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Big Picture

SNN BIG PICTURE: Updated Sunday 10:10pm 1/16

Monday, January 17th – Tuesday, January 25th

Local Weather Outlook –

Light winds continue this week but trades likely return by the weekend…

The local wind pattern has been dominated by an extremely active storm track across the western Pacific. Aided by a powerful 250mph zonal jet stream over the subtropical latitudes, lower pressure associated with storm activity filled much of the middle latitudes to well East of the dateline. The equatorward extent of the jet stream enabled storms to track across the Pacific Ocean and reach to within close proximity of Hawaii.

As a result, the state has been under a pattern of light and variable winds for quite some time. For Monday and Tuesday, an area of high pressure over the eastern Pacific will try to nudge towards Hawaii. This will lead to very light ESE flow of less than 10mph with widespread light afternoon sea breezes. Towards midweek, a front will dissipate to the North but weaken the area of high pressure. Winds will remain ESE but increase to 5-15mph for Wednesday and early Thursday. By late Thursday, winds will weaken once again as another front approaches. Light and variable winds will return for Friday as the front washes out to the North. High pressure will follow in behind the front and turn the winds NE for the weekend. The winds will start light for Saturday but bump up to 10-15mph for Sunday and potentially stronger and even more towards NNE for early next week as a subtropical low comes to within close proximity of Hawaii from the East.

Surf Outlook –

North and West Shores: More large WNW swells, including another XL+, on the way…

Recent/Now: The aforementioned large scale pattern over the Pacific maximizes surf potential. This has been seen for over the course of more than one week now. The foot is down hard on the accelerator, and the gas tank shows no signs of losing steam. Last Wednesday, a compact low broadened from just West of the dateline and tracked ESE with winds of 50-60mph. A satellite pass indicated seas of 22’ reaching to within 1,100 nautical miles of Hawaii on Friday. The result was a rise in surf from the WNW-NW to 6-8’+ Hawaiian scale by late Saturday, peaking at 8-12’ for the first half of Sunday. Heights fell a pinch later on Sunday. The close proximity of the compact low ensures a steady to rapid fall in surf. Surf will be down to 2-4’+ by dawn on Monday and 2-3’ past lunch.

Next: The next source had two parts. Last Friday, a massive area of low pressure emerged from the Kuril Islands. On Saturday, a long, wide fetch of 35-45mph winds were directly aimed at the state. The broad system took a jog to the East, which brought the fetch closer. The second part involved a trough dropping equatorward on the eastern flank of the low on Sunday. Winds from this trough were of similar magnitude but reached closer to Hawaii. Part one of the source will arrive on Monday as 15-17 second middle period forerunners from the WNW. Surf should gradually build from 2-4’+ at dawn Tuesday to 4-6’ at dusk. Part two will arrive later on Tuesday, allowing for surf to continue building overnight. It should peak at 6-8’+ with top sets near 10’ possible on Wednesday. Surf will drop on Thursday from 6-8’+ in the morning to 5-7’ in the afternoon.

Next: This swell began to develop late Sunday as a weak trough sharpened off the coast of Honshu and accelerated eastward. It will reach the dateline early Tuesday with 30-40mph winds. Middle period forerunners should arrive predawn on Friday from the WNW. Surf from this source should hold at 5-8’ on Friday as the swell height increases but the period decreases.

Next (BIG): This source will follow close behind the former and act on existing seas. A shortwave trough is modelled to rapidly develop into a low on Tuesday and Wednesday as it swings around a large cyclonic gyre over the central Pacific. A broad fetch of 45-55mph winds will be carried eastward over a distance of 1,700nm over 40-44 hours. A separate area of extreme winds of 55-70mph associated with the deep low will have fair aim. These winds will track ENE as it passes the dateline late Wednesday. The intensity, length, duration, and proximity of the fetch spell XL surf. Long period forerunners of 18-20 seconds from the WNW should arrive late Friday afternoon. Surf will rapidly rise towards dusk to 6-8’+ by last light. The peak is predicted at near dawn on Saturday well into the XL category at 15-20’ at the outer reefs. Surf will drop to 12-18’ by the afternoon. Heights will decline more rapidly on Monday from 8-12’ early to 6-8’ occ 10’ in the afternoon.

Next: Models develop a significant subtropical low roughly 1,300nm East of Hawaii on Wednesday. Winds on its northern flank could increase to 30-40mph as it tracks NW. Surf from this source will begin to trickle in early Sunday from the ENE but be largely overshadowed by the aforementioned swell. The swell will tilt more NE early next week at shorter periods of 10-12 seconds with heights rising to 2-4’+, albeit still largely overshadowed.

Finally: Models depict another low originating off the coast of central Honshu early Thursday. This compact low is projected to rapidly deepen and gain winds of 50-65mph as it tracks eastward. Unfortunately, it will likely curve poleward much sooner in its track than the previous storm. Forerunners of 16-18 seconds from the WNW should arrive predawn Monday with surf rising to 6-10’ by midday. Heights should fall to 4-6’ on Tuesday.

South Shores: Small surf coming this weekend…

Recent/Now: A storm with an extensive fetch of 30-40mph winds East of New Zealand on January 6-7 brought 1-2’ surf over the weekend. This swell is on its way out, and surf will be down to traces on Monday. It should remain tiny through Thursday.

Next: Last Wednesday, a similar looking storm evolved East of New Zealand, reaching peak intensity on Friday. This could bring 1’ occ 2’ surf for Friday and Saturday before surf returns to flatness next week.

Finally: The XL WNW swell for Saturday could bring 1-3’ West wrap to select spots, likely largest from the morning to midday.

East Shores: Subtropical storm swell next week?

Recent/Now: Surf has been very small at 1-2’ or less in recent days with subtle ups and downs from large WNW-NW swells wrapping over. Wind swell has been nonexistent as the trade winds are too far upstream of Hawaii. Surf will remain at 2’ or less through Friday.

Next: AN XL WNW swell could bring small wrap of 1-2’+ to exposed spots on Saturday.

Finally: Easterly winds will begin to strengthen well upstream as a subtropical storm intensifies on Wednesday. On Thursday and Friday, the low will track NW as the fetch gets closer and closer. By Sunday, models show the low taking a SW jog towards Hawaii with 30-40mph winds. Seas of 22’ could reach to within 800nm of Hawaii. Surf will from the ENE rise late Saturday with the period increasing from 8-9 seconds to 10-12 seconds by Sunday at 1-3’. Surf should be 1-2’ occ 3’ on Monday as the direction switches NE. The SW track of the low should increase heights a couple notches for Tuesday to 3-5’. There is high uncertainty at this time as the event is still quite far out in time and the storm has not yet developed. Stay tuned to SNN.

Tropics: Nothing for this 7-day outlook.

Surf Climatology HERE

NEW 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) 10 Feet (up 2′) and (warning) 15 Feet

East-Facing Shores – 10 Feet (up 2′) 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).

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