PAT CALDWELL

SwellCaldWell Update 3 PM Wednesday, February 24, 2021

DATE	SWELL HGT	SWELL DIR	SWELL PER	SURF H1/3	SURF H1/10	TREND	PROB	WIND SPD	WIND DIR	TREND
3 PM	3	NW	14	4	6	DOWN		20-25	E	SAME
02/24	11	ENE	10	8	10	UP
THU	2	NNW	12	2	4	DOWN	LOW	22-27	E	UP
02/25	3	NW	18	5	7	UP	LOW
	12	ENE	10	9	11	UP	LOW
FRI	3	NNW	14	4	6	DOWN	LOW	22-27	E	SAME
02/26	13	ENE	10	10	12	UP	LOW
	1.5	SSW	17	3	4	UP	LOW
SAT	2	NNW	12	2	4	DOWN	LOW	18-22	E	DOWN
02/27	2	NW	18	4	6	UP	LOW
	10	ENE	11	8	10	DOWN	LOW
	1.5	SSW	15	3	4	SAME	LOW
SUN	4	NNW	14	6	8	DOWN	LOW	19-23	ENE	UP
02/28	10	ENE	11	8	10	UP	LOW
	1.5	SSW	14	2	4	DOWN	LOW
MON	3	NNW	12	4	6	DOWN	LOW	22-27	ENE	SAME
03/01	12	ENE	10	9	11	SAME	LOW
	1	S	13	2	4	DOWN	LOW

Table Definitions given after Discussion

Summary

NW to NNW swells hold steady but below average, while east side tops the heights
under rough conditions.

Discussion

Midday Wednesday 2/24 on NW to N exposures has surf from 305-325 degrees below the seasonal (Sep-May) north shore average. This event is trending down into Thursday morning with a new event filling in Thursday midday.

On this day, 2/24, in the historical H1/10 visual surf observation Goddard-Caldwell database (starting 9/1968) for the north shore of Oahu, the average is 6.5 Hs, (~13’ peak face) and the largest surf on this date was 20 Hs (~40’ peak face outer reef top spots) in 1986 (most recent year if tied). Wave direction and local wind unconfirmed. February 1986 had an exceptionally active spell of days at extra-large (5 days vs average of 3) and giant (7 days vs average of 1).

A broad ridge at jet level over the central N to NE Pacific has set up a block, keeping low pressure systems west of the Date Line. Winter-caliber storms have been forming over the low-pressure breeding grounds east of Japan, but the track to the NE has kept the head of the fetches further from Hawaii. In turn, Hawaii is experiencing below seasonal average surf. The spacing between new born lows has been about 2-3 days, so at least these remote, overlapping events are not allowing the north shores to go full July mode.

A new low in the series established a ribbon of severe gales Sunday 2/21 centered from 315 degrees stretching east about 800 nm from the Kuril Islands. The head of the fetch was about 2400 nm. With 17 second wave energy traveling about 600 nm per day, and counting from Sunday PM, brings the energy in locally Thursday PM. Longer period energy of 18-20 seconds should fill in late morning to midday, with the 17 second energy in near sundown into the night bringing surf a pinch overhead. This event from 305-325 degrees should peak Friday night, then slowly drop into Saturday.

The next new low in the series was a doppelganger of the aforementioned low in track and breadth, though it was a notch stronger—to storm force. It formed 2/23 and is holding strong 2/24. Models show it weakening 2/25. This remote source could give a pinch more size to the local surf. It should slowly fill in Saturday PM from 305-320 degrees, peak Sunday near dawn, then slowly drop into Monday from 305-325 degrees.

Kailua, Oahu kite reconnaissance Monday (11m full power), Tuesday (11m depowered), and Wednesday (9m full powered) within about 10 AM to noon found each day with winds progressively stronger and breaker size bigger. Thursday is expected to continue the upward trend for winds and waves.

The La Nina pattern is locked in with a massive area of surface high pressure over the N to NE Pacific. The fetch of wind swell aimed at Hawaii stretches all the way to California, with more NE direction further out, ENE direction midway, and E direction to the wind swell closest to Hawaii, which is dominant. More of the same through the period with rough, well above average breakers from 40-90 degrees.

An upper-level trough and its surface low-pressure reflection about 600 nm WNW of Oahu 2/22-24 has given the local trades much more east component than normal, ranging within 80-100 degrees. A new high pressure is moving east from the Date Line 2/24, and looks like the Surf Pickle (that sand in a panty hose surfboard wax remover thingamajig) as it squeezes up around the aforementioned trough. By Thursday, this new high is expected to become established NNE of Hawaii, with most models showing a maximum to this week’s wind speeds locally and just upstream for Thursday into Friday 2/25-26. This should turn up the breaker size another notch.

Models hint of another Surf Pickle moment with a new high moving east from Date Line Saturday, coinciding with a slight drop in local trades, though still fresh to strong, but then increasing Sunday into Monday as the new high gets established NNE of Hawaii. More strong breezes, hold on to your pickle.

Mid Wednesday 2/24 on southern shores has breakers at a seasonal minimum. Aforementioned trade wind swell has a lot of east direction and is affecting select south shore reefs through refraction and diffraction. This should be the dominant surf through the period.

A broad area of low pressure to the SE of New Zealand 2/18 moved east along 55S. It was strongest to severe gales and seas to 30 feet 2/18. The winds favored lower-end gales 2/19, though the source region expanded over the 175-195 degree band to the SW to S of French Polynesia, south of 35S.

Long period forerunners of 18-22 seconds have hit the PacIOOS/CDIP American Samoa buoy 2/22, and 14-16 seconds 2/23. Wave energy stayed low, but likely enough to give a bump locally. Given the above average E wind swell this week into early next week, there will at least be some breakers all weekend with the combined sources.

Into the long range, looks like slumber down under over recent days and into the long range. No S swells expected anytime soon for early March.

The real question is what’s Wooly Worm up to today. His cousin from Austria, Wormold, is still in the backyard by the weight lifting set, but he tweaked a tendon, when he challenged Wooly’s girlfriend, Wormina, to a lifting contest. She may look lean, but she’s got some major strength. Wormina is smiling and holding the winner’s trophy– she is one strong La Nina. Guess that doesn’t bode well for Wormold’s so-called muscular swell prognosis for midweek next week. Better tone that down to another below average event within 3/3-5 out of NW to NNW. La Nina expected to still reign.

The next SwellCaldWell forecast will be issued Friday, February 26.

Climate Tidbit- How does N Shore fair under moderate La Nina: history vs this year

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.

What about this season (2020-21) Sep-Jan?

Year CS 3-4 5-7 8-12 13-19 20+ 8+

2020 LM 44 36 26 10 2 38 this season starting Sep to date

Average 45 41 31 11 3 45 All years (Sep-Jan)

We are running well below for 8-12 Hs category, but close for the extra-large (13-19 Hs) and giant (20+) categories, thanks to the abundant surf in Dec 2020 to mid January 2021. Wooly my friend, dial us in here, what’s the rest of the winter going to be? I’ll keep an eye on him for clues.

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,
H1/3 to H1/10	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.