Waves, Winds, Weather compliments of Big City Diner
Your exclusive SNN Obs for this Thursday Oct 2nd 620am Update
Clear and stablizing atmosphere. Calm to Light trades give way to cloud build up and seabreezes from about 11a for many areas. High tide 11a 2'. Low tide 630p 0.3'.
East: Makapu'u: holding the small East swell 0-1 barely 2' breakin' inside but its smooth fun and good diving. Diamond Head: Down and dropping from the SSW at 2-4' and even some +' toward Black Point on sets on the take off & it's good-excellent with light offshores. (see SNN Cam). Sandy's:Down and dropping on the SSW with clean 2-4' sets at Generals, smaller at Full and half Pt and into the big close out shorebreak.
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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)
Oct 02, 2014 3:30 AM HST
Light trade winds today and Friday will yield to light and variable winds over the weekend, continuing into next week. The light trades will deliver a few showers to windward coasts and slopes, while also allowing afternoon clouds and showers to develop over interior and leeward areas. Some showers may be heavy this afternoon. The light and variable winds over the weekend will lead to mostly clear nights and mornings, with afternoon clouds and showers favoring interior and upslope areas. A more stable air mass developing over the islands should limit shower intensity by the weekend, but muggy conditions will continue.
It's been a relatively quiet night, with light trade winds pushing a few showers ashore along windward coasts and slopes. While radar shows that some of these small showers have intense cores, coverage is limited. Latest surface analysis depicts a surface ridge within 100 miles N of Kauai, extending SW from a high centered about 1900 miles NE of the islands. With the ridge in this position, a light E to SE flow exists in the low levels, with island-scale land/sea breeze circulations overriding this flow. A weakening low aloft centered about 550 miles ENE of Oahu is moving slowly E, while an associated weak trough extends W over the islands. High clouds S of the trough axis are streaming over the Big Island and adjacent waters.
A somewhat less active weather pattern is expected to develop over the islands the next several days, as the low aloft weakens and a slightly drier airmass moves in from the E. Models indicate that a weak trade wind flow today will persist through Friday, as the ridge drifts slightly N. Still expect afternoon seabreezes today and Friday to drive interior and leeward clouds and showers. Morning balloon soundings indicate that a moist and unstable air mass remains in place, with the PHLI sounding indicating cape values in excess of 3000 j/kg. Thus locally heavy rainfall appears possible once again this afternoon, mainly interior and leeward. Showers are not expected to be as widespread or intense on Friday. High clouds near the Big Island should trend towards clearing out today as the trough aloft weakens.
During the weekend and into the middle next week, a cold front several hundred miles NW of the state will move slowly SE, pushing the surface ridge over the state, supporting a pure land/sea breeze pattern over the islands. Scattered showers will develop mainly across interior and leeward areas each afternoon, with clearing each night as land breezes take over. Developing light SE background flow may allow areas of volcanic haze to spread over the smaller islands during this time. The front is forecast to retreat northward by the middle of next week, allowing the ridge to shift N, and a light trade wind flow is expected to return. Warm and muggy conditions will continue through the forecast period, with above normal sea surface temperatures contributing to rather high dewpoints.
Vfr conditions and light winds will prevail this morning. Sea breezes will produce low clouds over the leeward and island interior sections by the late morning. Mvfr cigs, tempo mtn obsc will be possible by this afternoon as the clouds build through the day, and airmet sierra may be necessary. Instability across the state will allow for some of the sea breeze driven clouds to produce locally heavy rainfall, reducing visibility at times.
Buoy data indicate that the current S swell remains sufficiently high to maintain advisory level surf along S facing shores today, with surf expected to decrease below advisory levels tonight. No other significant S swells are expected through the weekend, with a minor pulse of S swell expected from Monday through Wednesday. A moderate NW swell that peaked Wednesday will gradually subside through Friday, just as a new moderate NW swell begins to build. This swell is expected to peak late Saturday and diminish into Monday, just as another similarly-sized NW swell begins to arrive. Resultant surf is expected to remain below advisory levels along N and W facing shores. After a bit of a hiatus, the Oahu surf discussion /srdhfo/ was updated yesterday, and contains details that can be loosely applied statewide.
Winds and seas will remain below small craft advisory levels through the forecast period.
