Practical Weather – Nowcasting: let’s learn to read what’s around us at sea
THE PERFECT GIFT!
Give or treat yourself to a subscription to the print + digital Journal of Sailing and for only 69 euros a year you get the magazine at home plus read it on your PC, smartphone and tablet. With a sea of advantages.
Those who sail know: planning is essential, but the sea is alive and changes quickly. For this reason, real-time meteorology, so-called nowcasting, is an increasingly strategic tool in managing safety on board especially in the summer months when sailing for extended periods of time. Together with Meteomed meteorologist Riccardo Ravagnan, we have learned how to read synoptic charts, forecast models and alerts along the way; now the real breakthrough is knowing how to observe the atmosphere around us and its evolution while we are sailing.
What is nowcasting and why is it decisive
Nowcasting is not forecasting: it is real-time observation of what is happening. While models tell us what might happen, nowcasting shows us what is really happening, instant by instant. There are many main tools available, and we list the main ones.
Satellite images are useful for identifying cloud cover, convective systems, and their evolution; the use of weather radar or satellite composites, on the other hand, serve us to assess the intensity and vertical development of thunderstorm cells. Another tool to consider are lightning maps, which identify the presence, intensity, and displacement of thunderstorms.
Using these tools means “looking up at the sky,” but with the help of professional tools that are now accessible to recreational boaters.
Thunderstorms: much more than rain
Too often, storms at sea are underestimated. In reality, they are complex and potentially dangerous phenomena, capable of generating sudden wind gusts in excess of 40 knots, with sudden changes in direction, short, messy and difficult-to-manage seas, as well as visibility reduced to a few tens of meters. Monitoring an active thunderstorm on the lightning map makes it possible to understand its trajectory, estimate its evolution, and decide whether to alter one’s course or set anchor in the roadstead in advance.
A real-life case: between Elba and Capraia
While sailing between Elba and Capraia with quiet forecast from model, it happens that at 11:00 active lightning appears on the map between Gorgona and Corsica. Satellite images confirm a rapidly expanding cell to the northeast. Thanks to nowcasting, the commander decides to anticipate entering the roadstead and take cover. At 1:15 p.m., gusts of 42 knots hit the area and visibility plummeted below 300 meters. A timely and wise decision, made possible only by careful observation in real time.
Prevent, do not fear
The message is clear: nowcasting is not about creating alarmism, but about enhancing the commander’s awareness. Let’s keep this in mind: no forecast model can capture every detail, from micro-convictions to isolated cells. That’s why tools like Meteomed, which integrate radar, satellite imagery, and live lightning into a single platform, are a practical support to recreational boating.
What to learn to observe
While we are at sea, our eyes must constantly watch what is around us, and in particular we must keep an eye out for cumulonimbus, which are those towering clouds with vertical development, clear premonitory signs of obvious instability; special attention must also be paid to concentrated lightning, i.e., the indications of active and dangerous storm cells: we must immediately adjust our course to escape this danger. Having studied the forecast models before departure, however, any deviation from the forecast is a warning sign.
Federico Lanfranchi
Share:
Check out the latest issue
Are you already a subscriber?
Ultimi annunci
Our social
Sign up for our Newsletter
We give you a gift
Sailing, its stories, all boats, accessories. Sign up now for our free newsletter and receive the best news selected by the Sailing Newspaper editorial staff each week. Plus we give you one month of GdV digitally on PC, Tablet, Smartphone. Enter your email below, agree to the Privacy Policy and click the “sign me up” button. You will receive a code to activate your month of GdV for free!
You may also be interested in.
What are the doors used for in a sailboat?
Lele Panzeri, well-known advertising creative and inveterate sailor (by the way, he is organizing creative sailing courses for September and October on his boat), after explaining to you why, in his opinion, bow mooring is better than stern mooring, and
Practical guide for advanced boat owners: the guru’s tips for a long-sailing-proof boat
Sailor and nautical consultant Enrico Tettamanti explains how to optimize or choose your boat to make it safe, supremely comfortable, and seaworthy for long, very long voyages. He puts what he has learned in his 30 years of experience of
Make yourself a “holster,” and when you’re at anchor you stand like a king
Lele Panzeri, well-known advertising creative and inveterate sailor (by the way, he is organizing creative sailing courses for September and October on his boat), after explaining to you why, in his opinion, bow mooring is better than stern mooring, and
Sailors beware, Decathlon self-inflating life jacket recalled! Here’s what you need to do
Decathlon has issued a recall notice for Tribord’s self-inflating life jacket “LJ 150N harness gray/black” (part number 8801769). The company reported that under repeated stress, its inner tube could puncture, compromising the vest’s ability to inflate properly in emergency situations.
