Big Picture

SNN BIG PICTURE: Updated 745pm, Sunday, October 1st

Monday, October 2nd – Tuesday, October 10th

Light and variable into midweek, then light trades into next week…

Sunday was the last day of moderate to fresh E-ENE trades for quite a while. During the weekend, a progressive cold front began to approach from the NW. As a result, the ridge of high pressure over the central North Pacific began to get quashed. Trades should weaken to light paces on Monday. By Tuesday, the front will be due north of Hawaii, and winds will become light and variable. Afternoon sea breezes, especially over the leeward coast, will develop. This pattern will hold into Wednesday as the front washes out. By Thursday, a weak ridge will develop over the region, and light E-ENE trades should return. Paces will remain light into early next week as a series of systems passing over the North Pacific keeps the ridge weak. A drier than normal period of weather appears likely this week and weekend.

Surf Outlook –

North Shore: Progressively larger NW-NNW swells this week…

Recent/Now: Surf on Sunday rose from 0-1.5’ Hawaiian scale in the morning to 2-3’ in the afternoon. The source was a system that rapidly deepened 800 nautical miles south of the central Aleutian Islands as it swung eastward and past the dateline last Wednesday, Sep 27. Scatterometers measured storm-force winds (55-70mph) late Thursday as the system began to track NE just east of the dateline. Long period forerunners of 17-19 seconds from the NW-NNW arrived predawn Sunday. Surf should peak overnight into early Monday morning at 2-3’+. Surf should drop to 2-3’ by late Monday and 1-2’+ early Tuesday.

Next (MODERATE): Another similarly sized system followed in nearly identical footsteps of the storm that preceded it. However, it developed winds of 40-50mph much earlier in its track starting from between northern Honshu and Hokkaido last Thursday. It tracked straight east and slowly weakened. It crossed the dateline late Saturday as a weaker system but at a closer distance to Hawaii. It is modelled to stagnate and enter a second phase of intensification on Monday due north of Hawaii. 45-55mph winds should be aimed from 1,400nm NNW of Hawaii on Monday. The storm should then gradually weaken as it lifts poleward into the Gulf of Alaska. Forerunners of 17-18 seconds from the NW should arrive after midnight Monday. Surf should slowly rise to 1-2’ early Tuesday and then become the dominant swell by the afternoon at 1-3. Surf should gradually shift NNW on Wednesday as the first phase of the event peaks at 3-4’+. Reinforcing energy from the second intensification phase should arrive late Wednesday from the NNW. Surf should peak on Thursday at 3-5’+. Surf should drop to 3-4’+ early Friday, 2-3’ early Saturday, and 1-2’ on Sunday.

Finally: A broad system is predicted to track into the NW corner of the North Pacific late Tuesday with a long, wide fetch of 25-35mph winds. It should dissipate before reaching the dateline by late Wednesday. Proximity and fetch intensity will be the limiting factors. It should bring tiny 1-2’ surf Sunday into Tuesday from the NW.

Outlook: The North Pacific will likely continue its active pattern into the middle of October and possibly beyond. At this point, there is moderate potential for recurving tropical cyclones that could bring significant WNW-NW swell to Hawaii towards the second third of the month. When and how large remain to be determined…

South Shore and West Shores: Small SSE-SE to start the week followed by small SW-SSW this weekend and next week…

Recent/Now/Next: Surf on Sunday was mostly 1-2’ from the SSE-SE. The subtropical trade wind belt of the southern hemisphere flared up Sep 23-26. Similar surf should continue into Tuesday.

Next: A system briefly aimed short, narrow fetch of storm-force winds at the Tasman Sea Sep 26. A more robust system nudged 30-40mph winds into the Tasman Sea Sep 28-29, though a portion of the fetch was blocked by New Zealand’s North Island. The system stretched to east of New Zealand Sep 29-30. A very tiny SW swell could arrive Tuesday and peak Wednesday at 1-1.5’. A larger SW-SSW swell could bring surf of 1-2’ occ. + over the weekend. It should drop late Sunday into Monday.

Finally: A compact system with 50-65mph winds is modelled to track east of New Zealand Oct 2. It should weaken Oct 3. 17-19 second period forerunners from the SSW should arrive late Sunday. Surf should take all day Monday to fill in. This event should peak Tuesday and Wednesday at 1-2’ occ. +.

Outlook: Models depict a series of systems passing south of the Tasman Sea and New Zealand. It could keep small to near average SW-SSW swells going into the middle to second third of the month.

East Shores: Trade wind swell fading to zero early this week…

Recent/Now/Finally: Surf over the weekend was 1-3’ from the E-ENE trade wind swell. Heights will steadily drop overnight Sunday and on Monday as the upstream and local trades shut off. Surf should be 1-2’+ on Monday and 1-2’ on Tuesday. The dominant source of surf should be North wrap by midweek with surf of 2’ or less through the period.

Outlook: Trade wind swell will be absent in the foreseeable future. Surf should be tiny and mostly come from wrap of NNW-N swells. As the North Pacific winter season ramps up, all eyes will be on deep systems N-NE of Hawaii, but, at this point, there are no significant N-NE swells on the horizon.

The next full SNN Big Picture will be issued on Sunday, Oct 8.

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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