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How to better judge a weather forecast's accuracy

by Bermuda Race 31 Jan 07:00 PST
Racers get underway at the start of the 2016 Newport Bermuda Race © Barry Pickthall / PPL

Veteran race navigator and oceanographer Frank Bohlen looks back to the 2016 Newport Bermuda Race and points to free resources from the Cruising Club of America for those interested in improving their ability to evaluate a forecast.

Of the many challenges facing the Newport Bermuda racer, none is more critical than the weather. An understanding of the factors governing the probable wind speeds and directions and their evolution during the Race or on the return is essential to strategic planning and a safe passage.

This understanding must go beyond simple acquisition of weather forecasts from the variety of public sources or contract weather services, since the turbulent and sometimes chaotic nature of weather often affects forecast accuracy. This fact was made particularly clear during the 2016 Newport Bermuda Race.

Before the skippers meeting that year, both the European and U.S. weather models forecasted conditions favoring the development and progression of a series of low-pressure systems expected to move offshore to the south of Cape Hatteras immediately preceding the start time of the Race. By the time the meeting was held, the night before the scheduled start, refined forecasts had an energetic low moving over North Carolina on the day of the start. The forecast called for this low to move steadily offshore, progressively intensify over the warm Gulf Stream waters, and subsequently track to the north and east across the Newport Bermuda rhumb line. The prospect of very rough seas resulting from gale- to near-gale-force northeasterly winds acting against Gulf Stream currents raised concerns through the fleet and prompted the Race Committee to consider postponement. Ultimately, the Race started as scheduled but more than one third of the fleet withdrew, including all 7 boats in the Gibbs Hill Lighthouse Division.

Why Forecasts are Challenging

Weather is the current state of the atmosphere, describing, for example, the degree to which it is hot or cold, wet or dry, calm or stormy.

Weather is dynamic, displaying significant spatial and temporal variability due to variations in latitude, surface character and roughness, atmospheric water content, and incoming solar radiation

The resulting flows are turbulent, meaning they are to some extent chaotic, and best described by statistical methods, e.g. probabilities. Yet most forecasts are taken to be absolute.

In addition to knowledge of atmospheric physics, forecasts depend on a combination of observational data, analyst interpretations, and numerical models. Accuracy depends on the adequacy of each component.

In contrast to forecast conditions, however, the majority of the fleet had a pleasant sail to Bermuda with wind speeds seldom in excess of 20 knots. The forecast low did form, but it moved more rapidly than forecast across the rhumbline resulting in only the fastest boats experiencing a period of high wind speeds and rough seas as they passed through the Stream on Saturday. As might be imagined, the differences between the forecast and the encountered conditions were the subject of much post-race discussion.

Central to these discussions was an understanding of just what a weather forecast is and is not. In particular, the extent to which a forecast is an estimate of the probability of what may happen rather than an accurate specification of what will happen. This is a complex subject that is continuously evolving. While an amateur cannot be expected to completely understand all the processes governing the circulation of the atmosphere, and the observational methods and the techniques used to model and ultimately forecast probable conditions, it is possible for an interested individual to gain sufficient understanding to permit personal evaluation of the probable accuracy of a given forecast. Adding to this his or her direct onboard observations of actual wind and sea-state conditions as well as ship's barometer readings and the associated trends can significantly improve forecast accuracy.

To help mariners increase their personal ability to evaluate weather conditions and the associated weather forecasts, the Cruising Club of America (CCA) initiated a series of Marine Weather and Sea State symposia, the first in February 2018 in Maryland and the second in February 2020 in Seattle, Washington. The presentations from each were recorded and are available on the CCA website under the Safety and Seamanship tab at Online Weather Seminar or via the CCA YouTube channel.

Safety gear training videos launched by official Bermuda Race sponsor

Learning to manage personal AIS and inflatable PFDs is the initial focus of Life Raft + Survival Equipment YouTube Series.

Safety has always been a top priority for the Newport Bermuda Race and its long-time partner and new official sponsor, Life Raft + Survival Equipment. LRSE has provided service and training support to competitors since the 1980s and more recently has been doing so in the form of equipment servicing, retail, and safety training by Brian Flowers through pre-race Safety at Sea Courses.

For 2022, LRSE has stepped up its commitment by creating video content to train more crews in the proper use of safety equipment, response to an emergency situation, and general information about dates and deadlines that competitors must know in order to meet the safety requirements of the Newport Bermuda Race.

AIS is now a requirement, as detailed in the Newport Bermuda Notice of Race. Flowers, VP of Operations at LRSE, says of AIS, "This is one of the most exciting products—I have waited a long time for a person-overboard, transmitting device that tells the vessel where the person overboard is located. With the growing popularity of AIS receivers, a device now exists thatwill talk to the vessel from a person in the water as long as the vessel has an AIS receiver. This technology is life changing."

Located in Tiverton, R.I., just a short drive from Newport, LRSE has answered the call to be the go-to local retailer of life rafts, PFDs, AISs, EPIRBs, and all other maritime safety equipment. Along with selling the equipment, LRSE also inspects and delivers. For this race season LRSE has asked that competitors make accommodations for their necessary equipment by tax day, April 15th, so there's enough time to deal with extenuating circumstances and ensure required equipment is received by race day.

Due to the current supply chain issues felt by industries across the globe, it is important that all competitors pay close attention to this vital information. Failure to meet these deadlines could prevent competitors from obtaining the necessary equipment to meet the minimum requirements.

We asked Jim O'Connor, President of Life Raft and Survival Equipment, why they've stepped up their support of the event. He said, "Our name says it all in what we do and who we are. Having that name as an Official Sponsor of the race is a constant reminder that we're serious about safety and that safety is first in this race."

In acknowledging LRSE for their sponsorship, Mark Lenci, Vice Chairman of the 2022 Newport Bermuda Race said, "LRSE is the safety and equipment vendor in New England. They're long-time collaborators with us in the Cruising Club of America's Safety at Sea program. Not only do they have a display of the all the latest SaS equipment at all of our courses, they service our life rafts, provide all our flares (at no charge), provide their life jacket service expert for an hour long session at each course (at no charge), and have developed a live demo of the AIS/DSC MOB beacons with a chart plotter, VHF radio, life jacket, and AIS/MOB device. They inflate the lifejacket and show how the whole system actually works. It's super helpful."

For more information or help meeting the race's requirements, call 401-816-5400 or visit LRSE AIS and other safety training videos can be found on the Bermuda Race playlist and on LSRE's Youtube channel.

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