COLLABORATIVE NEARSHORE SWELL AND WIND FORECAST FOR OAHU
NWS/NCDDC HONOLULU HI
224 PM HST MON APR 24 2017
THIS COLLABORATIVE FORECAST WILL BE UPDATED MONDAY THROUGH FRIDAY AT
300 PM WHEN PAT CALDWELL IS AVAILABLE/
Oahu Surf Climatology
|SWL HGT||OPEN OCEAN SWELL HEIGHT MEASURED FROM TROUGH TO CRESTIN FEET LOCATED 20 NAUTICAL MILES OFFSHORE|
|DMNT DIR||DOMINANT DIRECTION TYPICALLY +/-10 DEGREES IN 16 COMPASSPOINTS|
|DMNT PD||DOMINANT PERIOD IN SECONDS|
|H1/3||SIGNIFICANT WAVE HEIGHT IN THE SURF ZONE|
|H1/10||AVERAGE HEIGHT OF THE HIGHEST ONE-TENTH WAVES IN THE SURFZONE|
|HGT TEND||HEIGHT TENDENCY OF SWELL (VALID VALUES: UP/DOWN/SAME)|
|PROB||PROBABILITY OF OCCURRENCE (VALID VALUES: HIGH/MED/LOW)|
|WIND SPD||OPEN WATER WIND SPEED MEASURED IN KNOTS LOCATED20 NAUTICAL MILES OFFSHORE|
|WIND DIR||WIND DIRECTION IN 16 COMPASS POINTS|
|SPD TEND||WIND SPEED TENDENCY (VALID VALUES: UP/DOWN/SAME)|
SURF HEIGHTS WILL VARY BETWEEN DIFFERENT BEACHES AND AT THE SAME
BEACH AT DIFFERENT BREAK AREAS.
Discussion: summary, short period surf from WNW through the week and longer period SSW going into the weekend.
Detailed: Mid Monday on northern shores has declining breakers from 350-020 degrees. A small event is due overnight.
A low pressure tracked from northern Japan to the central Aleutians on the dateline 4/19-21 with strong to near gale winds about 2000 nm away and peak seas of 12-15 feet. Nw Hawaii NOAA buoys show an increase in the 11-13 second band wave energy Monday morning 4/24. This small event from 300-320 degrees is expected to fill in late Monday and hold Tuesday.
There was an increase in surface winds just west of the dateline 4/22-23 associated with this same low pressure near the Aleutians. Peak winds were near gales. This could bring the surf up to near the spring average on Wednesday from 310-320 degrees. It should drop below average Thursday from the same direction.
A front followed by a strong surface high pressure cell is modelled to push towards Hawaii from the dateline 3/26-28. Strong breezes over the 330-360 degree band are expected to bring a NNW to N windswell picking up Saturday.
Mid Monday on eastern shores has low breakers. Trade windswell is expected to remain below average on Tuesday.
Surface high pressure of near 1026 mb near 30°N, 140°W 4/24 has a fetch of moderate trades well east of Hawaii reaching westward to Oahu. This should keep similar low windswell through the week.
See the latest NWS state forecasts discussion regarding the changing local winds and weather going into the weekend. Windswell from NNW to NNE is expected over the weekend with a veering trend.
Mid Monday on southern shores has seasonal background surf. Similar conditions are likely for Tuesday.
Strong trades in the southern hemisphere should keep below average, shorter-period breakers from 140-170 degrees 4/24-26. Longer period swell from 208-220 degrees from systems a week ago in the southern Tasman sea could add low, inconsistent, longer period swell 4/24-26.
A more favorable pattern for surf in Hawaii formed 4/19 with low pressure system S to E of New Zealand. This should bring surf above the summer average late in the week.
For Thursday, surf is expected from two sources. A front backed by gales pushed NE to the E of New Zealand 4/19-20 nosing to near 3700 nm away. This should add below average surf from 185-200 degrees building Thursday.
A second source was further away though much broader and stronger. A storm-force system with central pressure to 951 mb tracked ENE from near 60s to the SE of New Zealand 4/20-22. It had a wide fetch of gales to storm-force winds about 4500 nm away.
The pacioos/cdip american samoa buoy is starting to show long period forerunners in the 18-22 second band from this source 4/24. This long period energy is expected to slowly fill in locally 4/27 with inconsistent sets. It usually takes about a day for remote sources to fill in with more consistent sets. The event should continue to build Friday 4/28 from 185-200 degrees, peak Friday night, then slowly drop over the weekend.
Into the long range, a series of low pressures with severe gales aimed mostly at the Americas south of New Zealand 4/23-24. It was close enough to the great circle route to Hawaii for angular spreading to bring in surf at or above the summer average within 5/1-3 from 180-200 degrees.
In the northern hemisphere, models show a compact gale tracking NE to the east of the dateline 4/30-5/1 that could bring a spring average NNW event locally roughly 5/2.
Breakers from trade windswell are modelled to be below average 4/30-5/2.
Long range forecasts are subject to major revisions.
This collaborative forecast will resume on Wednesday, April 26.
This forecast was produced through the collaborative efforts of NWS and ncei. Please send suggestions to email@example.com or call the Warning Coordination Meteorologist at 808-973-5275.
Additional resources: see /in lowercase/ http://www.prh.noaa.gov/hnl/pages/marine.php.
NWS Forecaster BURKE and NCEI PAT CALDWELL