Pat Caldwell

Outlook
Outlook through Thursday April 30: a new northwest swell will arrive late Sunday and rapidly build Sunday night. This swell will veer northerly and peak Monday into Tuesday with surf near advisory levels for north and east facing shores. 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
No high surf advisory or warnings.
Forecast
Surf along east facing shores will be 4 to 6 feet tonight, and 3 to 5 feet Saturday. Surf along south facing shores will be 3 to 5 tonight, and 2 to 4 feet Saturday. Surf along north facing shores will be 1 to 3 feet through Saturday. Surf along west facing shores will be 1 to 3 feet through Saturday.
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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: south and east side trending down on the weekend with short-lived N event Monday. Detailed: mid Friday on northern shores has tiny to small breakers from short-period energy of west- and east-components. Similar surf is likely for Saturday. See comments below for eastern shores for the trade windswell trend. A weak low pressure tracked east from northern Japan 4/18, reaching the dateline 4/21. Winds were fresh to strong with pockets of near gale beyond 1500 nm away. The low pressure occluded near east of the dateline 4/21-22, with winds aimed at Hawaii dropping to fresh or less. The pacioos/cdip Waimea, Oahu nearshore buoy 4/24 shows an upward trend in the 10-12 second band within 290-315 degrees. This weak, short-period event should hold about the same on Saturday and fade out on Sunday from the same direction, at levels lower than the easterly windswell at select locations. A gale low formed in the Bering Sea 4/21 east of Kamchatka. It tracked east 4/21-24, with gales hugging the southern side of the Aleutian islands west of 175°E. Winds weakened as the fetch approached the dateline late 4/23. With the travel distance over 2200 nm, local surf potential is low for this source out of 325-340 degrees. Low, moderate-period swell of 15-17 seconds is expected to fill in locally Sunday afternoon. Surf from a closer source is expected to override it on Monday. The weak area of low pressure W to NW of Hawaii 4/22-24 is modelled to be pulled north by the weather pattern associated with the Bering Sea low 4/24-25. Models show a compact area of marginal gales on the NW to N side of the nearby low as it tracks to the NE past the longitude of Oahu late Saturday. A strong surface high pressure is modelled to push east from the dateline 4/25-26, adding a large area of strong breezes with pockets to near gale, nosing down to within 500 nm of Hawaii. The swell generation from within 330-010 degrees should be east of the Hawaii swell window by late Sunday. Proximity makes for a sharp rise in surf. Heights should climb rapidly Sunday night from 330-350 degrees into Monday at levels near to a notch above the September to may, north shore seasonal average, which is 12 feet peak face for refractive zones on the common, though less frequent, higher sets, or h1/10. The north component, shorter-period swell from 330-010 degrees should trend down steadily below average on Tuesday, and linger at small levels on Wednesday. Mid Friday on eastern shores has breakers above the trade windswell average from 70-100 degrees. Heights should lower on Saturday. Surface high pressure centered near 35°N, 140°W has held position with a slow weakening trend 4/21-24. It set up a wide, long fetch of fresh to strong breezes nosing up to near Oahu. Ascat satellite showed a large area of strong breezes still holding late on Thursday 4/23 in an an area about 800 nm away. This upstream source should keep the dominant wave period of the windswell on the long side of the spectrum through the weekend. With weakening local winds 4/25, the deep water wave heights are predicted to lower, though surf potential remains active due to the longer wave periods. Surf from 70-90 degrees should remain near to above average on Saturday, fall near to below average on Sunday, then drop below average as it fades on Monday as more northerly-component windswell builds. See the latest NWS state forecast discussion regarding the evolving winds and weather this weekend into early next week. North exposures of the east side should have above average breakers on Monday from the nearby source described above. A new strong surface high pressure cell is modelled north of Hawaii 4/26-29. Models show an area of strong breezes over the 30-60 degree band aimed at Oahu late Sunday into Monday within about 200-700 nm out to the NE. Combining with the nearby generated windswell, height should be rough and above average on Tuesday from within 30-70 degrees. The dominant direction of the elevated windswell should veer more to 50-80 degrees by Wednesday. Mid Friday on southern shores has surf out of 175-200 degrees above the March - October, south shore average, which is 5 feet peak face for h1/10 sets in the more refractive zones. Heights should drop to near the average on Saturday from 170-190 degrees. A large area of low pressure E to SE of New Zealand 4/13-15 was responsible for the recent above average southerly swell. Southern Hawaii NOAA buoys 51002-4 4/24 show a downward trend in dominant wave period and a gradual decline in magnitude over the 12-15 second band. Southerly events tend to linger longer since the remote source location allows the swell trains to spread out over a large area. This should keep this event one more day before conditions fall below average on Sunday. Background level surf should be the rule next week, with low odds for shorter-period S to SSE swell from a mid-latitude low south of Tahiti 4/16-19 and longer-period SW to S from lows tracking east just north of the antarctic ice sheet from Tasmania to south of Tahiti 4/16-24. Into the long range, models amplify a jet trough SE to E of New Zealand 4/28-30. This pattern suggests a return to average or above average southerly swell from within 180-200 degrees starting around 5/7. In the north Pacific, models shift the jet stream northward with minimal surf from WNW to N 4/30-5/2. Above average trade windswell is expected to continue 4/30, though trend down 5/1-2. Long range forecasts are subject to low confidence. This collaborative forecast will resume on Monday, April 27. 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
04/24
2WNW1123UP13-19ESESAME
7E968SAME
3S1447DOWN
SAT
04/25
2WNW1023SAMELOW7-10SEDOWN
5E946DOWNMED
3S1335DOWNMED
SUN
04/26
2WNW913DOWNLOW7-10VRBSAME
2NNW1635UPLOW
3E934DOWNLOW
2S1223SAMELOW
MON
04/27
8NNW121014UPLOW18-22NEUP
7NE624UPLOW
2S1223SAMELOW
TUE
04/28
6N10610DOWNLOW19-23ENEUP
9NE868UPLOW
2S1223SAMELOW
WED
04/29
3NNE1035DOWNLOW19-23ESAME
9ENE868UPLOW
2S1223SAMELOW
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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 AND NCDDC PAT CALDWELL

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