Tag Archives: Weather

earth–water–air–fire*

If you have never visited

earth

Click Globe

you have missed something truly beautiful.

This site offers near-real-time super computer simulations of the planet’s weather with an emphasis on wind, current, temperature, humidity etc. It offers a stunning visual context for other weather products such as “Unified Analysis.”

earthmenufor “fire” one must go here: http://volcano.si.edu/reports_weekly.cfm

Well, We Punted on the Bahamas.

The Exumas and Abaco will have to wait until late November and beyond. Once again, we have watched a weather window close up after teasing us for seven days. Now the rush-rush (at 7 knots or less) logistics of getting there and getting back would just degrade the stay.

More than anything, the bureaucratic delay associated with turning 65 put us on  this slippery slope. At least that’s our excuse, and we’re sticking to it.

We suppose if we hadn’t been to the Abacos, we would have adjusted our criteria to include iffier weather and sea conditions (Such as we encountered on our first return.) We didn’t. We are sorry to disappoint those who were looking forward to tropical pictures. We would have liked to have taken them. Be patient, we will return, as will the photos.

So now, we will motor, motor-sail, sail the local area with a few along-shore sails thrown in to prevent rust from gathering (on us, not the boat). The average depth in the Indian River Lagoon between Port Canaveral and Fort Pierce is three feet and we draw more than five so it’s going to be interesting. This is when we envy Paul and Sheryl Shard’s Southerly 49’s shoal draft characteristics. [OBTW, It’s For Sale]

Now we have to find a supply for conch and grouper locally. Not easy. But we are interested to see how plantains mashed for Mofongo will work as a binder for conch fritters.

100 Days

On January 1st, a hundred days ago, we started keeping track of weather windows for crossing to the Abacos under sail in comfortable sea conditions — good winds, long period waves, no lingering northerly or cross swells. I know, picky, picky.

Cross hatched days in orange had other wind directions but lingering north swells made them essentially northerly wind days. The other cross hatched days were so-so/good wind days subtracted because of bad swell.

100days

Orange = BAD, Yellow = So-So, Cyan = Good, Magenta = GREAT

The upshot has been 86 of the last 100 days have been unsuitable per our criteria, and now the forecasts for good winds include thunderstorms and potentially heavy rains. The good days have been encumbered by other boat or life demands.

Patience is an attribute. (We keep telling ourselves that — daily).

Ramblin’ Windrose

Copyright © 2001-2014, Iowa State University of Science and Technology.

Copyright © 2001-2014, Iowa State University of Science and Technology. Click to Enlarge

An interesting picture. The rust colored quadrants are bad wind directions because of the Gulf Stream. The red arrows are wind on the nose for the worst crab across the Sream from West Palm (The boat has to crab as much as 45 degrees in the strongest flow of the Stream.) The green arrows are the best wind direction for a fast comfortable ride. The blue dashed line is the rhumb line between West Palm and Memory Rock. This year has actually had more “good wind” than the last two, but the heavy northerlies have  left swell behind that made the “good wind” days this year pretty much unusable. Half as many calm days (2012-2014) have also reduced the opportunity for the seas to drop. Wonder what February will reveal?

Each arm of these roses is proportional to the amount of wind of that velocity from  that direction. None of these even come close to what the Pilot Charts indicate one should expect in this region.

Even a Steady Breeze can be (a) Variable

Our wind preference for crossing the Gulf Stream

No, it’s not a new burgee, it’s our wind preference for crossing the Gulf Stream — and some greens and blues can be degraded to yellow and green by left over swell from Northerlies

As I sit here listening to the first heavy rain in weeks, I decided to share some observations about the wind forecast for the Gulf Stream which are better than anecdotal, if not quite statistically robust. What is important here is the thought process rather than the precise data. The central observation is:

How much a ten day wind forecast varies often escapes us, and forecasts of more than two or three days (text or GRIB) just aren’t very useful for spotting Stream-crossing weather windows. These observations neither transfer nor scale to other situations/areas. [All graphics can be clicked to expand.]

