Current conditions: It is 68 degrees F in Dakar, Senegal, with winds of 6 kts straight out of the North. Surface observations indicate that it is fairly humid with a dry air layer above the surface and then high clouds. Currently offshore west of Dakar, the wind is about 10 kts north-northeasterly increasing to 20 kts in the vicinity of the Cape Verde Islands. Seas are choppy with waves 1.5 to 2 meters.
Short-term forecast (in the next 24 hours): The temperature may warm up a few degrees (F) during the day but the marine influence will keep it pretty steady around upper 60’s at night and lower 70’s during the day. The high pressure system to the northwest will keep the wind directions pretty consistent over the next day (i.e., northerly at Dakar and northerly with a slight easterly component offshore). The waves will increase slightly to 2 to 3 meters.
Long-term (5 days): The high pressure system in the Atlantic is a quasi-persistent feature called the Azores High. It should remain in place for the next several days and lead to similar weather conditions to what we have described above. In three and half to four days the winds may become calmer offshore west and southwest of Dakar. Eventually a North Atlantic low pressure system will interact with the Azores High and may lead to changing conditions but that is several days off.
Forecasters Brown and Dixon
2 replies on “Steady Temperatures, High Clouds and Decreasing Winds”
‘Weather’ or not to launch? That is the question. After spending 6 hours the last 2 days with teachers and student teachers building toward the launch of the JRH it has become very apparent that, especially for those folks land locked in places like Alberta, Canada we need to explain a few things about the sea. First, I urge everyone to pick up a copy of Rowing to the Son, which is presently going through an incredible promotion of less than $10 through Kindle right now. Watch the video piece on Northwest.com related to The voyage: North Atlantic Rowing Race 2006 and pick up Markus’s DVD of the Salish Sea Expedition, or at least watch the trailer.
For translation purposes, one knot is equivalent to 1.15 mph or 1.85 km/h and 1 m equals 3.28 feet. So this translates, in the latest report, to 19–37 km per hour winds and 5 to 10 foot waves. On what is referred to as a Beaufort scale, we’re talking about best case scenario of force 4 to 5–looking at whitecaps and light spray. For those that have not been on the ocean or larger water bodies, you have to understand something about ways. They are produced by the friction created from the wind blowing over the surface of the water and they are largest when a strong wind has been blowing in the same direction for some time. Waves usually run roughly at right angles to the wind and will be really large when there is sufficient fetch (a distance of clear water over which the wind blows). They will normally be larger and steeper when the wind blows against, rather than with, the current or tidal stream. This is why monitoring currents is so important.
As a former naval officer (almost 4 decades ago), I always thought it was quite interesting filling in the duty officers’ log as I left the bridge. We filled in information as per what was required in terms of a system called the Beaufort scale. The Beaufort scale was developed in 1805 by Adm. Sir Francis Beaufort of the British Navy. It is a guideline for what can be expected in certain conditions and the weather class division system. It assumes open ocean conditions with unlimited fetch.
Maybe it was something passed down from the British to the Canadian Navy, but to me it always made the conditions that we were dealing seem so trivial. When you are serving on an Iroqouis class destroyer out of CFB Esquimalt which has a length of 129.8 meters (425.9 feet), a beam of 15.2 m [49.9 feet], a draft of 4.7 m [15.4 feet] with an average speed of 29 kn [53.7 km/h) and a range of 8303 km. and a complement of 280 sailors the kind of seas being described would be considered as smooth sailing. (For those that don’t know the Huron was the 1st Canadian warship to be operationally sunk in Canadian waters to serve as the beginnings of an incredible reef that divers visit stay). However, what does that look like for the crew of the JRH where the overall length is 29 feet [8.8 m] the beam is 6 feet [1.8 m] – are we beginning to understand the difference of scale here?
I really do hope you all will take advantage of the efforts provided by Dr. David Burch from the Star Path School of Navigation and all those contributing to keeping you up-to-date on the latest meteorological and ocean conditions (Angie & crew). Not only do we, but definitely the crew of JRH appreciate their efforts. Pray for the window…
Thanks to the AMS student forecasters – they have a tough job and demanding schedule to keep the guys aware of what’s coming weather-wise, and it’s very much appreciated! We’ll also be measuring what actually happens out there because, as we’ve all experienced, sometimes the forecast doesn’t always come to pass. And thanks to Rick, Jordan, and all others, trying to make what the oarsmen experience in various wind and sea conditions comprehensible to those who haven’t been out there. That’s a tough job too.
Unlike on land where most of us can escape bad weather in the shelter of a building, at sea there’s only the boat to seek shelter in and, no matter how big or small, it is always riding on the waves and being pushed around by the wind. You might guess, and correctly, that a boat’s reaction to waves is very dependent on its length versus that of the waves, and how the boat is pointed relative to the crest-line of the waves. Occasionally it pays to be in a shorter vessel on very long wave swells as the “ride” is more comfortable than if in very long ship in those same swells. And everybody reacts differently to long versus short wave-motions on a boat. For example, my grandfather could easily withstand the short, relatively sharp motions of a 10m (33′) boat in a Beaufort force 4-5 wind & sea, but on an ocean liner with long, slow pitch/roll motions in that same sea state, he’d get quite seasick. On land, one can experience something similar by driving a car on mountain roads with lots of tight curves – certain frequencies of whole-body accelerations are hard for our inner-ear (and brain) to cope with leading to “car” sickness. And it’s not always a reaction while at sea that’s hard to cope with, but sometimes when you get off the boat – known as ‘land-sickness’ – which is my problem. After being on the water for even a day on a boat moving in almost any sort of waves, I often feel like the room is moving when sitting at home. We’ll see if any of the guys feel that way when they get to Miami – 60-90 days is a long time to be out on the waves. May they have fair seas and a following wind!