Waves, Winds, Weather compliments of Leahi Health Beverages
Your exclusive SNN Obs for this Monday Sept 15th 630am Update
Same story. Perfect morning. Another hot and sunny one. Calm to light Trades are with us now but watch for lite convective onshore seabreezes midday with cloud build up into the afternoon. This pattern is set into Wednesday. 1.8' High tide at 10am dropping out to a 0.5' Low tide at 630pm.
Still above High Surf advsry for all southern exposures. Buoys are 4.5' 17 seconds. Ultra inconsistent. Some reefs did see some 8' sets Sunday at top spots. Most spots 5'.
; all over, plus generals and heavy shorepound. East: Makapu'u: Holding the small below normal ENE and S wrap 0-1.5' on the shore and semi smooth lite onshores. Great diving all windward. Diamond Head: Up and holding on the SSW at 3-5+' with superb glass to offshores but likely onshores 11am ish then to the evening glass off. (see SNN Cam). Sandy's: Up and holding on the SSW at a nice clean 3-4 occ 5'
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THE WHERE, WHEN & WHY OF HAWAII’S WAVES & WEATHER: A VIDEO PRESENTATION BY SNN
Winds Statewide in a glance ...go HERE (this link is also the 4th drop down under weather)
Issued: Sep 13, 2014 4:11 AM HST
Winds and seas are expected to remain below small craft advisory levels through the forecast period.
A very long period south swell will build through the day. Current readings from buoy 51004 suggest the higher period swell taking over as the dominant period, but heights have not jumped up yet. Surf along south facing shores is expected to reach advisory levels by this afternoon. The surf is expected to remain elevated through Sunday night, before slowly diminishing next week.
Elsewhere, a short-lived moderate northwest swell is expected to arrive late in the day Sunday, and gradually diminish through the first half of next week.
A diurnal land and sea breeze pattern will persist through the middle of next week bringing warm temperatures, afternoon clouds with showers, and clearing during the nights. Additional moisture will move in Sunday leading to more shower coverage, through rainfall amounts are not expected to be significant.
Current satellite and radar shows clouds and showers have increased over the Big Island, and windward Maui and Molokai this morning due to an influx of moisture coming in from upstream. Soundings from this morning shows an elevated inversion of 12000 feet at Hilo and a relatively moist precipitable water value of 1.55 inches. Expecting this moisture to remain over the Big Island today and tonight before transversing westward. Isolated showers are also impacting the windward side of Oahu.
A surface ridge is present over the islands resulting very light pressure gradient and winds. The light wind flow regime will result in warm conditions today. Sea breezes from heating of the land will produce clouds and showers over the interior of the islands from late morning to early evening. The Big Island will see the greatest areal coverage of showers extending up to the higher elevations today. Land breezes will break up the clouds and showers tonight. This diurnal weather pattern will continue through at least the first half of next week.
The models bring varying amount of precipitable water into the islands starting Sunday through most of next week, though the trend is that it will increase. The atmosphere is expected to remain stable, so the additional low level moisture will likely mean an increase in the number of showers for all islands, with most shower activity occurring during the afternoon and early evening hours. It is possible we may see isolated moderate or heavier showers at times, but overall atmospheric dynamics does not support any elevated chance for this.
A large deep layered anticyclone will build slowly eastward from the date line to the north of the state, allowing light to moderate trade winds to gradually return during late next week.
BIG SURF PICTURE
The Jet down under has gone into ‘shutdown’ mode after a large trough last week generated what we’ve been claiming since 2 Friday’s ago…the year’s biggest SSW to south swell. Summer can’t last forever. After this long lasting event we’ll have to hope and pray.
Recent: We’ve been on the down trend to 2’ after a super long run of fun South swells that reached peak hts of 5’ at select reefs but mostly sets averaged 3’ from early Sept to Tuesday the 9th. Last weekend into early last week had a pair of swells from a pair of storms down under. We haven’t counted but since Aug to now there have been at least 8 sources of swell. The last of which will top it all off. Read below.
