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SwellCaldWell Updated 3 PM Monday, February 17, 2025

DATE

SWELL

HGT

SWELL

DIR

SWELL

PER

SURF

H1/3

SURF

H1/10

TREND

PROB

WIND

SPD

WIND

DIR

TREND

1 PM

5

NW

20

10

15

UP

11-16

NNW

UP

02/17

2.5

NNW

10

2

4

DOWN

 

 

 

 

 

2.5

W

9

2

3

DOWN

 

 

 

 

TUE

9

WNW

16

15

20

SAME

LOW

8-12

E

SAME

02/18

 

 

 

WED

8

WNW

15

14

18

DOWN

LOW

8-12

E

SAME

02/19

 

 

 

THU

7

NW

14

10

14

DOWN

LOW

8-12

E

SAME

02/20

 

 

 

FRI

5.5

NW

14

7

11

DOWN

LOW

8-12

E

SAME

02/21

SAT

3.5

NW

13

5

7

DOWN

LOW

5-10

E

DOWN

02/22

 

 

 


Table Definitions given after Discussion

Summary

Active midwinter pattern.

Discussion

Midday Monday 02/17 on northern shores has rising surf above the seasonal average from 310-320 degrees of 16-22s intervals. Heights are predicted to remain elevated on Tuesday.

 

On this day, 02/17, in the historical H1/10 visual surf observation Goddard-Caldwell database (starting 9/1968) for the north shore of Oahu, the average is 8.0 Hs, (16’ peak face, Oahu Surf Climatology) and the largest surf on this date was 35 Hs (sets 70’ peak face top spots) in 1983—middle of a strong El Nino winter.

 

Moon’s view

  • NWPAC to central NPAC winter mode dominated by cyclonic circulation.

 

Kurils low hurricane force low 2/13-16—two parts, 310-320 and 295-310 degrees

  • Backstory:
    • Part 1—310-320 degrees. A low deepened to ~950 mb off the Kurils Thursday 2/13. It occluded right away, coinciding with maximum strength (hurricane force), broadening of the gyre, and stalling of the track.
    • The center was nearly stationary for 3 days into Saturday with the 310-320 degree fetch slowly weakening.
    • Sunday saw the 310-320 degree fetch stretch east to the Date Line, at which point the aim became more west to east—NE of Hawaii. This fetch is fading 2/17.
  • Pulse status:
    • NOAA NW Hawaii buoy 51001 ramped up sharply Sunday night in the 16-21s band. Deep water swell to 10’.
    • PacIOOS/CDIP Hanalei buoy to 7’ swell by 1PM 2/17, while Waimea around 5’. Just goes to show you how much more a swell jacks up upon breaking with the longer period energy. Cams showing above average surf. Sets are inconsistent given the long travel and the sharp focus in the long period bands.
  • Prognosis:
    • The 310-320 degree energy should peak on Tuesday then slowly drop into

 

 

  • Part 2 Kurils system 2/14-16—295-310 degree energy
    • The broad gyre aforementioned began to focus dominant strength over the 295-310 degree band starting Friday 2/14 hugging Japan stretching eastward. Seas grew over 30’
    • A captured fetch was set up with the fetch reaching the Date Line Sunday about 1200 nm away.
    • The pattern weakened sharply 2/17.
      • This more WNW energy should overlap the aforementioned.
      • Some Kauai/Niihau shadow issue down-swell islands.
      • It should be filled in on Tuesday and hold about the same on Wednesday.
      • Slow downward trend into Saturday.

 

Midday Monday 02/17 on the east side has breakers way below the trade wind swell average. Similar surf on Tuesday.

Windward wind-head concerns —

  • Hovering just below the desired threshold this week.

East side surfer interests—

  • Whole lotta nada, Country swells placing east side mostly in shadow.

 

Midday Friday 02/17 on southern shores has tiny to small breakers, highest on W-exposures. More of the same on Tuesday with W-exposures nosing up.

 

On this day, 02/17, in the historical H1/10 visual surf observation Goddard-Caldwell database (starting 1972) for the south shore of Oahu, the average is 1.4 Hs, (~3’ peak face) and the largest surf on this date was 5 Hs (10’ peak face) in 1999 from S under 10 knot E winds— rare winter, above average southern hemi.

 

Moon’s view:

  • Some systems hugging Antarctica SE of New Zealand— low odds.

 

Antarctic low 2/13-15

  • A fetch stretched NE from the ice sheet aiming highest at the Americas with mostly middle gales. There may be some tiny to small breakers locally within 2/21-23 from 180 degrees.

 

Into the long range, let’s see what Wooly Worm is up. Lunch time, I hear lots of noise in the kitchen. There’s Wooly with a big pot of stew. Good sign plenty more winter goodies to come. Models show next WNW/NW rising above average Sunday 2/23 with new events spaced about 3 days apart right out to the end of Feb and start of March.

