Waves, Winds, Weather compliments of Leahi Health Beverages
Your exclusive SNN Obs for this Tuesday Aug. 26th 630am
Partly clear with pockets of rain clouds. Light NE trade winds. Predawn 1.4' High tide @ 430am dropping out to a .1' Low tide @ 930am pushing up the rest of the day to 1.9' at 430pm.
Kaisers, Kewalos (check our new Bowls-Courts CAM); super clean straight light NE offshores. Diamond Head: Holding on the SSW at 1-2 occ 3' with nice lines and so far it's relatively clean light NE offshores. Sandy's: Down and Holding on the SSW and alittle more E wrap at a good clean 2-3' and still a few big barrels and breaking all over. East: Makapu'u: Up a notch and Holding the slightly bumpy 1-2.5' on generic local trades and now on the longer period 12 second East the left to Ala Moana,
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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)
Aug 26, 2014 4:00 AM HST
We are anticipating an active swell episode later in the week. In a rare case, the east facing shores are forecast to have some long period swell of 17 seconds at 4 to 5 ft generated by tropical cyclone Marie, located some 2380 miles east of the Big Island. Its long period and sufficient size of the swell will likely result in a high surf advisory for exposed east facing shores.
The south facing shores will also see some action. The current moderate surf may be reinforced by a slightly larger bump about late Wednesday thus warranting a high surf advisory for Thursday through Friday. Both swells will be declining through the weekend.
No small craft advisory conditions are expected through at least Saturday. However, the long period easterly swell due on Thursday into Saturday could produce unusual conditions in east facing channels and harbors.
A trade wind regime will hold through the rest of this week as high pressure remains north of the state. The only significant change expected is the strength of the trades which will taper off some by Friday. Otherwise, the trades will continue to carry the embedded showers on to the islands, affecting the windward and mountain areas. At times, a shower or two will drift downwind into the leeward communities of the smaller islands. The Kona slopes of the Big Island will continue to experience afternoon clouds and showers.
A trade wind regime is expected to last through the rest of this week and into the weekend. The source of the trades is being passed on now from a weakening high to the northeast to a new and stronger high located far north northwest of Oahu. This new high is easing eastward and will be directly north of the main Hawaiian islands Wednesday where it stalls and weakens. The response to this will be the moderate trades lowering to light by Friday. This period of light trades should last about 2 days with moderate trades back in place by Sunday night. Usually the light trades will be weak enough for daytime seabreezes to develop along leeward beaches and interior areas of the smaller islands. This convergent wind flow over land will result in some afternoon clouds and possibly a shower or two. The models though, are showing a stable air mass settling over the islands Wednesday night that lower the inversion from the current 10k to 8k. This would help limit the convective activity to isolated into the weekend. The weakening of the high is being attributed to the dissipating remnants of tropical cyclone Lowell moving to an area northeast of the islands where it will disrupt the trade flow destined for the Hawaiian islands.
The pop grids reflect a drier regime between Wednesday night to only Friday morning. The pops for the weekend reflect remnant moisture from the cyclones reaching the island but that is questionable at this time.
At the upper levels, we have a low roughly 470 miles west northwest of Kauai that is moving further away. The southerly winds aloft over the Hawaiian islands will become westerlies by Wednesday as the low continues west and dissipates. An east to west oriented trough will then form north of the islands straddling 28°N latitude. So in short, there are no upper level disturbances to affect the islands.
In the mean time, one band of showers has cleared the islands, another one will be here shortly, within an hour. After a brief pause more shower bearing clouds could be arriving. I emphasize could since precip water from satellite imagery shows a drier air mass with these clouds now entering the offshore waters northeast of the islands, behind the second band. These clouds are out of radar range at this time, so i am not sure how much showers are with these clouds. I have decided to go drier never the less for this afternoon, with the possibility that these clouds may keep the afternoon hours on the showery side.
