Surf Forecast for O`ahu

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SRFHFO

SURF ZONE FORECAST
NATIONAL WEATHER SERVICE HONOLULU HI
400 PM HST WED APR 16 2014

OAHU-
400 PM HST WED APR 16 2014

Surf along east facing shores will be 5 to 7 feet through Thursday.

Surf along north facing shores will rise to 6 to 9 feet tonight and Thursday.

Surf along west facing shores will be rise to 3 to 5 feet tonight and Thursday.

Surf along the south shore will be 1 to 2 feet through Thursday.

Outlook through Tuesday April 22: the new northwest swell will lower on Friday. Another small northwest swell is expected over the weekend. Trade winds will continue to produce short period choppy surf along 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.


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SRDHFO

COLLABORATIVE NEARSHORE SWELL AND WIND FORECAST FOR OAHU
NWS/NCDDC HONOLULU HI
300 PM HST WED APR 16 2014

This collaborative forecast will be updated Monday through Friday at 300 pm when Pat Caldwell is available.

FORECAST
DATE
SWL
HGT
DMNT
DIR
DMNT
PD
H
1/3
H
1/10
HGT
TEND

PROB
WIND
SPD
WIND
DIR
SPD
TEND
1PM
04/16
10ENE10810DOWN17-21ENEDOWN
THU
04/17
5WNW15810DOWNMED13-19EDOWN
7ENE846DOWNMED
FRI
04/18
4NW1268DOWNMED17-21ENEUP
8ENE735SAMELOW
SAT
04/19
3NW1346UPLOW17-21ENESAME
8ENE735SAMELOW
SUN
04/20
3NNW1135DOWNLOW19-23ENEUP
9ENE868UPLOW
MON
04/21
10ENE979UPLOW19-23ENESAME

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)

Compass & Swell Shadow Lines for Hawaii

SURF HEIGHTS WILL VARY BETWEEN DIFFERENT BEACHES AND AT THE SAME

BEACH AT DIFFERENT BREAK AREAS.

DISCUSSION:

Summary: northwesterly swell increasing and easterly windswell decreasing Wednesday into Thursday. A new E windswell episode for later in the weekend. Southern shores below average.

Detailed: mid Wednesday on northern shores has near flat conditions with a few tiny to small forerunners starting to show from 300-315 degrees. Heights should steadily climb late Wednesday.

A severe gale tracked east from the southern Kuril Islands late Friday 4/11 along 40°N to near 170°E by Sunday 4/13. A captured fetch set up over the 300-315 degree band beyond 2000 nm away. Buoy 51101, 270 nm WNW of Oahu, shows an increase in the 15-16 second wave energy in the morning 4/16 from this WNW direction. Local surf from 300-315 degrees should peak near dawn Thursday at moderate levels and drop into Friday to small levels.

On Sunday, the low pressure cell near 40°N, 170°E tracked NNE to a position near the Aleutian islands on the dateline on Monday. Gales aimed at targets NE of Hawaii while near gales pointed at Hawaii over the 315-330 degree band reaching about 1800 nm away. This NW to NNW energy should pick up on Thursday at small to near moderate levels, giving a wide directional spread 300-330 degrees to the event by Thursday 4/17 in the afternoon.

The primary low pressure cell near the Aleutians continued to weaken and move into the Bering Sea on 4/15. A few weak low pressure cells with near gales formed near 40°N, 175-160°W and tracked ENE 4/15. This short-lived wind energy gave a reinforcement to the swell trains in an area about 1000 nm away on Tuesday. It should serve to keep the event a bit longer, with small to near moderate breakers of shorter wave periods centered on 320 degrees on Friday with a continued wide directional spread from 300-330 degrees. The event should fade out on Saturday as a new small pulse arrives.

The jet stream over the central north Pacific is going zonal, or west to east, centered near 40°N 4/16 and is expected to hold into 4/19. Such patterns are associated with below average surf locally.