 

The next SwellCaldWell forecast will be issued Wednesday, February 19.

 

 

Climatology update (February 4, 2025) to include through January 2025: 

Summary (click below for details of each)

North shore, month of January 2025:  Above average for XL days (sub giant) in January, nsstat01 otherwise near to below average.  For the start of the 24/25 season, looking good, above average for Xl to giant, nmstat09_01.

South shore, month of January 2025:  Minimal from southern hemi but near average from west or local konas, ssstat01.

Wind-heads: January 2025:  Fresh+ trades days wayyyyy below average,  wwstat01.  So much for the positive correlation between enhanced fresh trades and La Nina winter months in Hawaii.  Southerly konas average, with post-frontal N-component winds above average.


Climate Fun 1.

Monthly Stats

North Shore Oahu (1968-present):

January: nsstat01

February: nsstat02

March: nsstat03

April: nsstat04

May: nsstat05

June: nsstat06

July: nsstat07

August: nsstat08

September: nsstat09

October: nsstat10

November: nsstat11

December: nsstat12

South Shore Oahu (1972-present):

January:  ssstat01

February: ssstat02

March: ssstat03

April: ssstat04

May: ssstat05

June:ssstat06

July: ssstat07

August: ssstat08

*Picts surf forecaster validation duties Big Wednesday 8/18/21

(photos Shredsniper.com, Mike Carroll)

September: ssstat09

October: ssstat10

November: ssstat11

December: ssstat12

Wind (1988-present, PC’s best guess):

January:  wwstat01

February: wwstat02

March: wwstat03

April: wwstat04

May: wwstat05

June: wwstat06

July: wwstat07

August: wwstat08

September: wwstat09

October: wwstat10

November: wwstat11

December: wwstat12

Seasonal Stats

North Shore Oahu, 1968/69-2023/24; (full season, September to June)nmstat09_06

North Shore Oahu, 2024 new season (Sept-DEC): nmstat09_01

South Shore Oahu, 1972-2024 (March thru November): smstat03_11


 

Helpful links,

Oahu Surf Climatology

Island Shadows

Educational outreach: Waves 101– Why Surf Varies Time/Place

Table Definitions

DATE

Represents daylight hours in zones of high refraction (biggest surf spots
for given incident swell direction, period and height). First row(s) in table
refers to observations from buoys (swell) and cams (breakers) made for the time when
the SwellCaldWell forecast was updated. Other rows
refer to forecast for spell (~30-60 min) within daylight when arrival of
maximum wave energy, or active envelopes, occur. This forecast tends
to bias high for safety (and easier to ride a bigger board if surf is smaller
than expected, than to ride a shorter board when bigger). Even under “steady”
swell, heights vary spell to spell through a day.

SWELL HGT

Deep water swell (H1/3) height (feet) corresponding to a nominal (~3 mile) location
offshore of Oahu seaward of the coastal shelf for the given incident swell
direction. Deep water swell height
from each unique wave-generating source is obtained by summing up all energy
for wave periods > 10 seconds, which removes the wind swell. H1/3 is the
average of the highest 1/3rd of all waves coming in for the
targeted high energy envelope spell from this defined source. Wind swell are
defined for wave periods <= 10 seconds.

SWELL DIR

Deep water swell direction (from) centered on 16 point compass bands.

SWELL PER

Deep water swell period (seconds).

SURF H1/3

Breaker H1/3 (defined above) height (feet, peak face) during most active envelopes. H1/3
sets arrive about every 3 minutes with large variance.

SURF H1/10

Average of highest 1/10th of all breakers (feet, peak face) during active envelopes;
H1/10 sets arrive about every 10 minutes with large variance.

PEAK FACE

Trough to crest height (feet) on shoreward side of breaker at moment and location along
wave front of maximum cresting,

Ocn H1/100

Cleanup or

Sneaker set

Waves arrive within a range of sizes. Surf zone enthusiasts emphasize the smaller percent
of larger waves when communicating a report in an X to Y occasional Z
format. The X to Y range is nominally
H1/3 to H1/10. The Z, or sneaker or
cleanup sets, are the H1/100, which is about 1.3 times the H1/10 (eg., H1/10=10’ gives H1/100=13’). H1/100th
sets arrive on average every 90 minutes with large variance. Thus your typical
2 hour session is bound to see at least one cleanup set.

TREND

Breaker height (wind speed) tendency during daylight

WIND SPD

Wind speed (knots) for nominal coastal location on the windward side relative to
prevailing large scale wind (ie,
east side under trades or S or W side under konas),

WIND DIR

Wind direction (from) centered on 16 point compass bands. LV refers to light and variable.

 

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