PAT CALDWELL

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SwellCaldWell Updated 3 PM Monday, December 5, 2022

DATE	SWELL HGT	SWELL DIR	SWELL PER	SURF H1/3	SURF H1/10	TREND	PROB	WIND SPD	WIND DIR	TREND
1 PM	3	NNE	11	4	6	DOWN		4-8	SE	UP
12/05	3	NNW	10	3	5	DOWN
TUE	3	NNE	14	4	6	UP	MED	9-13	SE	UP
12/06	8	NNW	12	10	14	UP	LOW
WED	3	NNE	13	4	6	DOWN	LOW	19-23	E	UP
12/07	8	NNW	12	10	14	DOWN	LOW
	8	E	7	4	6	UP	LOW
THU	3	NNW	10	4	6	DOWN	LOW	22-27	E	UP
12/08	2	NNW	16	3	5	UP	LOW
	10	E	9	6	8	UP	LOW
FRI	3	NNW	15	4	6	DOWN	LOW	22-27	E	SAME
12/09	10	E	10	7	10	SAME	LOW
SAT	10	E	10	7	10	SAME	LOW	22-27	E	SAME
12/10	1	SSW	15	1	2	UP	LOW

Table Definitions given after Discussion

Summary

Country midweek NNW with E side building midweek and holding elevated into weekend.

Discussion.

Midday Monday 12/05 on northern shores has breakers from 310-030 degrees of 8-11s intervals below the seasonal average under gentle SE breezes. Heights are expected to ramp up above average by midday Tuesday from 320-360 degrees.

On this day, 12/05, in the historical H1/10 visual surf observation Goddard-Caldwell database (starting 9/1968) for the north shore of Oahu, the average is 7 Hs, (14’ peak face, Oahu Surf Climatology) and the largest surf on this date was 20 Hs (sets 40’ peak face top spots) in 2021 from NNW under 15 knot S wind.

Surf arriving 12/5 are the last hurrah stages a declining NNE to NE event and a WNW to NNW event (tail end of last week’s WNW event). Another combo of NNE and NNW due on Tuesday.

The new NNE to NE event (030-050 degrees) is due late Monday. It was generated by a large area of low pressure off the NW USA 12/2-3. Seas were under 25 feet and the head of the fetch was over 1800 nm away—only small surf expected. It should build Tuesday and drop Wednesday.

The new NNW expected on Tuesday has both a remote and nearby source. The remote source was a fast-moving, severe-gale, low-pressure system that tracked east along the Aleutians and strengthened as it approached the Date Line late Saturday. The fetch was short-lived, less than a day over the 320-340 degree band in an area beyond 1500 nm away. Low, longer-period swell from this source should pick up Tuesday PM and drop Wednesday. The nearby source will overwhelm it.

Give the European model the ribbon for best job on forecasting the unfolding low-pressure pattern to the immediate NNW of Hawaii 12/5. Major flip-flopping in location NNW to NNE of Hawaii in the models by the GFS and NAVGEM models last week with both finally lining up with the Euro Sunday into Monday.

The new unfolding pattern has formed a surface low near 30N, 165W. Models show the low center jogging south into Tuesday morning then west away from away from Hawaii 12/7-9. As it was forming late Sunday, a long, wide fetch of near gales, with pockets of gales aimed at targets just west of Kauai. There was some direct aim at the main Hawaii island chain 12/4 PM into 12/5 in an area north of 40N, or 1200 nm away. This portion, plus energy from angular spreading, should raise surf quickly late morning Tuesday above average from 330-360 degrees. It should peak overnight Tuesday and steadily fall on Wednesday. It should fade on Thursday.

A gale low pressure pattern in the western to central Bering Sea set up a long, narrow fetch hugging the south-side of the Aleutians from Kamchatka to the Date Line 12/5-6, aiming highest at targets NE of Hawaii. This could give a short-lived, long-period bump from 315-330 degrees building Thursday and dropping Friday.

Midday Monday 12/05 east side has small, short-period bump from the trade wind belt (50-90 degrees), with dominant surf for NE to N exposures. The latter exposures should top the heights on Tuesday from a NEPAC low (described above).

Looks like wind-heads may win the lottery this week. As the surface low to the immediate WNW to NNW of Hawaii moves west 12/6-7, a strong surface high pressure cell is modelled to set up to the N to NE of the islands. Trades should pick up Wednesday to at least fresh, and into the strong bracket by Thursday. It should hold into the weekend. Breakers from wind swell out of 70-90 degrees should climb above average Wednesday and stay elevated into the weekend under rough chop.