A weak low pressure is forming near 35°N, 170°E on 4/16. It is modelled to be steered rapidly ENE by the zonal jet, passing well north of Hawaii on Thursday. With the compact size and marginal gale strength, added to the fast track across the great circle rays relative to Hawaii from 290 degrees Wednesday to 350 degrees late Thursday, only a minor amount of surf is expected locally. The small event is due to pick up mid Saturday from 300-320 degrees, peak Saturday night from 310-330 degrees, and drop off on Sunday from 320-350 degrees.

Mid Wednesday on eastern shores has rough, high surf from 50-70 degrees. Heights should fall to moderate levels on Thursday.

An upper level low pinched off an eddy near 145°W to the ENE of Hawaii on 4/14, creating a surface trough below it. This trough, in combination with the strong surface high pressure to its north, created a fetch of strong to near gale winds in an area about 700 nm away on 4/14. It weakened to the background trade speeds in the fresh to strong bracket by early Tuesday, then down to moderate to fresh speeds by late Tuesday as validated by the ascat satellite.

The short-lived, nearby, enhanced source over the 50-70 degree band shot up the 10-12 second wave energy locally overnight Tuesday night as measured by the pacioos/cdip nearshore mokapu buoy off Kailua, Oahu. With close sources, rises and falls are sharp. The mokapu buoy clearly shows the sharp rise that peaked around sunrise on Wednesday morning. These longer wave periods make a big difference in surf height since there is more jacking up to waves as they break as the wave periods get longer. The longer period swell within the 8-12 second band should see a steady decline Wednesday afternoon into Thursday, taking surf heights down to moderate levels.

The zonal jet 4/16-19 is predicted far enough north of Hawaii that the surface high pressure cell of moderate strength, about 1024 mb, is modelled to remain entrenched along about 30°N stretching far from west to east to the north of Hawaii, and keep a steady spell of trades hovering within moderate to fresh locally, with a subtle minimum late Thursday. This should keep average breakers from windswell out of 50-80 degrees Friday into Saturday.

Models are showing an amplifying jet ridge and strengthening surface high pressure cell to 1033 mb north of Hawaii late Saturday into Sunday, that should trend up the local trades and breakers from windswell by Sunday. Heights should build to near high levels on Sunday and low-end high levels by Monday from within 50-80 degrees.

Mid Wednesday on southern shores has below spring average surf. More of the same is predicted through the period.

Jet level ridging SE of New Zealand 4/9-15 is the main reason for the below average southerly swell. Wave watch iii shows a host of swell trains, all of low magnitude near 1 feet open ocean height, from within 140-220 degrees, from various subtropical and midlatitude sources locally 4/17-20. Low odds on all these features with surf holding at mostly flat with a few select spots focusing inconsistent small sets off and on through the period.

Into the long range, the blocking ridge holds SE of New Zealand, so no end in sight to the below average conditions for southerly swell.

In the northern hemisphere, models show the zonal pattern of 4/16-19 giving way to a sharp meridional pattern 4/20-22. It places a large cyclonic jet level gyre south of the Aleutians just west of the dateline, that should have a severe gale to storm force low cell at the surface. With the head of those winds about 1800 nm late Sunday, that should bring in forerunners late Wednesday 4/23, and chances for marginally high surf from 305-320 degrees on Thursday 4/24.

The broad jet level ridge and associated strong surface high pressure area 4/20-22 north of Hawaii should make for a fresh to strong trade wind event and above average, rough, E to ENE windswell locally during this time span.

Long range forecasts are subject to major revisions.

This collaborative forecast will resume on Friday, April 18.

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.

NWS Forecaster and Pat Caldwell, Pacific/Hawaii Liaison Office, NCDDC

Additional Resources:

Waimea Buoy Kailua Buoy Lanai Buoy Barbers Point #2 Pauwela, Maui Hilo Bay Buoy Kaneohe Bay Buoy Hanalei Kauai Buoy Kilo Nalu
Buoy 51001 Buoy 51101 Buoy 51000 Buoy 51100 Buoy 51002 Buoy 51003 Buoy 51004

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