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Weather

Surf Advisory and Warning Criteria
Location/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

BIG PICTURE Update Monday 5/15/17
NPAC:

#1 Recent: Surf’s was unreal overall early May. Then it's been back to 'normal' with mostly NE windswell this past weekend & today. Still, we can expect a springlike NW this week.

#2 Next: This weekend a weak slow tracking Low moved E to ESE from the west Aleutians just reaching the dateline 1200 miles NW as winds weaken over Thursday-Monday. Buoys should show it after dark Wednesday the 17th & by Thursday we should have some 2-3’ surf (head high) at 11sec. It’ll be almost 3’ on Friday, disappearing from there.

#4, Last: We see some complex semi occluding low pressure to our NW on our side of the dateline Friday the 19th. We could see some short 10 sec period surf from the NW reach 2’ maybe 3’ sometime later Sunday into Monday the 21-22nd.

SPAC

The Jet has recently been sorta quiet and weak. Yet, overall it has been fattened up and empowered off & on as we ‘Fall toward Winter’ down under. It’s been a decent run of SSW to SSE swells. We’ve already had a handful this spring and there’s at least 6 more coming in May. This Thursday 5/18 the Jet improves with a NE flow to the SE and up the coast of NZL in a broad large arc up over a high far east of NZL. Plenty energy overall. Right now it’s HEADS UP for thee biggest SSW we’ve seen in awhile(read below). Many thanks to this Jet pattern improvement later this week.

#1 Recent: Plenty small but fun kine surf from the S-SSW has been regularly sweeping into the southern exposures all month. The recent one was 14sec and solid 2-3’ sets at best breaks with brisk side-off ENE trades and scattered clouds. Plenty crowds this last wkend. The creator was a low south of Tahiti on Cinco de Mayo. The South should peaked thru Sunday at 3’ solid.

#2 Next: There’s another broader S-SSW than the last one (South) at 15 secs so a little more power but a portion of this is ‘sideband’ swell limiting ‘the hit’ (=plenty fetch pointing to Americas). It’s filling by early Tuesday up to 3’ or head high and this one will veer South to SSE and hold thru Wednesday. Trades will have backed off for cleaner surf.

#3 Next: A tropical Low named Donna morphed into a cold core low (extra tropical) off the East coast of North NZL last Saturday the 13th only 3200 miles off. Due to the fact it’s nearly 1000 miles nearer than may SSW producers, we could and should see some 3+’ SSW surf at 16 sec filling Friday the 19th peaking through Saturday 20th.

#4 NEXT: Slight downgrade from Saturday 5/13. But confidence is building that a BIG one is possible. By Friday the 19th there’s a big Low just off the SE coast of NZL. It has up to 38'seas. The NNE track is good but it does start close to the coast into Saturday w/a semi captured fetch where it weakens quickly with up to 30' seas. WW3 is on Monday claims 1' 20 sec forerunners Thursday morning (intial trend was going from 2-3' at 20s). Deep water swell will reach 2’ 18sec late Thursday building all nite. Friday morning 5/26 should get 3+'swell @ 18s creating occas 6' sets at top spots and increase in size & regularity that afternoon. It'll start off slow with lulls due to long travel distance. The super long period will focus, refract, shoal these fat & fast open ocean swells into way above advsry level surf (just 8'faces) for top reefs Friday-Sunday... at least(Warnings are 8’ Hawaiian or 15’ faces. Models hinted this last Saturday & it will near it at this point of the chart forecasts). The surf will be crankin' 5-7’ (12'faces) at dawn Saturday the 27th with buoys at 4+' @ 16. The episode will very slowing fade from there with some 4-6' Sunday, 3-5 Monday. (Again, as we always NOTE: Monday is still model fantasy; we want you to have a ‘heads up’. We'll know better & better this Wednesday/Thursday and especially Fri/Saturday (17-20th).

#5 NEXT: Sunday's models show a fast backup storm in the same area SE of NZL by Sunday May 21st. It's weaker but tracking NNE with a partially captured fetch & still substantial seas up to 30'. The Low weakens Monday with 28' seas. So, the end result for Hawaii suggests 3+' deep water at 15sec Monday nite the 29th with Tuesday dawn showing surf solid 3-5'. This one-two punch will keep us way overhead 6 days straight.

#6 LAST: Models fantasize yet another Low further ESE of NZL by Tuesday 5/23 for a possible 3-5' SSW on the last day of May. We'll go with 50/50 for now.

Trade swells

Trades have been back for a while & quite strong & gusty. Thus, the uptick in advsry surf of solid 4+' Saturday-Monday. Of course, it’s more chopped & chunky. That strong 1035mb high is staying ‘round thru Monday but it's slowly easing as it drifts east. The long upstream fetch allowed the wind-swell (trades) to bump up to 9-10sec, enough for an extra 1-2’ higher surf from greater shoaling, refraction & diffraction (read below). We'll get back to our typical 7-8sec trade swell of 2’ or 2.5’ or waist to chest this Thursday onward.

Shoaling is the effect by which surface waves entering shallower water change in wave height (or grow) due to speed change (or slow down). Wave length is reduced when going from deeper to shallower. The ‘energy flux’ must remain constant (nature’s liquid law) so the reduction in wave group (transport) speed is compensated by an increase in wave height (and thus wave energy density). Yeah, I know…waves are complex AND amazing.
Refraction is the change in direction of waves that occurs when waves travel from one medium to another or depth change. Refraction is always accompanied by a wavelength & speed change. Diffraction is the bending & spreading of waves around obstacles (‘reefs’ and openings).

The Tropics
So far nothing on the forecast for Hawaii for the next week. Last week Wednesday the 10th ‘Adrian’ weakened but not after becoming the earliest tropical storm on record in the East Pac! The official start of East Pac Hurricane season in May 15th.





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 Advisory Warning
North-Facing Shores 15 Feet 25 Feet
West-Facing Shores - Big Island 8 Feet 12 Feet
West-Facing Shores - Remaining Islands 12 Feet 20 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



Surf Advisory and Warning Criteria

Location/shoreline Advisory Warning
North-Facing Shores- 15 Foot faces (8' Local) 25' Foot faces (15' local)
West-Facing Shores - 12 Foot (7' local) 20 Foot (12' local)
West-Facing- Big Is. - 8 Foot (4'+ local) 12 Foot (7' local)
East-Facing Shores- 8 Foot (4'+ local) 15 Foot (8’ local)

Tropical Storm - winds 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.