FZHW52 PHFO SRFHFOSURF ZONE FORECASTNATIONAL WEATHER SERVICE HONOLULU HI400 PM HST SUN APR 26 2015OA...

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FZHW52 PHFO
SRFHFO
SURF ZONE FORECAST
NATIONAL WEATHER SERVICE HONOLULU HI
400 PM HST SUN APR 26 2015
OAHU-
400 PM HST SUN APR 26 2015
HIGH SURF ADVISORY FROM 6 AM MONDAY TO 6 PM TUESDAY FOR NORTH
AND EAST FACING SHORES
Surf along north facing shores will be 2 to 4 feet through this evening, then rise gradually to 10 to
15 feet Monday afternoon.
Surf along east facing shores will be 2 to 4 feet through this evening, then rise gradually to 6 to 9
feet Monday afternoon.
Surf along west facing shores will be 1 to 3 feet through this evening, then rise gradually to 6 to 9
feet Monday afternoon.
Surf along south facing shores will be 2 to 4 feet through Monday.
Outlook through Saturday May 2: the new short period north swell will lower gradually Tuesday
night and Wednesday. Strengthening trade winds will cause short period choppy surf to continue
along east facing shores through most of next week. There will also be a series of small south swells
throughout the forecast period.
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

2. encounter rip currents in or near any surf zone.
FXHW52 PHFO
SRDHFO
COLLABORATIVE NEARSHORE SWELL AND WIND FORECAST FOR OAHU
NWS/NCDDC HONOLULU HI
300 PM HST FRI APR 24 2015
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

3. DIR
SPD
TEND
1PM
04/24
2
WNW
11
2
3
UP
13-19
ESE
SAME
7
E
9
6
8
SAME
3
S
14
4
7
DOWN

4. SAT
04/25
2
WNW
10
2
3
SAME
LOW
7-10
SE
DOWN
5
E
9
4
6
DOWN
MED
3
S
13
3
5
DOWN
MED

5. SUN
04/26
2
WNW
9
1
3
DOWN
LOW
7-10
VRB
SAME
2
NNW
16
3
5
UP
LOW
3
E
9
3
4
DOWN
LOW

6. 2
S
12
2
3
SAME
LOW
MON
04/27
8
NNW
12
10
14
UP
LOW
18-22
NE
UP
7
NE
6
2
4
UP
LOW

7. 2
S
12
2
3
SAME
LOW
TUE
04/28
6
N
10
6
10
DOWN
LOW
19-23
ENE
UP
9
NE
8
6
8
UP
LOW

8. 2
S
12
2
3
SAME
LOW
WED
04/29
3
NNE
10
3
5
DOWN
LOW
19-23
E
SAME
9
ENE
8
6
8
UP
LOW

9. 2
S
12
2
3
SAME
LOW
LEGEND:
SWL HGT
OPEN OCEAN SWELL HEIGHT MEASURED FROM TROUGH TO CREST IN FEET LOCATED 20
NAUTICAL MILES OFFSHORE
DMNT DIR
DOMINANT DIRECTION TYPICALLY +/-10 DEGREES IN 16 COMPASS POINTS
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 SURF ZONE
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 LOCATED 20 NAUTICAL MILES OFFSHORE
WIND DIR

10. WIND DIRECTION IN 16 COMPASS POINTS
SPD TEND
WIND 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: 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.

11. 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.

12. 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.
NWS and Pat Caldwell, Pacific/Hawaii Liaison Office, NCDDC
Additional Resources:
Latest North Pacific Surface Analysis
Upcoming tides for select Hawaii locations
Tides for Honolulu
Tide tables for Hawaii
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