PAT CALDWELL

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SwellCaldWell Updated 3 PM Monday, March 18, 2024

DATE

SWELL

HGT

SWELL

DIR

SWELL

PER

SURF

H1/3

SURF

H1/10

TREND

PROB

WIND

SPD

WIND

DIR

TREND

12 PM

5

WNW

17

8

12

DOWN

5-10

ENE

SAME

03/18

1.5

SSW

17

3

6

SAME

 

 

 

 

TUE

4

NW

12

6

8

DOWN

MED

9-14

ENE

UP

03/19

1.5

SSW

15

3

5

DOWN

LOW

 

 

 

 

3

WNW

19

6

8

UP

LOW

 

 

 

WED

6.5

WNW

16

10

14

UP

LOW

10-15

ENE

UP

03/20

1.4

SSW

14

2

4

DOWN

LOW

 

 

 

THU

5

NW

14

6

10

DOWN

LOW

11-16

NE

UP

03/21

5

ENE

6

1

2

UP

LOW

 

 

 

 

1.2

SSW

12

1

3

DOWN

LOW

 

 

 

FRI

3

NNW

11

4

6

DOWN

LOW

13-19

NE

UP

03/22

6

ENE

6

2

3

UP

LOW

SAT

3

WNW

18

5

7

UP

LOW

18-22

ENE

UP

03/23

8

ENE

7

3

5

UP

LOW

 

 

 


Table Definitions given after Discussion

Summary

First day of spring arrives Tuesday, aloha winter, we’re going to miss you. Above average N shore midweek.  Fresh to strong trades and building wind swell late in the week. SSW swell lingering
into midweek.

Discussion

Midday Monday 03/18 on northern shores has declining breakers near the seasonal average from 305-315 degrees of 14-20s periods under gentle trade winds. Heights should fall to moderate levels on Tuesday with a new, long-period, WNW building late in the day.

 

On this day, 03/18, in the historical H1/10 visual surf observation Goddard-Caldwell database (starting 9/1968) for the north shore of Oahu, the average is 7.0 Hs, (14’ peak face, Oahu Surf Climatology) and the largest surf on this date was 20 Hs (sets 40’ peak face top spots) in 2019 from NNW under 15 knot NE winds.

 

Moon’s view

  • Series of lows coming off Asia spaced a few days apart last week into this week to winter-caliber strength, keeping the winter vibration in the Hawaiian surf.

Winter-caliber, NWPAC source 03/12-14—a Kuril hugger source on decline 03/18

  • Backstory:
    • A hurricane-force low deepened to 955 mb east of the Kuril Islands by early 03/13. The system was broad, with a wide long fetch over the 305-315 degree band 03/13-14 maintaining extreme winds. Seas grew over 35’ over a large area beyond 2300 nm away. The center stayed close to the Kuril Islands throughout.
  • Pulse status:
    • NOAA NW Hawaii buoy 51001 midday 03/18 has the dominant period down to 14s as energy levels slowly wane over the 12-16s band.
    • PacIOOS/CDIP Waimea, Oahu buoy showed top readings near sundown Sunday 03/17 to the wee hours Monday 03/18. Deep water swell heights and dominant wave period are slowly shifting down into midday.
  • Prognosis:
    • Given the remote source, it takes time for the swell trains to unravel as the dominant wave period shifts down. This should ensure at least some moderate sets for Tuesday morning with a steady decline from 305-315 degrees.

NWPAC to Date Line source 03/15-18

  • The next surface low formed 03/15 east of Japan. It tracked east near 40N, reaching about 2100 nm away (40N, 170E) with severe gales to storm-force winds 03/16 PM HST. Winds were strongest at this stage. The long-period energy from 300-310 degrees should be on the rise locally mid-afternoon Tuesday as heights slowly climb.
  • The low center tracked ENE as it weakened 03/17, reaching the Date Line overnight. Seas were up to 30’ west of the Date Line, but mostly 20-25’ once in the western hemisphere. Models show it shifting N and fading 03/19-20.
  • Surf should climb above average overnight Tuesday night. Peak of the swell is expected near noon on Wednesday from 305-320 degrees. Heights should remain moderate on Thursday morning from 310-330 degrees, then fall into the small bracket on Friday from the same direction.

