Tuesday, May 23, 2017

Tuesday 5 23 17 morning call

After a lovely surf session in Lahaina, yesterday I managed to miss the windsurfing on the north shore because I waited too long for the conditions to be the way I like them. Not sorry a single bit, for a change here's a photo of a kiter showing the waves (which occasionally were up to mast high or 4m faces). Photo by Jimmie Hepp from this gallery.

3am significant buoy readings
South shore

No signs of any energy from the south at the buoys, but that's only because the new NW energy is shadowing it. These are the kind of things you learn when you observe the buoys for as long as I have. What counts in this cases, is the knowledge of the original fetch (which I posted in a collage yesterday) and, if the sun is out, the webcams of course. My guess in the dark is that there's still waves.

Here we go, I decided to wait to have that confirmation and sure enough I immediately caught a chest high one. Might have been the set of the day, who knows. What I was afraid of, and seem to show watching the live feed, is a bit of wind texture caused by the fact that today the trades are going to be kinda strong and that usually brings some turbulence also on the other side. Might clean up though.

In the meantime, here's the graph of the Samoa buoy that shows the swell that is forecasted for the weekend picking up mid yesterday (red circle). As illustrated in the post Buoys to Maui travel times and Maui's shadow lines , the travel times from it to here are according to the following table.

20sec--30kts-- 74hrs (3days)

17sec--26kts-- 85hrs (3.5 days)

14sec--21kts--106 hrs (4.5 days)

11sec--17kts--130 hrs (5.5 days)

The first recorded reading seems to be 2f 16s around 8am Monday (there might be smaller ones with longer period before it). Those will take a little more than 3.5 days to get here and that means Thursday evening. In the meantime, they will also lose some size and gain some period. As a result, the Surfline forecast calls for 0.8f 18s at 8pm on Thursday. Considering how inconsistent a south swell is at the very beginning, we can safely say that the first day of the swell is going to be Friday.

North shore
10.3ft @ 8s from 62° (ENE)

4.5ft @ 12s from 306° (WNW)

5.3ft @ 11s from 329° (NW)

5.5ft @ 8s from 350° (N)
4.4ft @ 11s from 334° (NNW)
NW Swell still up at the buoys, plenty energy on offer also today. If you remember the fetches, you'll know that this is going to be a long lasting swell, with decreasing period and size hand in hand with the direction going progressively more easterly. If you don't remember the fetches you have two options:
1) scroll down to the past day's calls and check them
2) read the wordy explanation of Pat Caldwell:
A long-lived, broad area of low pressure moved slowly east from the dateline along 40°N 5/18-21 as peak winds slowly weakened. Strongest winds aimed NE of Hawaii. There was a short-lived spell of 13-15 second wave period energy late 5/21 locally as measured by the pacioos/cdip Waimea buoy. The energy is dominant in the 10-12 second band mid Monday 5/22. The primary fetch aimed at Hawaii was of strong to near gale winds over the 320-340 degree band, closest on 5/20 about 800 nm out. Fresh to strong breezes over the 330-360 degree band nosed even closer to within a few hundred miles while the tail of the fetch was beyond 1200 nm away. This should make for a long-lived episode as the dominant direction veers from NNW to N then to NNE.

Overhead also today is my size guess, but with the Hookipa sensor already reading 9(6-12) from the east at 5.20am, I might not even go have a look. I like clean waves.

2pm wind map shows easterly trades and another good day for wind related sports.

Current wind map apparently only shows a NNE windswell fetch.

But with my surprise, the Meteogram automated generated fetch map shows a fetch down south.
That map (right of the photo) is at 6Z which is 8pm Monday, and the Windy map (left of the photo) is current (5am this morning), so there's a bit of time difference between the two, but the reason the fetch I circled doesn't seem oriented towards us is that the closer you get to the poles, the more distortion gets introduced when you try to represent the Earth on a flat map. That's why the Great Circle Rays maps are an important tool.

Now the problem with that fetch is that is about one more extra day of travelling distance and considering it only has up to 30-34 knots wind in it, I believe that the related wave energy will have a hard time make it all the way up to Hawaii. We will see in 7-8 days.

Morning sky. Watch out for the trade's generated squalls on the eastern sides of the island.

Watch out also for some really shallow low tides coming up this week due to a spring new moon. Here's Kahului. Lahaina is roughly one hour later than that.

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