BIG SURF PICTURE Thursday 12/18/13 NPAC
The Tokyo express is full speed ahead (200kts). Indeed, the Jet Stream is deep, low and consolidated from west to east, off Japan all the way to our north just 1200 away. Our Jet is steering and enhancing Winter Caliber Lows which finally look like normal 'Fat WNW-NW ground swells'. There's 2 on the charts.
Currently: A rising WNW at 8' 14 seconds is the 1st phase of the broad Low from last Sunday/Monday. It's complicated: a mother Low has 2 babies spinning in her womb with spins of their own. They can merge. It's called the Fujiwara effect and its fairly rare and leads to long lasting episodes with pulses within pulses.
By Tuesday the large circulation builds but sends some of its energy to our SW. Plus, there's the extreme West angle leading to 'shadowing' from Niihau and Kauai (275-294). So it's tricky to forecast specific breaks and specific times. Still, the biggest portion should be served Friday at 10-15+' if all goes well. WW3 has downgraded this one to 8' 16 seconds which would be only 12'. Bummer if this turns out.
This WNW will get 'reinforced' Saturday by the 2nd Low and be about 8-12+' then drop from there. But wait there's more.
Next: A powerful Low kicks off Japan this weekend with 48' seas and a zonal or west to east track making to the dateline as its mellows. Still, the energy hangs out into Tuesday leading to another big- fat- long lasting- double reinfored event Christmas Eve into Christmas Day and again thursday the 26th. Forerunners will be 5' 22 seconds. The Swell should peak at 10' 20 seconds which is enough for easy 15' and bigger 12/25. Another 15+ pulse likely 12/26. It's still way out there and models do tend to run 'hot' or overcall. But expect Warnings either way.
We have an out of season S to SSE event hitting near 3' today for top spots top sets. The cause was a fetch south of Tahiti over a week ago.
We go quite after this. Real quite.
Minor Trade swell from the East at 2' average. The big storms and winter weather are making for harder predictions as they affect wind patterns. Still, 'average' of 2 mayb 2.5' is the claim.
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