Waves, Winds, Weather compliments of 'Eddie Wen Go' at Hawaii Theater Friday
Your exclusive SNN Obs for this Thursday Sept 18th 630am Update
Clear, calm to light ENE Trades giving way to 11am lite convective onshore seabreezes with more cloud build up into the afternoon. This pattern is set into Monday. Low tide 6am @ .4' pushing up to a 1.8' High tide at 1pm dropping out to a 0.3' Low tide at 8pm.
The best South swell of the year has eased another notch with Barbers Buoy are 3' 13 seconds.
; all over and still some powerful shorepound. East: Makapu'u: Holding the small below normal NE 0-1 barely 2' near the shore on the Keiki's side and semi smooth lite onshores. Great diving all windward. Diamond Head: Down and dropping on the SSW at 2-3' with nice light offshores but likely onshores 11am ish then to the evening smooth off. (see SNN Cam). Sandy's: Down and dropping on the South at a nice clean 1-3'
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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)
Sep 18, 2014 6:57 AM HST
Island skies have cleared early this morning with land breezes pushing most clouds and showers offshore. Expect increasing clouds late this morning and through the afternoon with a chance of showers.
Weak high pressure north of the area will keep light trades across the islands during the next few days. Seabreezes will develop with clouds and showers returning each afternoon and evening, especially over leeward and interior areas. The light winds will also keep generally warm temperatures across the area. Increasing moisture south of the islands may bring an increase in rainfall over the Big Island late in the weekend.
Weak sfc high pressure remains located far N of the aloha state, keeping weak trades across the area through at least Sat. A mid/upper level ridge is also located N of the island chain. This synoptic scenario will allow for more seabreeze circulations to develop each day, with periods of clouds and showers during the afternoon and early evening hours.
Meanwhile, models remain in fair agreement regarding a cold front passage across the N central Pacific during the next few days. This front will further erode the high N of the aloha state and enhance the seabreezes. Most the resulting shower activity will include leeward and interior areas. The light winds will also allow for volcanic haze to build around the Big Island, but so far it is not expected to reach the smaller islands as the light winds should still remain generally from the E.
For the long range forecast, models show a possible tropical disturbance passing to the S of the islands by Sun, bringing an increase in moisture and showers over the Big Island. Also, the aforementioned front stalls about a couple hundred miles N of the aloha state and gradually dissipates during the weekend. The presence of the decaying front to the N and the tropical feature to the S may cause an increase in pressure gradients across the area which in turn could bring an increase in trade flow by late Sun and into Mon. Regardless of this scenario, the high should begin intensifying early next week with stronger trades returning by tue/wed. This will bring back a trade wind weather pattern of clouds and showers favoring windward and mountain areas, especially at night.
Small swells will affect almost all shores through the forecast period. A small but new southwest swell with a long period of 15 to 17 seconds will arrive Friday and continue through the weekend. A small swell from the northeast is due in today, peaking Friday. The current northwest swell will be reinforced by another small northwest swell early next week.
Winds will remain light through most of the forecast period. The trade winds will begin increasing early 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|