Pat Caldwell

Outlook
Outlook through Friday January 30: the large west-northwest swell will shift out of the northwest and gradually decline over the next couple of days, with all shores likely below advisory levels by Monday. A northwest swell will push surf along north and west shores around advisory levels for Tuesday night through Thursday, followed by a potentially larger northwest swell late Friday into next weekend. Surf heights are forecast heights of the face or front of waves. The surf forecast is based on the significant wave height, the average height of the one third largest waves, in the zone of maximum refraction. Some waves may be more than twice as high as the significant wave height. Expect to encounter rip currents in or near any surf zone.
Hazards
HIGH SURF WARNING FOR NORTH FACING SHORES HIGH SURF ADVISORY FOR WEST FACING SHORES
Forecast
Surf along north facing shores will be 20 to 25 feet tonight, lowering to 15 to 20 feet. Surf along west facing shores will be 12 to 18 feet tonight, lowering to 10 to 15 feet Sunday. Surf along east facing shores will be 1 to 3 feet through Sunday. Surf along south facing shores will be 2 to 4 feet with locally higher sets along west facing exposures through Sunday.
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About Collaborative Surf
This collaborative forecast will be updated Monday through Friday at 300 pm when Pat Caldwell is available.
Collaborative Surf Discussion
SURF HEIGHTS WILL VARY BETWEEN DIFFERENT BEACHES AND AT THE SAME BEACH AT DIFFERENT BREAK AREAS. DISCUSSION: Summary: west-component swell above average into Saturday as NW swell builds. Detailed: mid Thursday on westerly exposures of the south, west, and north shores of Oahu have above average, long-period swell from 270-305 degrees. A subtle decline is predicted late Thursday into Friday morning, as heights remain above average. The winter Aleutian low pressure pattern has been active this week with a counter-clockwise gyre from the surface to upper levels filling a vast area of the central north Pacific. This has been giving an extended period of above seasonal average surf of a more westerly component, which is common in January and February. The shadowing by Niihau and Kauai on Oahu leads to a more challenging task of estimating surf height, since the degree of shadowing varies from place to place along any given coast. Short-wave troughs in the jet stream on the SW to S side of the upper level gyre had low pressure troughs at the surface with about a one-day spacing. Each trough had enhanced ocean surface winds to severe gales and acted upon existing seas over the 270-305 degree band. These sources are similar, and a notch stronger, than the pattern that gave the large west swell locally of December 20-21, 2013. Thursday, January 22 is the one of the largest in the historical records for west exposures of the south shore, higher than the 2013 event. The first enhancement for the westerly-component swell crossed the dateline on Tuesday. This feature can be attributed to the exceptional westerly components that are allowing above summer average surf for select spots of the south shore on Thursday. Buoy 51101, 270 nm WNW of Oahu, shows a downward trend late morning Thursday 1/22, which is in agreement with the Wave Watch III model. A slow decline is predicted into Friday morning, though surf remaining above average on all westerly exposures. The second enhancement for the west swell reached the dateline on Wednesday. At the same time, the Aleutian low, or parent gyre, began to slowly weaken and shift east. By Thursday morning, near gales to gales have reached to within 800 nm of Oahu. This should lead to a rise late Friday, peaking early Saturday at levels that could be similar to Thursday for top south and west shore locations. The west-component swell should drop rapidly on Sunday. The Aleutian low began to feed the 300-320 degree band late 1/21 as the gyre began its eastward shift. Gales to severe gales stretched over a wide, long fetch of over 1000 nm from south of the western Aleutians, to within 1000 nm of Hawaii by Thursday morning. Models keep gales over this band into Friday with a weakening trend as the head of the fetch approaches Hawaii. Sub-gale winds closer to Hawaii are modelled to cover the 320-350 degree band, giving shorter-period surf late Saturday through Sunday, resulting in confused breakers for NW to N exposures over the weekend. The more NW surf is predicted to build on Saturday from 300-320 degrees, maintaining extra-large breakers, meaning breakers on outer reefs. It is expected to peak overnight Saturday, with marginally extra-large surf on Sunday. Heights should fall to near the seasonal average by late Monday morning, then drop to small levels by Tuesday as a new episode fills in. A new winter-caliber, low pressure system is forming east of Tokyo on Thursday. Models show it occluding east of Hokkaido, Japan on Friday with central pressure below 970 mb. It is then modelled to slowly weaken and shift east along 45°N, reaching the dateline Monday. The strongest winds are expected Friday to early Sunday over the 300-310 degree band, with the head of the fetch about 2100 nm away by Sunday morning. This should bring the 20-second wave period energy into Hawaii Tuesday morning. The long travel distance is a buffer to surf size locally. Heights are expected to build to near the seasonal average by Tuesday afternoon. See the latest NWS state forecast discussion regarding the friday-saturday frontal passage timing and strength, and affect on local winds. Small windswell from 200-270 degrees is predicted to rise Friday and drop Saturday, as the short-period energy veers on the compass to more northerly components after the frontal passage. A ridge building north of the state Sunday into Monday is modelled to return trades for a few days with a more ne-component until Tuesday when the wind direction veers more E. The upstream fetch of moderate to fresh breezes is modelled to be short, so breakers from windswell should stay near the trade windswell average or less, building Sunday and dropping Tuesday. No surf beyond tiny is expected from the southern hemisphere this period 1/22-27 and into the long range. Into the long range, the low pressure that is forming Thursday 1/22 off Japan is expected to slow and broaden east of the dateline monday-thursday. The initial WNW to NW, near to above average surf 1/28 should give way to more NNW going into the weekend. Models place low-end gales over the 320-355 degree band 1/27-29, that should make for short- to moderate-period NNW to N surf at levels near the seasonal average over the weekend of 1/30. Windswell is expected to be low 1/28-29 with light to gentle breezes. Long range forecasts are subject to low confidence. This collaborative forecast will resume on Monday, January 26. This forecast was produced through the collaborative efforts of NWS and NCDDC. Please send suggestions to w-hfo.webmaster@noaa.gov or call the Warning Coordination Meteorologist at 808-973-5275. Additional resources: see /in lowercase/ http://www.prh.noaa.gov/hnl/pages/marine.php.
Collaborative Surf Table
FORECAST
DATE
SWL
HGT
DMNT
DIR
DMNT
PD
H
1/3
H
1/10
HGT
TEND

