Big Picture

BIG Picture updated 7/13 at 145pm

Monday, July 14^th – Tuesday, July 22^nd

Briefly lighter trades to start, then ticking up for the rest of the week…

For the large-scale picture, an extended ridge of high pressure began to split into two separate areas over the weekend, one over the western North Pacific and one over the east. The central North Pacific had weak, broad troughing. Closer to the islands, this troughing led to weaker trades compared to last week’s. The trade wind out of the ENE decreased to moderate paces (10-20mph) on Sunday, and it should be similar on Monday. Speeds should increase to moderate to locally fresh paces (10-25mph) on Tuesday, which should persist through early next week as the area of high pressure to the NE rebuilds over the central North Pacific. The weather for most of the week should be mostly dry, though a few disturbances could give a boost to windward and mauka showers on Tuesday, Saturday, and Sunday.

Surf Outlook –

North Shore: Tiny NW swell late Monday and Tuesday…

Recent/Now/Next: Surf on Sunday was 0-1’ Hawaiian scale on primarily trade wind swell wrap. Surf from this source should be similar through Tuesday, and then bump up a half notch for the rest of the period as the wind swell rebounds.

Finally: Low energy in the 11-13 second period band from the NW pinged the NW buoys on Sunday. The source was a small, weak area of low pressure that developed over the NW corner of the North Pacific. It tracked towards the dateline Jul 10 with a fetch of 25-30mph winds aimed at Hawaii. The system dissipated by Jul 11 as it crossed the dateline. This NW swell energy should arrive Sunday evening with surf peaking at 1-1.5’ on Monday afternoon into early Tuesday. Heights should fall to traces by Wednesday.

Outlook: No other significant source of surf was identified in the foreseeable future. Barring unexpected typhoon development in the tropical western North Pacific, the trade wind swell wrap should be the dominant source for the rest of July.

South Shore and West Shore: Fun swell on the way and peaking on Tuesday!

Recent/Now: Surf on Sunday was 1-occ. 2’ on a 14 second period SSW-S swell. The source was a trough that quickly traveled eastward from well SE of New Zealand to the central South Pacific Jul 3-4. It aimed a narrow band of 30-40mph winds to the NNE. This swell should have peaked overnight Saturday and should drop Monday from a more South direction.

Next (ABOVE AVERAGE): Both the Barber’s Point and Lanai buoys detected very long, 19-21 second period forerunners from the SSW-S on Sunday. The source of this swell was a larger system well SE of New Zealand that directed a wide fetch of 40-50mph winds to the ENE Jul 6-7. Satellite altimeters on Jul 7 measured seas of 30-35’, which is a couple of feet higher than analyzed by WaveWatch 3. Surf should rise to 1-occ. 2’ by early Monday, 1-2’ occ. + in the afternoon, and 1-2’ occ. 3’ by early Tuesday. It should peak late Tuesday at 2-3’ occ. +, drop to 1-2’ occ. 3’ on Wednesday, 1-2’ occ. + on Thursday, and 1-occ. 2’ on Friday.

Finally (AVERAGE): A rather large system traveled over the Tasman Sea Jul 10-12 with a long, narrow fetch of 40-50mph winds aimed to the NE. Satellites confirmed seas of just over 30’, in line with WaveWatch 3 guidance. Long period forerunners of 17-19 seconds from the SW should arrive during the day on Friday. Surf should rise to 1-2’ occ. + early Saturday and peak late Saturday into early Sunday at 1-2’ occ. 3’. Surf should drop to 1-2’ occ. + early Monday.

Outlook: A weaker trough passed over the Tasman Sea Jul 13. It had lighter winds of 30-35mph aimed to the NE and will weaken on Jul 14 as it passes over New Zealand. This will keep small surf from the SW in place through Jul 22. Models predict a couple of weak systems near New Zealand and a larger system confined to the central and eastern South Pacific around mid-month. Surf from the SSW and SSE should be no larger than the summer background level (1-2’ occ. +) towards the final week of July.

East Shores: Slightly smaller wind swell to start the week but rebounding to average and above average…

Recent/Now/Next/Finally: Surf on Sunday was 1-2’+ on an 8-second period ENE trade wind swell. The locally weaker trades should cause surf to drop to 1-2’ on Monday and early Tuesday. Slightly stronger trades thereafter should bring surf back to average levels of 1-3’ from Wednesday to Friday. A fetch of stronger trades upstream of Hawaii will nudge closer towards the end of the workweek and drive surf up to 2-3’ over the weekend and into early next week.

Outlook: A steady trade wind regime will likely continue into the latter part of the month and keep surf at near average levels at a minimum towards the end of July. Confidence is increasing that the tropical eastern North Pacific will be quiet for much of this month, lending minimal potential for tropical groundswells for the islands.

The next SNN Big Picture will be issued on Sunday, July 20.

Forecaster Jonathan Huynh

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 wehich 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).