Waves, Winds, Weather compliments of 'Eddie Wen Go' at Hawaii Theater Tonight & Saturday
Your exclusive SNN Obs for this Friday Sept 19th 630am Update
Super clear with light ENE Trades mixing lite convective onshore seabreezes late morning. Low tide was 7am @ .4' pushing up to a 1.9' High tide at 130pm dropping out to a 0.3' Low tide at 830pm.
breaking from outside to Chambers. East: Makapu'u: Holding the small below normal NNE 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 1-2 barely 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 1-2 occ 2.5'
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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)
Sep 19, 2014 3:30 AM HST
Light winds through the weekend will allow local land and sea breezes to form. Expect increased clouds and showers across mauka areas each afternoon and evening, followed by clearing at night. Hot and muggy conditions will continue until the return of moderate trade winds early next week. Increasing moisture south of the islands may bring an uptick in rainfall for the Big Island today through the weekend.
A weak ridge of high pressure extends from a 1020 mb high near 37°N 138°W through 30°N 160°W and 29°N 180°W, 600 miles or so north of the main Hawaiian islands. A front digging into the northern flank of this ridge between 150°W and 170°W will gradually approach the islands, putting a big dent in the ridge and keeping local trade winds light at least through the weekend.
Satellite loop showed sluggish 10 mph east to west flow across local waters, and broken to overcast clouds noted across mauka areas of the islands yesterday showed that this light flow is not strong enough to prevent the development of afternoon sea breezes. Cloud cover and showers have decreased overnight, leaving mostly clear skies across much of the state this morning. Little has changed since yesterday and we expect a convective pattern to repeat each day through the weekend, with clouds and showers increasing each afternoon and evening, followed by clearing late at night.
Models show the front will push to the east Sunday, allowing the ridge to strengthen to our north. We expect light trades will return to the eastern half of the state Sunday. However, most leeward areas will still experience sea breezes as the trades filter in. Relief from the current hot and muggy conditions should come Monday as the ridge continues to strengthen and moderate trade winds build in.
Rainfall and humidity may pick up over windward and southeast sections of the Big Island today through Sunday as an area of tropical moisture skirts by to the south.
Weak trade wind flow overnight will be replaced by gentle sea breezes this afternoon. Mostly cloudy skies will persist along windward slopes of the Big Island through the remainder of tonight, tomorrow, and beyond. Elsewhere, expect increasing clouds beginning early this afternoon and lingering through most of the evening due to diurnal convection. Isolated MVFR cigs possible in passing showers today, especially windward Big Island. Otherwise prevailing VFR expected all areas.
Winds will remain light through the weekend with trade winds picking up 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|