Big Picture
BIG Picture updated 1030am, Sunday, July 21
Monday, July 22nd – Tuesday, July 30th
Stronger trades and enhanced showers this week…
A ridge of high pressure centered over the east-central North Pacific will expand and strengthen through the week to near 1038-1039 millibars. Over the weekend, the trades were from the East at moderate paces (10-20mph) and light enough for afternoon sea breezes to develop over the leeward coasts. The winds will shift ENE and increase to moderate to locally fresh paces (10-20+mph) for Monday as a weak disturbance approaches the islands from the East. Speeds should reach fresh paces (15-25mph) Tuesday and Wednesday and peak on Friday at fresh to strong paces (15-30mph). It should slowly drop over the weekend and early next week as the ridge shifts westward and flattens out a notch.
An approaching disturbance could enhance trade wind shower activity Tuesday and Wednesday. A more typical regime of trade wind showers will resume thereafter and hold through the end of the period. The National Hurricane Center is monitoring a few tropical areas of interest over the eastern North Pacific over the next week.
Surf Outlook –
North Shore: Rising trade wind swell wrap for select spots…
Recent/Now/Finally: Surf on Sunday was 0-1’ Hawaiian scale on a 6-8 second period NNW-N swell. The source was a weak, compact system that strengthened as it passed the dateline and approached the Gulf of Alaska Jul 17-18. Peak winds were 25-35mph but were aimed mostly NE of Hawaii. Surf from this source should drop to below traces on Monday. The trade wind swell wrap will become the dominant source of surf beginning Monday and Tuesday and lasting through early next week. The wrap should gradually increase through the week and peak Friday and Saturday and slowly drop early next week. Top spots for trade wind swell wrap such as Laniakea could see surf up to near 2’ on the peak days.
Outlook: Trades could significantly weaken towards early Aug. This would cause trade wind swell wrap to drop to traces or smaller, and flat conditions could take hold for all North Shore breaks at the start of next month.
South and West Shores: Numerous sources of background level surf from the SW-SE…
Recent/Now: Surf on Sunday morning 1-occ. 2’ on a 12-13 second South swell and traces of an 8-9 second SSE swell. The source of the South swell was a trough over the central South Pacific from Jul 12-13 that directed a narrow fetch of 35-45mph to the north. The fetch traveled towards the subtropics into Jul 14, but the wind speeds drop to 25-35mph. Surf from this source should hold into Monday and slowly drop towards midweek. The source of the SSE swell was more difficult to identify and was likely from the trade wind belt of the South Pacific last week.
Next: A subtropical system over the central South Pacific gained near storm-force winds on Jul 15. It gradually broadened, and winds dropped to 30-40mph as the storm tracked ESE Jul 16-17. 11-13 second period energy from the S-SSE should arrive overnight Sunday and keep surf at 1-occ. 2’ Monday and Tuesday before dropping to traces midweek.
Next: A storm-force trough hugged the northern coast of Antarctica Jul 14 before pulling northward Jul 15-16. By the time it aimed a wide, substantial fetch to the NE, the system was at the far eastern edge of the Hawaii swell window. It could still bring low, long period South swell Monday and Tuesday resulting in surf of 2’ or smaller.
Next: Another large trough hugged Antarctica Jul 15 but nudged northward over the central South Pacific Jul 16 with a wide fetch of 35-45mph winds. There is slightly better surf potential from this source because the fetch was aimed equatorward from further to the west and more within the Hawaii swell window. It could bring low, long period South swell and keep surf at 2’ midweek.
Next: Yet another trough with fetch winds of 40-50mph gained some northward extent Jul 17-18. Its starting location was even further west than the previous two systems. Low, long period energy could arrive late Thursday. Surf from the South should rise to 1-2’ occ. + on Friday and slowly drop Saturday.
Next: Another subtropical system formed in the central South Pacific and gained near storm-force winds over a narrow fetch aimed at Hawaii Jul 18-19. It could bring 11-13 second energy from the S-SSE Friday and Saturday in the form of 1-occ. 2’ surf. The system then set up a very long, wide fetch of 30-35mph winds aimed almost directly north to its east Jul 20-21. This should bring surf from the South of 1-1.5’ in place Sunday and Monday.
Next: A larger, more powerful system developed NE of New Zealand Jul 19-20. As is common with many of these subtropical systems, the fetch of storm-force winds was short and narrow. It should bring 1-occ. 2’ surf from the SW Friday through Sunday.
Finally: A ridge pressed against the coast of Chile and generated a long, wide fetch of 20-35mph winds reaching into the subtropics of the eastern South Pacific Jul 18-21. It could bring 9-12 second period SSE-SE swell from Friday to early next week and surf of 1-1.5’
Outlook: The storm track could become more favorable for local surf Jul 23-24 as a system develops near New Zealand. It could bring surf back to near the summer average from Jul 31 to Aug 2.
East Shores: Surf rising to above average by Friday and Saturday…
Recent/Now/Finally: Surf on Sunday was 1-occ. 2’ and slowly rising from the East trade wind swell in the 4-7 second period band. Heights should rise to 1-2’ on Monday, 1-2’+ on Tuesday, 1-3’ on Wednesday, and 2-3’ on Thursday due to strengthening trades over and upstream of the islands. The swell direction will shift ENE in the first few days of the week. It should peak Friday into Saturday above average at 2-3’+ and slowly drop on Sunday. Surf should hold around average (1-3’) early next week.
Outlook: The trade wind pattern could weaken significantly heading towards Aug. This would bring surf to well below average at 2’ or less to start the new month.
The next full SNN Big Picture will be issued on Sunday, July 28.
Forecaster Jonathan Huynh
Surf Climatology HERE
