Planetary Exloration on Senta II

Vessel Name: Senta II
Vessel Make/Model: Ericson 39B
Crew: Nancy & Sven
Extra: This blog will temporarily pick up from where the www.grenander.com blog left off after our Retina Mac suffered a memory failure. Don't ask where the "p" in exploration went but do tell me how to put it back in, if you know :-)
Home Page: www.grenander.com
05 April 2015
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26 March 2015
14 March 2015
03 March 2015 | Marina Papagayo, Costa Rica
26 February 2015
19 February 2015
18 February 2015 | Marina Papagayo
16 February 2015 | Papagayo Marina, Costa Rica
15 February 2015
13 February 2015
12 February 2015 | Marina Papagayo, Costa Rica
05 February 2015 | Playa del Coco and Marina Papagayo, Costa Rica
Recent Blog Posts
12 April 2015

Still windy and we are staying, plus thanks to Dan

It has been a hectic few weeks. We had the issue with the exoneration paperwork and the National Car Reantal overcharge and then need for a survey for new insurance.

05 April 2015

Varnish and condo time !

The cabin sole has been beginning to show some real wear and the companionway door was looking like it should have used a lot more sun screen, so it was time to get ready to varnish.

02 April 2015

Mess -> hotel stay

Now that we know we are going to stay here in Papagayo Marina for the summer we went to work on some chores.

01 April 2015

We got the exoneration paperwork !

Yes, it is April Fools' Day, but we don't think it is a joke.

31 March 2015

No bad faith contract needed ?

We finally got our misappropriated Marina Papagayo National Car Rental refund. That only took almost a month and a lot of reminders and an angry complaint letter. Talk about substandard service !

26 March 2015

Cultural whiplash

This is another surprising turn of events. We're almost getting whiplash !

The diurnal Papagayo mystery

03 March 2015 | Marina Papagayo, Costa Rica
It's blowing cats and dogs out there !
Once again we have papagayos howling but we're nice and snug in the marina so other than helping others with their boats we're just relaxing.

When Nancy woke up in the middle of the night last night I woke up too and I decided to get some pictures of the Papagayo mystery that's been bugging me for the last month or two.

The up to date forecast for the winds here in Central America is as shown in the picture below.



The thing to pay attention to is the graph at the top. Sorry it is a bit blurry, handheld in low illumination can be a challenge even for our new Olympus E-M1. The two lines in the graph show the predicted winds and max gusts over time. The labeled tick-marks on the horizontal axis represent midnight in UTC (essentially GMT time). Since we are 6 hours after UTC each labeled tick-mark is 18:00 local time here.

What stands out in that predict is that the calmest period during each day is between ~11:00 up until ~18:00. After 18:00 the wind picks up and doesn't slow down until the next morning (local time).

Let's contrast that predict with what we have actually observed as the general pattern.

The picture below show what our weather station has measured over the last 24 hours. The Davis weather station is not a scientific instrument, it violates one of the most important rules of scientific measurements: Be clear about what units you are using and what scale you are measuring against. The graphed display doesn't label either axis so it is only from experience that I can guess what the labels should be. One thing that is obvious is that the right hand side is "now" and the left hand side is 24 hours ago. There is no way of telling what the upper bound on the vertical axis is and if you have non-zero wind all day I suspect the lower limit would be indeterminate too.



So, ignoring my rant about the lack of labels, we can still see the general wind pattern over 24 hours. This particular graph is actually quite typical and it completely disagrees with the predict above. The picture was taken about 03:00 and each major horizontal segment is 6 hours. What we see is the the winds are the strongest between ~09:00 and ~21:00 and the weakest between ~21:00 and ~03:00.

I should note that our "actual" measurements are near land as we tend to hide out when there is a blow outside (we are currently at the blue dot on the map). The predicted graph shows the wind at the blue cross-hair just north of Capo Santa Elena. Still, it seems really really odd that the predict and the actual should be so far out of phase.

Maybe I've made a fundamentally flawed assumption about what I'm seeing in the Weather4D Pro display regarding time ? This is still the prediction tool I use, but only for overall wind patterns, I add in my own diurnal take on when the min and max winds will happen and add to that whatever Cape or Gap effects we might have.

If anyone sees the flaw in my reasoning above I'd love to be set straight, until then I'll still be mystified.
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