HIC 728   9.15.20 ONLINE+INSTORE

PAT CALDWELL

Hazards

No high surf advisory or warnings.

Forecast

NOTE: Please check with local authorities regarding beach closures.
Surf along north facing shores will be 3 to 5 feet today, lowering to 1 to 3 feet Friday.
Surf along east facing shores will be 2 to 4 feet through Friday.
Surf along south facing shores will be 2 to 4 feet today, rising to 3 to 5 feet Friday.
Surf along west facing shores will be 2 to 3 feet through Friday.

Outlook

Outlook through Thursday September 17: The current small northwest swell will gradually lower today through Friday, with very small or flat surf expected Saturday through the middle of next week.
Surf along south facing shores will hold near the summertime average today through Saturday.
East shore surf is expected to remain small and below the summertime average through the middle of next week.
A persistent small southeast swell will remain in place through the middle of next week, bringing steady small breakers into exposed shorelines.
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.
The SRFHFO product will change format and be expanded to more islands on or about September 10, 2020.
More information at: https://www.
weather.
gov/hfo/statesurf2020 .

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
09/25
5N13810SAME12-18EDOWN
6E623SAME
2SSW1334DOWN
SAT
09/26
4N1158DOWNMED10-14EDOWN
5E612DOWNLOW
3SSW1668UPLOW
1SSW1946UPLOW
SUN
09/27
3N1035DOWNLOW8-12EDOWN
3SSW1868SAMELOW
MON
09/28
4E924UPLOW7-10ENESAME
2SSW1546DOWNLOW
TUE
09/29
3NNW1146UPLOW7-10NESAME
6E935UPLOW
2S1334DOWNLOW
WED
09/30
4NNW1468UPLOW7-10ESAME
4E924DOWNLOW
2S1123SAMELOW

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 Links

Compass & Swell Shadow Lines for Hawaii

Oahu Surf Climatology

Disclaimer

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

Collaborative Surf Discussion

DISCUSSION: SUMMARY.
.
.
.
Last week of September in seasonal transition mode with surf from around the compass.
DETAILED:.
Mid Friday on breakers from 345-360 degrees above the September average.
Heights are predicted to trend down over the weekend from the same direction.
This first overhead swell of the fall 2020 season was generated by an occluded low-pressure system in the Gulf of Alaska 9/21-23.
Highest seas were aimed NE of Hawaii.
NOAA buoy 51000 NE of Hilo was much higher than 51001 NW of Kauai through the event 9/24-25.
The midday 9/25 51000 readings still show active swell.
Surf is expected to hold above the September average into Saturday then fall below average Sunday from 345-010 degrees.
The tail of the fetch of near gales was near the eastern Aleutians into early 9/23, placing the end of the event by late Sunday or early Monday with small breakers.
A long-wave jet stream pattern is expected to form 9/27 with axis near the longitudes of Hawaii with several reinforcement short-waves from the NW to keep it active into 10/3.
At the surface, a complex, broad, low-pressure pattern with a series of low centers are modelled to unfold NNW to N of Hawaii this weekend and holding much of next week.
This should equate to an active NNW to N surf pattern locally under gentle breezes 9/29-10/3.
The first fetch of the new complex low-pressure pattern is due to set up Saturday with strong to near gale winds about 1200 nm away over the 330-340 degree band.
This should bring up surf near the September average on Tuesday.
The low center associated with the first fetch is modelled to track NE toward the Aleutians and gain gale status 9/26-27.
At the same time, another near gale low is modelled to form NNW of Hawaii near 40N, 160W, pushing a fetch within 1000 nm 9/28.
Stay tuned for specifics, with both of the sources suggested to trend surf up 9/30 from within 320-360 degrees near the October average.
Mid Friday on has breakers from 60-90 degrees below the trade wind swell average.
Heights are predicted to decrease on Saturday with northerly exposures topping the height, aforementioned.
Remnant of tropical system Lowell is modelled to steadily track towards Hawaii along 20N 9/25-29 with a slow weakening trend.
High pressure north of the remnant should allow enhanced trades to strong levels with pockets of near gales.
This should result in a remote-source wind swell.
It is due to build Monday 9/28 from 70-90 degrees, peak Tuesday near the east side average, the slowly drop Wednesday 9/30.
Mid Friday on breakers from 180-220 degrees below the seasonal average.
Heights are predicted to increase Saturday.
A pair of austral sources are expected to overlap this weekend making for above average surf.
The first source is running slower and lower than predicted 9/25, but well too early to write it off.
The first pulse was generated by a gale to severe gale, low-pressure system south of New Zealand 9/17 that took a NE track allowing a better aim of seas towards Hawaii.
Given the better aim at Hawaii and similar location, duration, and magnitude than recent sources that produced above average south swells, this one was notched up in the forecast.
Readings from the PacIOOS/CDIP American Samoa buoy 9/21-22 suggested the event filled in by midday Friday.
The NOAA southern Hawaii buoys 51002 and 51003 do show wave energy in the 16-20 second band late morning 9/25 that suggests the event filled in overnight Friday into Saturday above average.
This event should peak late Saturday as a new event adds to the mix.
The second pulse was created by a low-pressure system that dropped to 948 mb to the S to SE of New Zealand 9/19-20 with seas 30-40 feet aimed at the Americas.
The wide, long fetch gives better odds for angular spreading to deliver surf in Hawaii.
The onset stage is due Saturday 9/26 from 180-200 degrees.
The American Samoa buoy showed 18-22 second forerunners 9/23-24.
This buoy location is west of the predicted primary swath, so any energy registered increases the odds for Hawaii to receive the event.
This event should slowly build into Sunday 9/27 from 180-200 degrees, with the combo of sources making above average surf 9/27.
Heights should hold above average into Monday 9/28 from the same direction, then slowly drop to background by 9/30.
, models show a gale low in the Tasman 9/26-27 that could bring near average surf locally 10/3-5 from 208-220 degrees.
The low-pressure pattern shifts eastward with a large, severe-gale modelled to slowly track east to the S to SE of New Zealand 9/28-30.
This suggests above average surf locally from 180-200 degrees 10/4-7.
It is too early for specifics.
East side should hold below average 10/1-3.
North shores are modelled to have overlapping sources from NW to N within 10/1-4, with peak days near the October average.
Long range forecasts are subject to low confidence.
The next Collaborative Forecast will be updated Monday, September 28.
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 https://www.
weather.
gov/hfo/marine