PROB
WIND
SPD
WIND
DIR
SPD
TEND
1PM
01/22
11WNW172430DOWN4-6VRBSAME
FRI
01/23
12WNW162632UPMED13-19WSWUP
SAT
01/24
13NW142632UPHIGH13-19NNEUP
7NW846UPLOW
SUN
01/25
9NW141622SAMEMED13-19NESAME
5NNW824DOWNLOW
6NNE724UPLOW
MON
01/26
7NNW131214DOWNLOW13-19NESAME
6NE724SAMELOW
TUE
01/27
4NNW1168DOWNLOW13-19EDOWN
5WNW181012UPLOW
6ENE724DOWNLOW
Disclaimer
Collaborative Surf Table Legend

LEGEND:

SWL HGTOPEN OCEAN SWELL HEIGHT MEASURED FROM TROUGH TO CREST IN FEET LOCATED 20 NAUTICAL MILES OFFSHORE
DMNT DIRDOMINANT DIRECTION TYPICALLY +/-10 DEGREES IN 16 COMPASS POINTS
DMNT PDDOMINANT PERIOD IN SECONDS
H1/3SIGNIFICANT WAVE HEIGHT IN THE SURF ZONE
H1/10AVERAGE HEIGHT OF THE HIGHEST ONE-TENTH WAVES IN THE SURF ZONE
HGT TENDHEIGHT TENDENCY OF SWELL (VALID VALUES: UP/DOWN/SAME)
PROBPROBABILITY OF OCCURRENCE (VALID VALUES: HIGH/MED/LOW)
WIND SPDOPEN WATER WIND SPEED MEASURED IN KNOTS LOCATED 20 NAUTICAL MILES OFFSHORE
WIND DIRWIND DIRECTION IN 16 COMPASS POINTS
SPD TENDWIND SPEED TENDENCY (VALID VALUES: UP/DOWN/SAME)
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NWS FORECASTER AND NCDDC PAT CALDWELL

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