5-10mph East Trade
Sea breezes toward lunch
5-10mph Variables
Afternoon sea breezes
5-10mph ENE Trade
5-15mph NE Trade
5-15mph NE Trade
North
Primary

Haw: 1-2 occ +
Face: 1-3 occ +
Secondary
Rising Nightime 15s NNWHaw: 1-2
Face: 1-3
Smooth early-mushy later
Primary
Up & Rising 13s NNWHaw: 2-3
Face: 3-5
Secondary
None NONEHaw: 0
Face: 0
Smooth early-mushy midday
4' afternoon
Primary
Up & holding 11s NNWHaw: 3-5
Face: 5-9
Secondary
None NONEHaw: 0
Face: 0
Good early , fair later
Primary
Dropping Slow 10s NNWHaw: 2-3
Face: 3-5
Secondary
None NONEHaw: 0
Face: 0
Good offshores
Primary

Haw: 1-2+
Face: 1-3+
Secondary
Rising Slow 16s WHaw: 0-1
Face: 0-1.5
Good offshores
West
Primary
Dropping Slow 15s SWHaw: 0-1.5
Face: 0-2
Secondary

Haw: 1 occ 2
Face: 1-2 occ 3
Smooth early-mushy later
Primary
Up & Rising 13s NNWHaw: 1-2+
Face: 1-3+
Secondary

Haw: 0-1.5
Face: 0-2
Smooth early-mushy midday
Primary
Up & holding 11s NNWHaw: 2-3+
Face: 3-5+
Secondary
Up & Rising 18s SWHaw: 1 occ 2
Face: 1-2 occ 3
Good early , fair later
Primary
Dropping Slow 10s NNWHaw: 1-2+
Face: 1-3+
Secondary
Up & holding 16s SWHaw: 1-2
Face: 1-3
Good offshores
Primary

Haw: 0-2
Face: 0-3
Secondary

Haw: 1-2
Face: 1-3
Good offshores
South
Primary
Dropping Slow 15s SWHaw: 1 occ 2
Face: 1-2 occ 3
Secondary
None NONEHaw: 0
Face: 0
Smooth early-mushy later
Primary

Haw: 1 occ 2
Face: 1-2 occ 3
Secondary

Haw: 0-1.5
Face: 0-2
Smooth early-mushy later
Primary
Up & Rising 18s SWHaw: 1-2
Face: 1-3
Secondary

Haw: 1-1.5
Face: 1-2
Smooth early-mushy later
Primary
Up & holding 16s SWHaw: 1-2 occ +
Face: 1-3 occ +
Secondary
None NONEHaw: 0
Face: 0
Fair to good
Primary

Haw: 1-2 occ +
Face: 1-3 occ +
Secondary
None NONEHaw: 0
Face: 0
Fair to good
east
Primary
Up & Rising 7s EHaw: 1 occ 2
Face: 1-2 occ 3
Secondary

Haw: 0-1.5
Face: 0-2
Diving , Paddling
N wrap
Primary
Up & Rising 9s EHaw: 1-2
Face: 1-3
Secondary

Haw: 1-2
Face: 1-3
Smooth early-mushy later
N wrap, 3' evening
Primary
Up & holding 9s EHaw: 1-2
Face: 1-3
Secondary

Haw: 1-2 occ +
Face: 1-3 occ +
Fair
N wrap
Primary

Haw: 1-2
Face: 1-3
Secondary

Haw: 1-2
Face: 1-3
slightly bumpy
N wrap, 2.5' later
Primary

Haw: 1-2
Face: 1-3
Secondary

Haw: 1-1.5
Face: 1-2
slightly bumpy
N wrap

Current Swells:
Tuesday 04/20Primary: Dropping 9s NNW surf @1-2 occ +
Secondary: Dropping Slow 15s SW surf @1 occ 2
Third: Up & Rising 7s E surf @1 occ 2

