BIG SURF PICTURE  Tuesday 2/21/12

NPAC:
The Jet Stream is weakening and breaking up with large areas of High pressure to our NE through our 7-10 day forecast period. The assoc. ridging or long area of high pressure over to our NE is keeping trades around and high wind swell. A front will disrupt this pattern Friday into the Weekend but models are mixed as to the timing and degree of W-SW to E-SE winds and wetter weather. Trades are likely to normalize early next week. The issue for surf is the High spreads to the dateline and all the way to the west coast by next week blocking the Lows coming off Japan. The further away a storm the more decay time for open ocean swell. This will lead to an extended period of way below average NW swell after this Sunday's 6-8 occas. 10' NW.

Currently: We had a downgrade of our most recent swell. The Jet went more North Friday keeping a Low further away at about 1800 miles. Surf from this smaller storm  ramped up from the NW with 16 seconds Sunday and peaked at 6' and is only 4' tops Tuesday and will be small on Wednesday for most the day till the next NW fills in.

Next up: another downgraded fetch formed this past Friday/Saturday in the 295-310 band of Japan and the best winds of 47kts lasted just a day. The Low moves ENE and got past the dateline Sunday with a weaker fetch but still it'll keep us going past Friday. Lets claim 4-6 maybe -7’ WNW outta this one to 4' Wednesday afternoon abd peaking Thursday with easy double overhead then down to 5' Friday.  

Next: a compact powerful( over 50kt) Low spawns of the Kurils and GFS (Global Forecast system) hints of a rapid growth and occlusion by this Wednesday 2/22; this pause in the forward track of the Low allows the fetch to broaden and build those seas in the 300-320 band with the fetch nosing just past the dateline. If the computer fantasy plays out we’ll get long 18 sec period forerunners midday Saturday and a 6-8 maybe 10’ WNW at Sunset beach by early Sunday 2/26.

Next: A compact Low moves off Japan with a ENE track this Friday 2/24 and keeps its distance west of the dateline or 1500 away. We can expect a 16 sec 4-6' WNW by Monday 2/27. There may be another smaller one on its heals for Thursday but no biggy.

SPAC:
We also had a source fetch from 2/12-2/14 due south of us to keep things rideable at 1-3' from the South. And another 2' followup around thursday-Friday. Then production down under goes quite near the end of the month into early March. But we've seen plenty 'early start up swells in recent years so no harm in hoping).

East Shores:
High pressure is firmly in place to our NE stretching to the west coast allowing for fresh trades and a long fetch through Thursday and thus the wind swell from 2-4+’ out at Makapu’u  Friday afternoon into Presidents Day and even Wednesday. Things calm down from thursday into Friday as a  front weakens the High gradient with poss. veering W-SW to ESE winds come around. Models are mixed.

Longer range outlooks have shorter attention spans.

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.

For more generic marine definitions click this link  http://www.prh.noaa.gov/hnl/pages/marinedef.php

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