Collaborative Surf Discussion (html formatted)

DISCUSSION: SUMMARY.
.
.
.
Last week of September in seasonal transition mode with surf from around the compass.

DETAILED:.
Mid Friday on northern shores breakers from 345-360 degrees above the September average.
Heights are predicted to trend down over the weekend from the same direction.

This first overhead swell of the fall 2020 season was generated by an occluded low-pressure system in the Gulf of Alaska 9/21-23.
Highest seas were aimed NE of Hawaii.
NOAA buoy 51000 NE of Hilo was much higher than 51001 NW of Kauai through the event 9/24-25.

The midday 9/25 51000 readings still show active swell.
Surf is expected to hold above the September average into Saturday then fall below average Sunday from 345-010 degrees.
The tail of the fetch of near gales was near the eastern Aleutians into early 9/23, placing the end of the event by late Sunday or early Monday with small breakers.

A long-wave jet stream pattern is expected to form 9/27 with axis near the longitudes of Hawaii with several reinforcement short-waves from the NW to keep it active into 10/3.
At the surface, a complex, broad, low-pressure pattern with a series of low centers are modelled to unfold NNW to N of Hawaii this weekend and holding much of next week.
This should equate to an active NNW to N surf pattern locally under gentle breezes 9/29-10/3.

The first fetch of the new complex low-pressure pattern is due to set up Saturday with strong to near gale winds about 1200 nm away over the 330-340 degree band.
This should bring up surf near the September average on Tuesday.

The low center associated with the first fetch is modelled to track NE toward the Aleutians and gain gale status 9/26-27.
At the same time, another near gale low is modelled to form NNW of Hawaii near 40N, 160W, pushing a fetch within 1000 nm 9/28.
Stay tuned for specifics, with both of the sources suggested to trend surf up 9/30 from within 320-360 degrees near the October average.

Mid Friday on eastern shores has breakers from 60-90 degrees below the trade wind swell average.
Heights are predicted to decrease on Saturday with northerly exposures topping the height, aforementioned.

Remnant of tropical system Lowell is modelled to steadily track towards Hawaii along 20N 9/25-29 with a slow weakening trend.
High pressure north of the remnant should allow enhanced trades to strong levels with pockets of near gales.
This should result in a remote-source wind swell.
It is due to build Monday 9/28 from 70-90 degrees, peak Tuesday near the east side average, the slowly drop Wednesday 9/30.

Mid Friday on southern shores breakers from 180-220 degrees below the seasonal average.
Heights are predicted to increase Saturday.

A pair of austral sources are expected to overlap this weekend making for above average surf.
The first source is running slower and lower than predicted 9/25, but well too early to write it off.

The first pulse was generated by a gale to severe gale, low-pressure system south of New Zealand 9/17 that took a NE track allowing a better aim of seas towards Hawaii.
Given the better aim at Hawaii and similar location, duration, and magnitude than recent sources that produced above average south swells, this one was notched up in the forecast.
Readings from the PacIOOS/CDIP American Samoa buoy 9/21-22 suggested the event filled in by midday Friday.
The NOAA southern Hawaii buoys 51002 and 51003 do show wave energy in the 16-20 second band late morning 9/25 that suggests the event filled in overnight Friday into Saturday above average.
This event should peak late Saturday as a new event adds to the mix.

The second pulse was created by a low-pressure system that dropped to 948 mb to the S to SE of New Zealand 9/19-20 with seas 30-40 feet aimed at the Americas.
The wide, long fetch gives better odds for angular spreading to deliver surf in Hawaii.
The onset stage is due Saturday 9/26 from 180-200 degrees.
The American Samoa buoy showed 18-22 second forerunners 9/23-24.
This buoy location is west of the predicted primary swath, so any energy registered increases the odds for Hawaii to receive the event.

This event should slowly build into Sunday 9/27 from 180-200 degrees, with the combo of sources making above average surf 9/27.
Heights should hold above average into Monday 9/28 from the same direction, then slowly drop to background by 9/30.

Into the long range, models show a gale low in the Tasman 9/26-27 that could bring near average surf locally 10/3-5 from 208-220 degrees.
The low-pressure pattern shifts eastward with a large, severe-gale modelled to slowly track east to the S to SE of New Zealand 9/28-30.
This suggests above average surf locally from 180-200 degrees 10/4-7.
It is too early for specifics.

East side should hold below average 10/1-3.

North shores are modelled to have overlapping sources from NW to N within 10/1-4, with peak days near the October average.

Long range forecasts are subject to low confidence.

The next Collaborative Forecast will be updated Monday, September 28.

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 https://www.
weather.
gov/hfo/marine

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NWS Forecaster and NCEI Pat Caldwell

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