Marine Warnings:
Tuesday 04/20None

Sailing Report:
Tuesday 04/20Poor to fair due to light ENE trades

Diving Report:
Tuesday 04/20Fair for most North shore zones due to tiny lingering NNW swell; good for most top Westside spots; good for most deeper zones along South shores due to small inconsistent swell; good for most top spots inside and outside reefs along Windward
Oahu
Maui
Kauai
Big Island
Weather
Surf Advisory and Warning CriteriaLocation/shoreline Advisory Warning
North-Facing Shores- 15 Feet faces (8' Local) 25 Feet faces (15' local)
West-Facing Shores - 12 Feet (7' local) 20 Feet (12' local)
West-Facing- Big Is.- 8 Feet (4'+ local) 12 Feet (7' local)
South-Facing Shores- 8 Feet (4'+ local) 15 Feet (8' local)
East-Facing Shores- 8 Feet (4'+ local) 15 Feet (8' local)
Big Picture
INACTIVE.Get the latest on the tropics at www.hurricanes.gov
The Central Pacific Hurricane Center outlook for the 2017 Central Pacific Hurricane Season calls for 5 to 8 tropical cyclones to either develop or cross into the Central Pacific with a 40% chance for an above-normal season, a 40% chance for a normal season, and a 20% chance for a below-normal season. An average season has 4 to 5 tropical cyclones, which include tropical depressions, tropical storms, and hurricanes.
A tropical depression forms when a low-pressure area is accompanied by thunderstorms that produce a circular wind flow with maximum sustained winds below 39 mph. An upgrade to a tropical storm occurs when cyclonic circulation becomes more organized and maximum sustained winds gust between 39 mph and 73 mph. A tropical storm is then upgraded into Category 1 hurricane status as maximum sustained winds increase to between 74 mph and 95 mph. (The highest classification in the scale, Category 5, is reserved for storms with winds exceeding 156 mph).
Tropical cyclones go by many names around the world, and the terminology can get confusing. Once a tropical cyclone strengthens to the point where it has gale-force winds—39 mph or greater—it becomes a tropical storm. A storm that reaches tropical storm strength usually gets its own name to help us quickly identify it in forecasts and warnings. Once a tropical storm begins producing sustained winds of around 75 mph, we call the storm a typhoon in the western Pacific near Asia and a hurricane in the oceans on either side of North America. A “typhoon” and a “hurricane” are the same kind of storm, they just go by different names…it’s only a matter of geography.
NWS criteria for High Surf Advisories & Warnings.
In coordination with civil defense agencies & water safety organizations in Hawai`i, the NWS uses the criteria below for the issuance of High Surf Advisories & Warnings in coordination with civil defense agencies & water safety organizations in Hawai`i.
All surf height observations & forecasts are for the full face surf height, from the trough to the crest of the wave.
Advisory and Warning Criteria Location
Warning North-Facing Shores 15 Feet 25 Feet
West-Facing Shores - Remaining Islands 12 Feet 20 Feet
West-Facing Shores - Big Island 8 Feet 12 Feet
South-Facing Shores 8 Feet 15 Feet
East-Facing Shores 8 Feet 15 Feet
'Travel Time' Buoy 51101 to Waimea Buoy. Distance: 269 nautical miles (~310 miles). Angle: 307 deg
Wave Wave Wave Depth Wave Direction (deg)----------
Period Length Speed Shallow 295, 305, 315, 325, 335, 345, 355
(s) (ft) (nm/h) (ft) Travel Time (hours)----------
10sec. 512. 15. 256. 17.3, 17.7, 17.6, 16.9, 15.7, 14.0, 11.9
12sec. 737. 18. 369. 14.5, 14.8, 14.6, 14.0, 13.0, 11.6, 9.9
14sec. 1003. 21. 502. 12.4, 12.7, 12.5, 12.0, 11.2, 10.0, 8.5
16sec. 1310. 24. 655. 10.8, ,1 1.1, 11.0, 10.5, 9.8, 8.7, 7.4
18sec. 1658. 27. 829. 9.6, 9.8, 9.8, 9.4, 8.7, 7.8, 6.6
20sec. 2047. 30. 1024. 8.7 8.9 8.8 8.4 7.8 7.0 5.9
22sec. 2477. 33. 1239. 7.9 8.1 8.0 7.7 7.1 6.3 5.4
24sec. 2948. 36. 1474. 7.2 7.4 7.3 7.0 6.5 5.8 4.9
Tropical Storms - wind 39-73 mph (34-63 kt)
Category 1 - winds 74-95 mph (64-82 kt)
Category 2 -winds 96-110 mph (83-95 kt)
Category 3 -winds 111-130 mph (96-113 kt)
Category 4 - winds 131-155 mph (114-135 kt)
Category 5 -winds 156 mph and up (135+ kt)
Please visit the Central Pacific Hurricane Center website at www.weather.gov/cphc for the most recent bulletins.
ENSO is a single climate phenomenon, it has three states or phases. The two opposite phases, “El Niño” and “La Niña,” require certain changes in both the ocean and the atmosphere because ENSO is a coupled climate phenomenon. “Neutral” is in the middle of the continuum. The MJO (Madden-Julian Oscillation) is an eastward moving disturbance of clouds, rainfall, winds, and pressure that traverses the planet in the tropics and returns to its initial starting point in 30 to 60 days, on average, unlike ENSO which is stationary. In a nutshell, more active means more surf.
Kelvin wave (A Kelvin wave is a wave in the ocean or atmosphere that balances the Earth's Coriolis force against a topographic boundary such as a coastline, or a waveguide such as the equator. A feature of a Kelvin wave is that it is non-dispersive, i.e., the phase speed of the wave crests is equal to the group speed of the wave energy for all frequencies. This means that it retains its shape as it moves in the alongshore direction over time.)
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