BIG SURF PICTURE 8/26/14
The Jet down under has been dominant with equatorial bound (ENE) flows leading to plenty surf, but the last few days its been zonal (west to east) with 2 branches staying the same most this week. By Thursday/Friday there’s another ENE tilt which will enhance a big storm but it'll be sending much of the energy off to our east since the equatorbound flow is far off NZL to under French Polynesia.
Recent: We’ve had nonstop surf for about 2 weeks; 2 Lows tracked SE of NZL Thursday 8/7 and these sources created surf the 1st weekend for the Dukes Oceanfest! Then a powerful Low a few days after with 55kts saw into our window SE of NZL hugging the East coast with a captured fetch. We got 18 sec forerunners Wed the 20th reaching 3’ 15 sec swells or 2-4+ SSW surf Thursday midday and the final Dukes weekend…one of the best weeks for the OceanFest in over 5 years.
Currently, we saw some 4’ sets from the SSW this past F-M from 2 sources: a gale 40kt storm east of NZL mid August. Her fetch head got to 3500 miles away which allowed for head high sets. Then a stronger system further SE of NZL with 47kts added more size over the weekend and into Monday. Some spots peaked 5’ over the weekend but these were special cases/spots. Things level off to head high Tuesday.
Next: Another compact Low SE of NZL tracked east again last Monday-Tuesday and will keep us at 3’ solid before a SSW swell arrives Wednesday.
Next: The Jet set up a long wave trough from Wednesday the 20th. We also saw a big High in the Taz which created solid winds in between the High spinning counter clockwise next to the Low spinning clockwise (opposite spins from the NPAC). This allowed a huge fetch area east of NZL last Thursday-Saturday. The head of the fetch got to within 3000 miles which is about 1000 miles closer than the usual. This means less ocean swell decay over distance and another round of advsry surf filling late Wednesday peaking Thursday into Saturday and even Sunday…High Surf threshold for South swell is 8’ crest to trough which is what typical surfers look for. The NS needs 15’ or twice the size which most surfers don’t look for. Why the large difference is likely extra safety precautions where populations are greatest.
Next: : Models backed down big time on their output a week ago for a new event early Sept. A broad gale Low far east of NZL reached near Tahiti last weekend. Now, it’s going to be 1-3’ South Sunday-Tuesday.
Last couple: Low confidence of models showing a big broad storm up off the Ross Ice Shelf Wed the 27th which fades fast and followed up fast by a much bigger Low Thursday. The issue is the ENE track but side band swell should hit 3 maybe 4’ with long periods Thursday sept 4-6th. Let’s take a better look this weekend.
The weak Jet up North is continuing it’s summer position with poor potential for swell enhancement, and tho’ she’s elongated the winds are too light for anything. Most the deeper troughing occurs under the gulf toward the end of the 7 day forecast.
Recent: It’s been quite and average after the long run of Typhoon West swells and Hurricane N swells making Aug the best in memory. Reliable sources like Pat Kelly with over 40 years up there plus, a former NS Capt and SNN eye’s on the country claimed it.
Next: East wrap from hurricane Maria will send long 2-3’ 14-16 second periods producing surf up 4’ around Kahuku and less to select spots toward Haleiwa starting Thursday and into the weekend.
Next: nothing is on the models out over 10 days.
Recently, small 2’ East swell have been dominant but that’s increasing today from 2 Tropical systems: Lowell and Karina off Baja and weakening. Then it goes up big time with a rare push of 14- 17 second East surf from Cat 5 Hurricane Maria tracking ENE off of Baja (see below). Surf on the windward spots will reach as high as 7’ local scale. We also have two 1030mb High up beyond 40 north or 1200-1500 miles away keeping us in the typical trade wind pattern. So after this upcoming run its back to normal by next Wednesday.
Tropics: Cat 5 Hurricane Maria built this past weekend SSW of Baja and is expected to move NW and weaken to a Tropical Storm before Friday staying over 1200 miles to our NE. She built 40’ seas and will send off some of that High surf advsry East swell Thursday-Saturday. The main feature will be the long periods which refract and shoal off the ocean floor much more than the typical 8-10 sec windswell we usually ride. Watch for spots to break with more power and current.
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|