BIG SURF PICTURE
The Jet down under is still looking good for storm enhancement and steering toward the Islands. There’s a thick North branch and a decent southern branch flowing NE from off NZL the next few days. However, the high pressure are trying to squeeze out the troughs and block off NZL around Monday the 29th. Still, we get the N bound flow under Tahiti at this time allowing for more energy to come our way. Looking good.
Recent: We’ve been on the down trend to 1-2’ background SSE for awhile but that’s all going to change again for a super long round of back to back to back SW-South swell.
Next: A small bump from a Taz Sea fetch last Friday should pop 1’ 14 seconds on Barbers Buoy late Friday and rise into Saturday with long lulls of 1-3’ surf into Sunday. This will be overrun by the next source.
Next: The above Taz storm drifted east over NZL and gets out of to the NE side by Monday with a 40-45kt fetch nosing to about 3000 miles to our SSW or 1000 miles closer than the usual region of swell generation. Reinforcing SSW could hit 2-4’ Tuesday-Wednesday.
Next: Far below the above fetch is a much bigger stronger Low to the SE of NZL tracking ENE M-W and will add to the existing seas of the first Low to the NE. The apparent fetch from these two mergers gets nearly 1000 miles long creating yet another long lasting episode of fun in the sun and surf. Forerunners could pop 22 seconds Sunday night the 28th but it will be a slow rise over Monday-Tuesday. Still top reefs could see some 5’ sets Tuesday night and peak near 3-6’ on Wednesday-Thursday. We will have 2-3 days of high surf advsrys.
Next: Within the large Jet stream trough is yet another Big Low with its reinforcing broad 40-45kt fetch building 30’ seas Wed the 24th. Plus, the track is NE garnering a captured fetch (fetch points the same way as the storms center track) which helps grow the seas to their full potential. Thursday the track veers East under Tahiti so this swell will start out SSW and veer S. There’s a ton of storm activity far below French Polynesia so Tahiti’s going to score.
Next: Saturday the 27th shows a smaller compact Low tracking NE from below NZL which will bring up some 2-3’ SSW Saturday the 4th.
Last: Too early to claim but WW3 hints a whopper under Tazmania Oct 2nd…
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.
Wednesday the Jet Stream is split 1200 miles off Japan with a larger trough looping up and down under the east Aleutians which leads to the first big NW hitting the NW coast. The fall regime change in the Jet is conducive to 3 rounds of fun NW swell. The split moves our side of the dateline by Saturday the 27th then consolidates and fattens up Sunday-Tuesday with a large dip SE near the dateline just 1200 nearing to 900 away. This will likely mean lighter winds and iffy weather early Oct. But it also spells WAVES.
Recent: It’s been tiny 2’ or less with minor pulses here and there from the NNW however, that changed today.
Currently: the surf has bumped up to 3’ Wednesday afternoon from the NW. We had a powerful Low off Kamchatka last Friday and it stayed over 2000 miles away limiting the size to max 3’. There’s also a N mixing from a nearby Low 1200 miles to our N. This is the same storm that intensifies as it tracked E toward the west coast so we’ll get N to NNE into Saturday. They’ll be 8 and even 10’ for N Cali and Oregon etc.
Next: Thursday-Friday the NPAC looks quite with only a tropical storm far off Taiwan building and tracking N to Japan. Hold on to this one.
Next: Upgrade for Saturday's storm: a Low spawns of the Kuril Islands with up to 30’ seas and a nice ESE track with a partially captured fetch; it reaches the dateline Sunday the 28th. Look for 5’ 16 seconds buoys oct. 1st refracting/shoaling swell for some 5-7' NW surf at Sunset Wed afternoon into Thursday morning. Could see some high surf advsry sets.
LAst: On Tuesday the 30th the tropical system above becomes a gender bender (warm to cold core Low) and feeds into the Jet energy near the West Aleutians intensifying Wed-Thursday as it moves N into the Bering sea. Still, tho’ distant its forecast to be powerful enough for 16 second forerunners and some more 4-6’ NW surf filling Sunday Oct 5th into Monday. Iffy confidence.
Windward side: With the return of the trades we’ve had a boost to 1-2’ ENE and we’ll also get some small N wrap from the above NPAC source. The surf should range from 2’ to maybe 3’ due also to a shear line moving South across the Island into Thursday. This is an abrupt change in wind speed and/or direction.
Tropics: A powerful system is on the charts Tues-Thu far off the Philippines moving NE. Too early for specifics but it's likely to be a typhoon. Things have calmed down off Baja.
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|