Midday Monday 12/05 on southern shores has the seasonal near nil situation. More of the same is expected on Tuesday.

On this day, 12/05, in the historical H1/10 visual surf observation Goddard-Caldwell database (starting 1972) for the south shore of Oahu, the average is 1.5 Hs, (~3’ peak face) and the largest surf on this date was 5 Hs (10’ peak face) in 2007 from WSW under 20 knot SW winds—kona wind swell.

The building east trade wind swell this week is expected to top the heights for select exposures on the south shore. Otherwise, a pinch of long-period surf from 190-200 degrees is possible Saturday 12/10. The source was a narrow fetch of gales east of New Zealand 12/2-3.

Into the long range, let’s see what Wooly Worm is up to. Someone is sawing some serious Z’s in the back room—yep, it’s Wooly, the weekend party warrior worm. Ah oh, that is not a good clue. Surf likely still sleepy 12/11-14 locally. Wooly’s finally getting up, nice pajamas, I like those tumble weeds and cactus prints. Maybe that’s a hint for more W-component swell (NW to NNW) locally within 12/15-20.

The next SwellCaldWell forecast will be issued Monday, December 12.

Climatology update (Nov 4, 2022) to include through October 2022: (see links to data/stats in Climate Fun 1 below):

Summary (click below for details of each)

South shore, month of OCTOBER 2022: Above average in counts of days in the “3” and “4” Hs heights– 2022 continues to be a banner south swell season.

North shore, month of OCTOBER 2022: After sleepy SEP 2022, north side finally got rolling with above average counts of days in the HIGH category (within 8-12 Hs). And first 3 weeks with light winds, heaps of epic sessions.

Wind-heads: OCTOBER 2022: Trades kicked in last week of Oct to bring number of days of fresh+ trades equal to the long term average (7 days).

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, 1968-2022; (September to June): nmstat09_06

South Shore Oahu, 1972-2021 (March to November): smstat03_11

South Shore Oahu, 1972-2022; (March to October): smstat03_10

Climate Fun 2.

Climate Tidbit- How does N Shore fair under moderate La Nina

*yep, as of August 2021, NOAA suggesting another La Nina winter ahead for 2021-22 season.

LA NINA MODERATE (LM) — SEPTEMBER TO MAY — 1968/69 – 2019/20

Note:

1) Year denotes year of start of season Sep-May,

eg., 1968 refers to Sep 1968 – May 1969

2) Height in Hawaii scale, H1/10th, upper end of range, Goddard-Caldwell Database

3) Climate Signal (CS):

E:El Nino, L:La Nina, S:strong, M:moderate, W:weak,

N: Neutral, (+:leans El Nino, -:leans La Nina)

Count of Days Per Season of Surf by Size Category

Year CS 3-4 5-7 8-12 13-19 20+ 8+ (size category, Hawaii scale)

1970 LM 84 101 39 5 4 48 (ie, 84 days in 1970-71 were 3-4 Hs, etc.)

1975 LM 96 77 47 11 1 59

1998 LM 89 74 52 16 6 74

1999 LM 72 79 47 16 1 64

2007 LM 74 75 51 17 3 71

2011 LM 88 58 39 13 3 55

2017 LM 104 54 46 7 3 56

Average 86.7 74.0 45.9 12.1 3.0 61.0 La Nina Moderate Sep-May

Average 86.2 71.5 51.7 16.5 4.5 72.6 All years Sep-May

So, yes, it shows moderate La Nina years have less than average in larger wave size categories (though 1998-99 closer to normal and above average giant)– Ma Nature hates to be boxed in– keeps you guessing.

*Update June 4 to include Sep-May 2020/21 season surf observations: How many days in each size category?

Year CS 3-4 5-7 8-12 13-19 20+ 8+ (Hawaii scale)

2020/21 LM 104 53 39 14 2 55 this season Sep to May

Average 87 71 51 16 4 71 All years (Sep-May)

Yep, historic surf obs say La Nina moderate is below average, and 2020/21 (La Nina Moderate) fit the expected slacker count in category of days per season of high+ (8 Hs plus) than the average over all years (seasons 1968/69 through 2019/20).

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 1/3^rd 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’). H1/100^th 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.