SURF N SEA BLOW OUT 2020. 728 11.30-

Big Picture

Tuesday, December 1st – Wednesday, December 9th

Local Weather Outlook –

A mix of light easterly trades and variables with afternoon sea breezes through Thursday, northerlies on Friday, trades on Saturday, and back to the mix on Sunday into next week.

Due to the recent northeasterly winds, a drier airmass has set in. The chill in the air will persist through Thursday with dew point temperatures in the low 60’s. On Friday, an inverted trough embedded within the easterly flow will bring the dew point back up to the upper 60’s.

A surface trough to the north has disrupted the trade wind pattern, leading to very light easterlies or offshore land breezes in the morning and onshore sea breezes in the afternoon. It will not be until Friday that weak ridging briefly returns with northerlies followed by easterlies on Saturday. On Sunday, another trough will approach the state and give way to a similar pattern of land and sea breezes.

The jet stream across the Pacific Ocean has trended southward and zonal. This has brought the storm track closer to Hawaii and, as a result, higher surf potential. Surf potential will remain high as the pattern sticks around for awhile.

Surf Outlook –

North and West Shores: Very large surf on Wednesday followed by more modest surf this weekend. Increasing potential for another very large NW-NNW swell next Sunday into Monday.

Over the past week, a series of troughs raced across the far northwestern Pacific Ocean, which gave way to subtle ups and downs in the small to moderate surf range. 2-4’ surf from the NW-NNW will continue this morning as a much larger NW swell begins to fill in later this afternoon.

Last Saturday, an area of low pressure spawned off the eastern coast of Honshu and rapidly deepened. It gained hurricane-force winds of 75-85 mph as it tracked east-northeast for roughly 1,000 nautical miles. The low then tracked straight east for another 1,000 miles with 60-70 mph winds for over 24 hours. It began to occlude on Monday as it crossed the dateline. Satellite altimetry measured seas of 40-45 feet but missed the highest seas. Recent passes over the region show that Wavewatch III is performing roughly on par with observations, giving higher confidence to its ouput.

Extra-long period forerunners of 23-24 seconds pinged the NW buoys early this morning. Trace amounts of energy in the 24-25 second band have also begun to show at Waimea as of this writing. Surf will rise rapidly to 4-6’ by early evening and 8-12’ before dark. The swell will peak mid-late morning on Wednesday at 15-25’+. The highest refracting outer reefs such as Peʻahi will see up to 30’. Surf will drop to more manageable levels of 10-15’ by Thursday morning and 8-12’ later in the day. 5-7’ surf with a 12 second period out of the NNW should become commonplace on Friday. The wind should make for some good to excellent conditions during the mornings but become less optimal for the afternoons of Wednesday and Thursday. Friday should be bumpy and mushy due to northerly winds.

A wide fetch of 30-40 mph with pockets of 45 mph winds is now forming off the Kurils and is modelled to come within 1,000 miles of Hawaii on Thursday. This will lead to consistent NW surf with 12-13 second periods rising late Friday to 4-6’ but may be imperceptible as it mixes in with the declining NNW swell. The swell period and height will increase a notch on Saturday to 6-8’ and then decrease to 4-6’ on Sunday.

Finally, another low is modelled to deepen east of Honshu and track to south of the one that will produce the very large NW surf. In comparison, this source looks to be more compact and have a shorter fetch as the rapid deepening occurs later in its track but have strong winds reach closer to Hawaii. This means a similarly sized, or perhaps a hair smaller, event with extra-long period forerunners arriving overnight Sunday and the potential for 15-25’ surf out of the NNW on Monday. If the model pans out, surf will drop to 8-12’ on Tuesday and 6-8’ on Wednesday. There is much to fine-tune for this event as it is quite a ways off.

South Shores: Seasonably small December surf continues…

Tiny surf continues from background sources in the South Pacific. Focal spots that can take wrap from the west will trend up on Wednesday as the large NW swell fills in. Otherwise, minimal surf will persist through the week and weekend.

On Tuesday, a deep low is modelled to aim 50-60 mph winds at the Tasman Sea and generate seas of 40  feet. With the low tracking unfavorably southward, long period SW swell from this source not to exceed 2’ will arrive next Wednesday.

East Shores: Minimal trade swell but northerly wrap potential.

As the wind pattern shifts to a calmer regime dominated by passing troughs to the north, the trade swell will continue to decline to 2’ today and below that on Wednesday. The large NW swell will begin to show near dusk on Tuesday. Surf should rise to 2-4’+ on Wednesday, especially for northerly focal points. As the NW swell begins dropping on Thursday, so should the wrap – 2-3’+. Morning conditions should be fairly good under light trades or weak land breezes.

Trades will briefly return on Friday and Saturday, but the small fetch and duration means 1-2’ of chop added to the mix. The north wrap will hold at 1-2’+ through the weekend. Surf should trend up on Monday as another very large NNW swell fills in.

The East Pac Tropics: None for the upcoming week.

The West Pac Tropics: None for the upcoming week.

Long-range views are seldom 20/20. Prep for some adjustments.


Surf Climatology HERE

NWS criteria for High Surf Advisories (first number) & Warnings (second number).

All surf height observations & forecasts are for full ‘face’ surf height, or ‘trough to the crest’ of the wave.

North-Facing Shores 15 Feet and 25 Feet

West-Facing Shores – Remaining Islands 12 Feet and 20 Feet

West-Facing Shores – Big Island 8 Feet and 12 Feet

South-Facing Shores -(Advisory) 8 Feet and (warning) 15 Feet

East-Facing Shores – 8 Feet and 15 Feet

Get the latest Central Pac Hawaii HERE

For the SNN Buoys ‘per shore’ displayed   HERE

Note: Spectral density graph in the SNN Buoy Page HERE can show ‘slivers’ of forerunners that initial text readings of new swells which often do not ‘show’ till later on written/text buoy updates. Also, note the vertical graph is not ‘wave height’ rather its a measure of wave energy in hertz (frequency or cycles/sec) for the whole ‘band’ (the distribution of power/period in the total wave energy field/spectrum).

Links: Get the latest on the Eastern North Pac GO HERE 

For more on the West Pac Typhoons GO HERE

Common Terms:  Split Jetstream

Blocking ridge

Short-wave tough

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