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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 1/3rd 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,

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’). H1/100th
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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