PAT CALDWELL

Hazards

HIGH SURF ADVISORY FOR SOUTH FACING SHORES

Forecast

Surf along north facing shores will be 4 to 7 feet through Saturday. Surf along west facing shores will be 3 to 6 feet tonight, rising to 5 to 8 feet Saturday. Exposures that face south will see significantly larger sets on Saturday. Surf along south facing shores will be 4 to 8 feet tonight, rising to 8 to 12 feet Saturday. Surf along east facing shores will be 2 to 4 feet through Saturday.

Outlook

Outlook through Friday October 26: A large, long period south swell will build tonight, peak through the weekend, and gradually diminish early next week. A slightly smaller long period south swell is expected Wednesday through Friday, keeping surf elevated along south facing shores. A short period north- northwest swell will gradually diminish over the weekend. A moderate northwest swell is possible Tuesday through Thursday. No other significant swells are expected. Surf heights are forecast heights of the face, or front, of waves. The surf forecast is based on the significant wave height, the average height of the one third largest waves, at the locations of the largest breakers. Some waves may be more than twice as high as the significant wave height. Expect to encounter rip currents in or near any surf zone.

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About Collaborative Surf

This collaborative forecast will be updated Monday through Friday at 300 PM when Pat Caldwell is available.

Collaborative Surf Table

FORECAST
DATE
SWL
HGT
DMNT
DIR
DMNT
PD
H
1/3
H
1/10
HGT
TEND

PROB
WIND
SPD
WIND
DIR
SPD
TEND
1PM
10/19
3NNW1146UP7-10ENEDOWN
2SSW1735UP
SAT
10/20
5N1057SAMEMED9-13NEUP
5SSW181014UPMED
SUN
10/21
4N946DOWNLOW9-13ENEUP
5SSW171014SAMEMED
MON
10/22
2NNW1124SAMELOW11-16ENEUP
5SSW15812DOWNMED
TUE
10/23
3NNW1346UPLOW13-19ENEUP
5ENE724UPLOW
4S1469DOWNLOW
WED
10/24
3NNW1246SAMELOW13-19ENESAME
6ENE734UPLOW
4S1358DOWNLOW
2SSW1846UPLOW

Collaborative Surf Table Legend

LEGEND:

SWL HGTOpen ocean swell height measured from trough to crestin feet located 20 nautical miles offshore
DMNT DIRDominant direction typically +/-10 degrees in 16 compasspoints
DMNT PDDominant period in seconds
H1/3Significant wave height in the surf zone
H1/10Average height in the highest one-tenth waves in the surfzone
HGT TENDHeight tendency of swell (valid values: UP/DOWN/SAME)
PROBProbability of occurrence (valid values: HIGH/MED/LOW)
WIND SPDOpen water wind speed measured in knots located20 nautical miles offshore
WIND DIRWind direction in 16 compass points
SPD TENDWind speed tendency (valid values: UP/DOWN/SAME)

Disclaimer

Surf heights will vary between different beaches and at the same beach at different break areas.

Collaborative Surf Discussion

DISCUSSION: SUMMARY:. Below average north side and above average from the south. DETAILED:. Mid Friday on has short-period breakers from 325-350 degrees at levels below the October average. Surf should nose a notch under the average on Saturday. The large Aleutian low pressure system 10/13-15 that produced the above average surf locally 10/16-18 weakened to near gales south of the Aleutians over a large area 10/16-17. This is the source for the below-average surf 10/19 in the morning. This low energy from 325-350 degrees should hold into Sunday with a downward trend as another short-period event overrides it. A compact low pressure tracked east along 40N 10/17-18 with strong to near gale winds over a short fetch to near 30N north of Hawaii. The NOAA NW Hawaii buoys picked up 8-12s energy from NNW to N after 1 AM HST 10/19. The PacIOOS/CDIP Hanalei, Kauai buoy late morning 10/19 jumped from this source. It should fill into Oahu 10/19 PM. This event should hold into Sunday from 340-010 degrees at levels below the October average. The jet stream is modelled to become zonal, or west-to-east, over the weekend across the central north Pacific and hold into mid next week. Such patterns typically mean below average surf in Hawaii. Another compact low pressure further away 10/18-19 to the NNW of Hawaii is moving NE and strengthening once out of the Hawaii swell window. It could make for tiny to small breakers 10/22 from 325-345 degrees. A stronger low pressure system near 170E in the Bering Sea has marginal gales hugging the Aleutians 10/18-19. It is modelled to move steadily east under the zonal jet stream. A small event is predicted locally, picking up 10/23 PM and dropping 10/24 from 320-340 degrees. Mid Friday on has minimal surf from 45-90 degrees. Low surf from this direction should continue on Saturday. More northern exposures should have surf aforementioned. See the latest NWS State Forecast Discussion regarding the local winds and skies. The trade wind pattern for 10/20-22 is expected to have a short fetch E to NE of Oahu thus the wind waves would lean to the chop end of the spectrum and not long enough wave periods to make breakers beyond tiny. The fetch and local winds are predicted to trend up 10/22-24 with a subsequent uptick expected in breakers from wind waves out of 50-90 degrees. Mid Friday on has rising breakers from 190-220 degrees at levels near the summer south swell average. An increase is predicted for Saturday. The NOAA offshore southern buoys showed a peak in the 16-17 band overnight into early 10/19 and the PacIOOS/CDIP nearshore southern buoys show a rise in the same wave period band mid morning. This event was generate by gales in the Tasman Sea west of New Zealand and a narrow fetch of gales east of New Zealand 10/11-12. This event will be overridden by a larger event on Saturday. A severe-gale to storm-force system moved from S of New Zealand 10/12 to SE of New Zealand 10/13 with a large area of seas growing above 30 feet. The associated low pressure center moved steadily east along 65S the slowed in pace as it settled near 150W 10/15. A fetch of over 1500 nm long and 1000 nm wide formed between the broad area of low pressure south of French Polynesia and a strong surface high pressure over the Tasman Sea. The strongest winds were during the onset 10/12-13 though gales to severe gales held on 10/14-16 over the 175-200 degree band with the head of the fetch to near 3500 nm away. Such a large source means a long- lived, well-above average event. The NOAA southern buoy 51002 showed a sharp jump in the 19-21 second energy late morning 10/19. The event should begin to fill in near sundown and slowly build above average by Saturday morning. The event should continue to rise into 10/20 PM from 185-200 degrees. The event should peak within late Saturday to mid Sunday. The wave direction should spread within 175-200 degrees by 10/22 as the heights slowly drop yet remain above average into 10/24. Another severe-gale to storm-force system took a similar track SE of New Zealand 10/17-18 and is expected to occlude near 150W 10/20. It also has been building a massive wave generation region aimed at Hawaii. Long-period forerunners from this source should be building 10/24 from 185-200 degrees. , the new pulse should peak well above average 10/25 from 185-200 degrees. It should remain elevated into 10/27 from 175-190 degrees then slowly drop to near average levels from 160-180 degrees 10/29. In the northern hemisphere, models suggest below average surf to hold from NNW to N 10/25-27. East side should pick up to near average 10/25-26 from 50-90 degrees. Long range forecasts are subject to low confidence. This collaborative forecast will resume on Monday, October 22. This forecast was produced through the collaborative efforts of NWS and NCEI. Please send suggestions to w-hfo.webmaster@noaa.gov or call the Warning Coordination Meteorologist at 808-973-5275. ADDITIONAL RESOURCES: See http://www.prh.noaa.gov/hnl/pages/marine.php

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NWS Forecaster and NCEI Pat Caldwell

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