Big Picture
BIG Picture updated 1230pm, Sunday, October 20
Monday, October 21st – Tuesday, October 29th
Much lighter winds with mostly dry weather this week…
The synoptic scale pattern this week over the North Pacific is starkly different than last week’s. A robust ridge of high pressure is building over the central North Pacific with an area of low pressure deepening about 900 nautical miles NW of Hawaii. This feature is close enough to the islands to affect the local trade winds. East trades should decrease from moderate paces (10-20mph) on Sunday to light to moderate paces (5-15mph) on Monday. Speeds should decline to light paces (5-10mph) from Wednesday to Friday with fairly widespread sea breezes possible in the afternoon. This will be especially true on Friday and Saturday when a surface trough forms inside of 500nm of Hawaii, which will cause the flow to turn SE. The disturbances should fill in towards early next week, allowing more typical moderate to fresh (10-25mph) paced trades to return. Mostly dry weather conditions will prevail this week, but showers could return by late in the weekend or early next week.
Surf Outlook –
North Shore and West Shores: A mix of NW, NNW, and NE swells this week…
Recent/Now/Next: Surf on Sunday was 1-3’ Hawaiian scale on a 10-12 second period NW swell. The source was an area of low pressure that tracked eastward from the Kamchatka Peninsula to the dateline Oct 13-15 with 30-40mph winds on its southern periphery. Surf from this swell peaked on Saturday at 2-3’ and is dropping on Sunday. The storm stalled just east of the dateline Oct 17 and the fetch winds on its western periphery aimed at Hawaii accelerated to 30-40mph. It should bring a reinforcing 10-12 second period NNW swell that will keep surf at 1-2’+ on Monday. Surf from this source should drop to 1-2’ on Tuesday. A 10-13 second period NE swell will become one of the primary sources of 2’ surf through at least Sunday. The peak day should be Saturday at 3’+ at the focal reefs. More on this in the East Shores section.
Next: A very large, broad storm entered the northern Bering Sea Oct 20. Although most of its exceptionally wide fetch was confined to north of the Aleutian Islands, a portion of it dragged across the NW corner of the North Pacific with satellite confirmed winds of 40-50mph. Proximity and fetch distance/duration will limit surf potential. Moderate period forerunners of 15-16 seconds from the NW should arrive during the day on Thursday. Surf should peak Friday at 1-2’+ and drop to 1-2’ on Saturday.
Finally: Models predict a system diving into the Gulf of Alaska Oct 24-25 with 40-50mph winds aimed highest east of Hawaii. Angular spreading should enable a portion of the swell to clip the islands. Exactly how big that would translate to surf is highly uncertain this far out. At this point, surf from the NNW could begin rising as early as Sunday with surf peaking at no larger than 4’ on Monday.
Outlook: It should be rather slow-going heading into the beginning of November. High pressure is favored to remain in place over the central and eastern North Pacific, which would limit fetch length and proximity to Hawaii. Of interest is tropical activity in the western Pacific. The GFS model has been consistent is depicting a typhoon tracking northward from near the Mariana Islands before curving eastward Oct 26-Nov 1. This could bring some longer period W-WNW swell as early as November 3.
South and West Shores: A small bump in surf around midweek and again over the weekend…
Recent/Now/Next: Surf on Sunday was 1-1.5’ on a 15-16 second period SW swell. The source was a system that hugged the coast of Antarctica as it tracked eastward from well south of SE Australia Oct 13. It aimed winds of 40-50mph at the Tasman Sea. The system then passed south of New Zealand and continued to aim similar winds to the NE Oct 14-15. On Oct 15, a longwave trough aligned with the equatorward side of this system and lengthened the fetch much further north. Although winds along this portion of the fetch were weaker at 25-35mph, the proximity to Hawaii decreased substantially. Surf from this swell should drop later on Monday before rising again from the SSW. Surf from the SSW should hold at 1-1.5’ on Tuesday and potentially rise a half notch to 1-occ. 2’ later Wednesday into Thursday with a 13-14 second period. Surf from this source should drop on Friday to 1-1.5’.
Finally: A more powerful storm deepened 1,500nm SE of New Zealand on Oct 18. It made a slight NE jog Oct 18-19 with a wide fetch of 45-55mph winds aimed highest east of Hawaii. Long period forerunners of 18-20 seconds from the South should arrive early Friday. Surf should rise to 1-occ. 2’ for the second half of the day and peak on Saturday at 1-2’ occ. +. It should be similar on Sunday and slowly drop early next week.
Outlook: Models keep a series of weak systems passing south of the Tasman Sea and New Zealand October 21-24 which should keep surf at near the background level heading into early November. After October 24, the South Pacific could become very quiet and lead to a prolonged period of surf below the background level (1’ or smaller) beyond November 2.
East Shores: Sizable NE swell coming towards this weekend…
Recent/Now/Next: Surf on Sunday was 1-2’ on a small 5-6 second period East trade wind swell and trace amount of North wrap. Surf from the trade wind swell should drop to 1-1.5’ on Monday. The trade wind swell should be nonexistent from Tuesday to Sunday due to weak trades over and upstream of Hawaii. Surf from an East trade wind swell could begin rising next Monday and Tuesday towards 1-2’ as the local winds increase.
Next: A subtropical system centered 900nm NW of Hawaii began to slowly deepen over the weekend. This trend should continue into early in the week. The surface pressure gradient between the deepening system and a building ridge over the central North Pacific will tighten. Winds will naturally blow from the ridge to the trough in a northeasterly direction. By late Monday, the area of enhanced NE winds will extend eastward to NNE of Hawaii. Small 8-10 second NE swell should arrive on Tuesday and bring surf back up to 1-2’ into Wednesday.
Next (MODERATE): By Oct 22-23, models rapidly pinch off from the eastern periphery of the NE fetch an intense storm centered 1,300nm NE of Hawaii. The nearly stationary system should gain storm-force winds of 50-65mph that will be aimed at Hawaii. It should rapidly weaken on Oct 24. 15-17 second period forerunners from the NE should arrive Friday afternoon and quickly rise overnight. It should peak over the first half of Saturday at 3-5’ (4.5’ of swell at 12-13 seconds). The light and variable local winds predicted for that morning over the windward coast should lead to excellent morning surf conditions. Surf should steadily drop to 1-3’ on Sunday. Small North wrap from a swell impacting the North shore could keep surf at 1-2’+ on Monday, Oct 28.
Finally: The National Hurricane Center predicts with high probability that remnants of Tropical Storm Nadine will reform over the eastern North Pacific early this week after transiting westward over southern Mexico. The GFS and ECMWF models depict a compact tropical storm or hurricane tracking E-ENE through Sunday. It could bring a long-medium period, small to moderate ESE-East ground swell as early as next Monday.
Outlook: The remnants of the aforementioned tropical cyclone could become absorbed into the trade wind regime early next week and significantly enhance trade wind swell. Surf could steadily rise over the last few days of October and the beginning of November to well above average (approaching advisory level). Stay tuned…
The next SNN Big Picture will be issued on Sunday, October 27.
Forecaster Jonathan Huynh
Surf Climatology HERE