  • Days NoticeSince we have been stuck here in our Catch-22, there have been 11 crossable days (blue green and about half yellow — 11 out of 23) — single days sandwiched between bad ones didn’t count.
  • Persistent forecast for each of those crossable days was available 3, 4, 6, 2, 0, 0, 1, 0, 0, 9, 0 days ahead  — or an average of 2.3 days in advance.
  • If the one nine day outlier is removed, the average drops to 2 days.
  • Since we prefer to avoid the yellow days and single days, this drops to 5 crossable days with 2-3 days notice.
  • Crossable doesn’t necessarily mean enjoyable.

variableStare at the picture from a distance. Columns are the successive forecasts. Rows are the evolution of the individual daily forecasts. The last block in a row is the observed wind on forecast day. The open green boxes capture the histories of the evolving crossable windows. One can begin to see windows don’t announce themselves very far ahead.

obspredSo what have we seen as to observed winds and predictions? The best windows (in turquoise territory) are two or more days long — either leaving time for swell to abate, or time to get farther along one’s route — beyond the Gulf Stream. [The convention with each of the charts that capture wind direction is N = 0, E= 90 and S= 180 or -180 which ever was least ambiguous when plotting, and W = -90.

MaxsHow did these forecasts conditions vary with time? Here are the max easterly (N>E>S) and max westerly (N>W>S) directions predicted through the evolution from first forecast to observed wind.

Interestingly, the observed winds seem to come closer to the maximum westerly prediction and the predicted winds come closer to the easterly maxes. I’m betting this is a jet-stream driven observation, Especially since a deep south jet has been a strong influencer lately.  So can one say if the jet stream is well south, bet on the more westerly predictions? Don’t know, but I think I might since the assumption fails toward safe.

rangeofvariabilityBut just how variable were those forecasts (degrees between E-maxes and W-maxes)? The average variability for any given day was over 90 degrees* during the evolution from forecast to observed.

As you can see the data is choppy, and two of the most variable days were associated with a very good window. So wide variability is not cause for writing off a particular day — especially if one is outside the “last two days” zone.

*Somewhat biased downward by short forecast periods or short evolutions at each end of the data field.

varscatterThere are some features to variability that may be useful (or may be more jet stream). Here we can see the greatest variability was strongly associated with observed winds from the W>S (blue). This doesn’t surprise since these winds are themselves the heralds of change — of approaching Fronts.

However, while the predicted wind (yellow) directions seem to lack correlation with variability, the amplitude of the variability is as great as the observed winds. This tells the story — the best wind directions are the hardest to predict. Or, when it’s forecast to be bad, you can be pretty sure it is going to be bad, and when it’s forecast to be good, go figure.

windowtwoThe widest window (25-28 Jan), the one with one day which had nine solid days of notice, how did the variability play out? Through most of the forecast period, only the 27th looked useful. The other three days offered  no notice.

The bottom line. Be prepared and jump when nature says, “frog.”

It Isn’t Always Velcro…

StucknessVero Beach is often called Velcro Beach because a lot of cruisers stop here and go no farther, to include swallowing the anchor and settling in the area. It is a nice place. But some of us get stuck here (bureaucratic SNAFUs notwithstanding) due to the Gulf Stream weather. As far as crossing the Stream under conditions that meet our criteria (Wind direction, Speed and Seas), this is the longest spate of unsuitable weather we can remember. The curve shows the average (from D-10 to D) of all forecast values predicted for a given day. The green bands are the good stuff. The weather has followed the wavy forecast curve almost slavishly — albeit with teases. At least it is good weather for waxing the deck, meeting even more of the nice folks here, and being stuck here meant being here for a potluck with excellent barbequed pork provided by the marina and cooked by the dockmaster — and a scad of yummy side dishes including Janet’s Spinach Balls.