Another Kuril hugger source 03/18-20

  • The next low is east of Hokkaido 03/18. Models deepen the center to 976 mb on Tuesday with storm-force winds within 2400-2800 nm away. It weakens steadily on 3/20.
  • This source is expected smaller in size and strength than the event that peaked locally Sunday night 03/17.
  • It should have long-period onset Saturday, peak overnight likely below average from 300-310 degrees, and hold moderate through Sunday from the same direction.

Midday Monday 03/18 on eastern shores has breakers near an east side minimum. Heights should remain low on Tuesday.

Windward wind-head concerns —

  • Surface high increasing through the week N of Hawaii, but Tuesday into Wednesday has some potential wind suppression from a nearby upper-level low. Better overhead stability going into the weekend, which should allow the pressure gradient across the islands to tighten. This would draw up some fresh breezes by late Thursday with a slow increase into the weekend.

East side surfer interests—

  • Fetch too short and too weak early on this week, but a trend up Thursday into Saturday to near average for the weekend from 50-90 degrees.

 

Midday Monday 03/18 on southern shores has long-period swell from 185-200 degrees of 14-20s intervals with breakers near the seasonal average. Heights should hold about the same to a notch less on Tuesday (for the active spells at least, like any south swell—long lulls).

 

On this day, 03/18, in the historical H1/10 visual surf observation Goddard-Caldwell database (starting 1972) for the south shore of Oahu, the average is 1.7 Hs, (~3’ peak face) and the largest surf on this date was 4 Hs (8’ peak face) in 1995 from S under LV winds, sweet.

 

Moon’s view:

Pair of austral, midlatitude sources overlapping locally 03/18

Marginal source E of New Zealand 03/08-09

  • This compact gale had a favorable track for Hawaii surf potential tracking to near 3800 nm away, though the magnitude was meek. Wave periods shorter, so travelled slower, allowing the following to catch up. It is likely in the mix 03/18, but should fade Tuesday.

Large, short-lived source S to SE NZ 03/10-11

  • This low had severe gale to hurricane-force winds over a sizable area with 55-65S (~5000 nm away) with seas growing over 35’. Aim was highest toward the Americas.
  • PacIOOS/CDIP American Samoa buoy is not operating. No Pulse status. NOAA southern buoy 51002 (south of Oahu, best indicator) is still inoperable. Local buoys overwhelmed by the large WNW energy. The eyes have it for pulse status.
  • It filled in locally Sunday PM. Some spells pinch overhead Monday morning, wahoo, scored some nice ones, but some stinkin’ long lulls too, surfboard blues).
  • Likely peaking 03/18. With the remote, large source, it ought to linger through Wednesday.

 

Into the long range, let’s see what Wooly Worm is up. Wooly’s in the kitchen listening to Irish music. What’s that he’s making, green something—keeping that St. Paddy’s day theme going. Oh, it’s wasabi piled on ahi rolled with lettuce into a wrap. Wasabi, must be the clue—more swell from Japan on the menu. Models show another winter-caliber low forming east of Tokyo 03/20 with a track towards the central Aleutians by 03/23. A new, long-period, WNW event is due Monday 03/25 to near average, holding moderate 03/26 and small 03/27 from 300-320 degrees.

 

The next SwellCaldWell forecast will be issued Wednesday, March 20.

Climatology update (March 4, 2024) to include through February 2024: 

Summary (click below for details of each)

South shore, month of February 2024:  Tail end of long-lived west on Feb 1; otherwise, slim pickens, ssstat02.

 

North shore, month of February 2024:  Near average for counts of days in the big stuff ( High, XL, and Giant brackets),  nsstat02.  Bad timing on winds for some of those biggest days.   For the 2023-24 season so far (Sep-Feb), hovering near average most categories, but below for Giant, nmstat09_02Just like the disappointment for the 2023 south swell season with El Nino brewing, the winter got short-changed as well.  Not every El Nino is alike, Ma Nature is a complicated lady with many moods.

Wind-heads: February 2024:  Handful of fresh to strong N wind days, and oodles of fresh to strong trade wind days, wwstat02.  It is common for above average trades as the El Nino pattern begins to transition towards neutral.  Actually it is exactly that, the return of normal to above average trades in the tropical and equatorial Pacific is one of the primary mechanisms of whittling down an El Nino.


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, 1968/69-2022/23; (full season, September to June)nmstat09_06

North Shore Oahu, 1968/69 to 2023/24 (Sept – Jan): nmstat09_02

South Shore Oahu, 1972-2023 (March thru Nov): 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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