Big Picture
BIG Picture updated 5/18 at 415pm
Monday, May 19th – Tuesday, May 27th
Moderate to fresh paced trades all week, shifting from the East to ENE to NE…
Over the weekend, two large areas of high pressure sat over the western and eastern North Pacific. In between was a weak trough roughly 800 nautical miles NW of Hawaii. The eastern Pacific ridge brought moderate to fresh (15-25mph) East trade winds. Over the next several days, the trough will shift westward while the high pressure area over the western Pacific will slowly meander eastward and eventually merge with the one to the east, forming a larger high pressure center. The trades will shift ENE through midweek and NE late in the week into the weekend and hold at similar spaces through the week. By late in the weekend into early next week, models depict a large cyclone forming over the Gulf of Alaska with a cold front helping to weaken a ridge over the islands. This could weaken the trades slightly late in the weekend into early next week.
Trade wind showers will become more isolated on Monday and Tuesday but pick up from midweek to the weekend, favoring overnight and morning hours. They should trend down again early next week.
Surf Outlook –
North Shore and West Shores: Miniscule surf this period but monitoring small potential towards the end of May…
Recent/Now: Surf on Sunday was 0-1.5’ Hawaiian scale on a mix of a holding 10-11 second period NNW swell and dropping trade wind swell wrap. The source was a weak trough south of the central Aleutian Islands that aimed a fetch of 25-30mph winds at Hawaii May 16. Surf from the NNW swell should drop to 0-1’ on Monday. The trade wind swell wrap should keep favored spots at 0-1’ maybe occ. 1.5’ through the week on peak days.
Next: Another weak trough began to nudge towards the SE from the central Aleutian Islands May 18. It should dissipate May 19 after aiming 25-30mph winds towards Hawaii. It could bring a tiny bump in surf to 0-1.5’ early Wednesday. Surf should drop to 0-1’ on Thursday and Friday.
Finally: A stronger system will unfold May 19-20 as it occludes over the eastern Aleutian Islands and stretches eastward with a narrow fetch of 30-35mph winds aimed nearly zonally to the east. WaveWatch 3 indicates a possibility of 14-16 second period energy from the NW arriving late Friday. Surf could peak at 1-1.5’ on Saturday and drop to 0-1.5’ on Sunday and 0-1’ on Monday and Tuesday.
Outlook: Storm activity over the North Pacific will be minimal May 21-23. Longer range model output reveals a potentially stronger system confined to the NW corner of the North Pacific May 23-24 that may develop fetch winds of near storm-force intensity. It could bring head-high surf or larger (2-3’+) towards May 28-30. Stay tuned…
South Shores: Periods of small to fun surf all week long…
Recent/Now (Summer Background): Surf on Sunday was 1-2’ occ. + on a 16-17 second period SSW swell. Long period forerunners of 20-22 seconds from the SSW arrived late Friday. Surf rose to 1-2’ occ. + by late Saturday. The source was a cyclone that passed south of New Zealand May 10 with a long, wide fetch of 40-50mph winds aimed to the ENE. It weakened May 11. Surf from this swell should be similar, perhaps a half notch smaller, on Monday.
Next (Summer Background): The next storm clipped the southern side of New Zealand as it tracked eastward May 11-12. By May 13, it aimed a wide fetch of 35-45mph winds to the NE, which inched northward and closer to Hawaii into May 14 as it scooted eastward. 17-18 second period forerunners from the SSW should arrive Tuesday morning. Surf should rise to 1-occ. 2’ late Tuesday and peak Wednesday into Thursday at 1-2’ occ. + as the swell angle shifts to the South. Surf from this swell should drop to 1-occ. 2’ on Friday.
Finally (Summer Average?): The same system redeveloped into a large monster with 55-70mph winds aimed to the NNE over the east-central South Pacific. However, it likely had already tracked to the east of the Hawaii swell window, so energy from this system is unlikely to affect Hawaii. Further to the west, a very wide system passed south of the Tasman Sea May 14-16 with 40-50mph winds, though the aim was fairly zonal and less than favorable for Hawaii surf. The fetch extended to SE of New Zealand May 15-16, when the aim became a little more favorable. These winds also acted upon existing seas. Unfortunately, the American Samoa buoy went offline May 3 and will be unable to preview the incoming swell. Furthermore, at the time of this writing, the NOAA webpage responsible for visualizing satellite altimetry data was offline, so the significant wave heights generated by this system could not be compared to WaveWatch 3 output, which analyzed 35’ seas south of the Tasman Sea on May 15. Very long period forerunners of 20-22 seconds from the SW could arrive as early as Thursday. Surf from the SW should rise to 1-2’ occ. + early Friday. Surf from the SW-SSW could reach 1-2’ occ. 3’ late Friday into Saturday, though confidence is low. Surf from the SSW of at least 1-2’ occ. + should persist through the weekend and drop early next week.
Outlook: The South Pacific went quiet May 17-18 as high pressure became centered east of New Zealand. By May 19, a series of small pulses will pass east of New Zealand and could bring a couple of small bumps during the final week of May, though nothing larger than 2.5’ on peak days as an area of high pressure over New Zealand depresses storm activity. A much more substantial system could set up a very long fetch of 40-50mph winds aimed to the NNE-NE from east of New Zealand May 23-24 that could deliver above average surf (2-3’ occ. 4’?) towards the end of the month.
East Shores: Near average surf to start but generally smaller for most of the week…
Recent/Now/Next/Finally: Surf on Sunday was 1-3’ on a 9 second period East trade wind swell thanks to fresh paced trades upstream of the islands over the last few days. Surf should drop to 1-2’+ by Tuesday as the local and upstream winds weaken a notch. Models differ on the intensity of the upstream trade winds later in the week: the GFS model increases the speeds while the ECMWF model maintains or lowers the speeds. At this point, expect near average surf of 1-2’+ or 1-3’ to continue through the period. Confidence increases that surf will drop to below average next week.
Outlook: After a likely low spell between May 26 and May 30, models show an increase in trade wind speeds. Surf could rebound to near average by the end of the month or early June.
Forecaster Jonathan Huynh
Surf Climatology HERE