Next: Last Sunday a powerful Low tracked ENE under NZL with near hurricane force 65kt winds and seas near 50- 60’! The storm broadened further off the coast as the highest winds and seas weakened. But not before setting up a 1200 miles fetch. When storm have such extreme winds they generate long periods as we’ve seen since Friday: long fat 25 seconds leveling off to 22 sec Saturday and 20 sec Sunday. The swell hts will go from 1’ to 4’ and even 12 hours of 5’ 20 seconds. There will be moments at select reefs of warning level hts of 15’ crest to trough or 8’ local. The North shore can get 10’ from such values as the long periods have extreme refraction and shoaling off the bottom. Note: 20 sec period swell can be felt 1000’ down! This shows us how vital periods are to wave measurement.
Last: No sources of swell over 2’ out through next weekend meaning 2 weeks from now. There are marginal fetches in the Taz Monday 15th and another tiny Low off NZL Friday the 19th. Neither source may get here.
Note: High Surf threshold for South swell is 8’ crest to trough and 15’ for NW swells. Why the large threshold difference is likely an extra safety precaution where populations are greatest.
The weak Jet is long and up around 40-50 degrees latitude. There’s some troughs and dips and by next weekend the Jet has a bit more speed and energy going from Japan to the Gulf. We are still in a state of transition.
Currently: the surf is barely 2’ remnants from our 1st real swell of the season that hit near 8’ Tuesday.
Recent: this nice WNW filled late Monday to 6’ and ramped Tuesday from a more NW angle. Source: Storminess Friday the 5th just east of the 180 dateline 1200 miles NW of us. By Saturday she had 30’ seas on the dateline and spun in place (occluded) as she broadened and weakened into Sunday…The result was swell of 5’ 14 seconds.
Next: Former tropical storm Fengshen will bump us up Sunday from the 15 sec WNW at 2-3’ midday and veer NW peaking at 4’ Monday into Tuesday with shorter 12 seconds. The system formed off Taiwan last Sunday the 7th and moved NNE as it broadened and weakend off Japan becoming a cold core Low off the tropics warm core. It then tracked East reaching the dateline Thursday the 11th as it merged and faded with a broad area of Low pressure centered in the Eastern Aleutians.
Last: A tiny weak low tracks east from the dateline this Wednesday and will only pull off some 2’ NW surf Tuesday the 23rd.
Recently and until Friday we’ve see tiny 1’ surf from the light local trades and seabreeze patterns; rare to see it this small this long. Then it’ll kick up from some T Storm action below.
Tropics: T Storm Odile has come into view today Sat. with a NW track and clipping Cabo etc Monday-Tuesday. By Thursday it’s nearly gone but still may shoot out some longer period 3’ East swell around Friday-Saturday the 19-20th.
FETCH: Often called the fetch length, is a term for the length of water or distance over which a given wind direction has blown. Fetch length along with the wind speed (or strength) determines the size of waves produced. The longer the fetch length and the faster the wind speed, the larger and stronger the wave will be and vice versa.
CAPTURED or FOLLOWING FETCH: Not only does the fetch length determine the power and energy of the wave. Additionally, if the winds/fetch are blowing in the same direction as during the wave's or storm's lifetime, the wave will in turn be even stronger. The fetch is related to the orbit of the wave and track of the storm.The longer the wind drags along the sea the more energy the wave will have. This can be seen not just in vertical height measurement but in wave period (the measurement of waves through time).
WAVES PERIOD:Time, in seconds, between the passage of consecutive wave crests past a fixed point. In general the longer the period the bigger the wave. Windswell or 'close interval' swells are under 10 seconds. Big 'ground swells' are 17-20+ seconds (note: a 20+ second swell needs storm force 50+kt winds blowing over a 1500 mile fetch to be fully developed' into 20-25' beasts; these 20 second waves can be felt 1000 feet down!). This is why they jack so much more, pulling large amounts of H2O off the outer reefs.
More generic marine definitions click this link http://www.prh.noaa.gov/hnl/pages/marinedef.php
....All surf height observations and forecasts are for the full face surf height, from the trough to the crest of the wave.
|North-Facing Shores||15 Feet (8')||25 Feet|
|West-Facing Shores - Big Island||8 Feet (4'+)||12 Feet|
|West-Facing Shores - Remaining Islands||12 Feet (7')||20 Feet|
|South-Facing Shores||8 Feet (4'+)||15 Feet|
|East-Facing Shores||8 Feet (4'+)||15 Feet|