Friday, May 27, 2016

Bermuda to Ireland Weather Forecast - Locus Weather

As Bill has mentioned a few times in his posts, we have been utilizing the services of Ken McKinley at Locus Weather for the last 11 years for all our major passages.  Ken was a familiar voice doing local weather forecasts on radio when I was growing up in Midcoast Maine so I still read his messages in his voice in my head.  He can't come more recommended for anyone planning a passage as we are regularly amazed at his accuracy, and his attention to detail and personal attention take a lot of the stress out of passage planning.  I hope he doesn't mind me posting his forecast gives readers an idea of what the boat will be facing and gives real insight into the sort of decision-making that goes into weather routing and passage planning aboard Visions of Johanna. -- I have added some weather fax charts from NOAA to help visualize what Ken is describing in his text....any errors in matching his descriptions to the images are of course mine.

Google map screen capture for BDA Departure to Botany Bay Ireland
Great Circle Route is the thin Black Line.  Note how it extends north of the RED Iceberg Limits (see actual Ice Map below).  Green line with Green Diamond Waypoints are Ken's proposed routing taking into account Gulf Stream, Expected Weather, and keeping well south of the Iceberg limit.

To: Yacht Visions of Johanna, Bill Strassberg

From: Ken McKinley, Locus Weather,

Forecast for yacht trip from Bermuda To Bantry Bay, Ireland

Desired Departure Date: Sat 28-May-16, 1200 GMT

Date and Time Prepared: 1915 GMT Fri 27-May-16

Average Speed of Yacht: 7.5 knots

Weather Factors:

At 1200 GMT Friday: Low pressure was centered in western Quebec southeast of James Bay with a warm front extending south-southeast to Cape Cod, then east-southeast to about 37N/60W. A ridge of high pressure extended from North Carolina east to the north of Bermuda, then east-southeast to about 32N/50W. Low pressure of subtropical origin was centered northeast of the Bahamas near 28N/63W.

The low northeast of the Bahamas will likely evolve into a subtropical or tropical storm later today or tonight and will move slowly northwest through the weekend, reaching the South Carolina coast later in the weekend. A high center will develop in the ridge northeast of Bermuda later today and will remain nearly stationary near 35N/63W through tomorrow and into Sunday, then will shift slightly west and weaken a bit later Sunday. The low in eastern Canada will move east today and this evening, then southeast to the Gulf of St. Lawrence later tonight. The low will become better organized later tomorrow as it moves southeast to the south of Newfoundland, then will strengthen later in the weekend as it continues southeast. By Sunday evening it will be centered near 43N/45W with a cold front extending southwest to about 37N/50W, then west-northwest to about 38N60W. High pressure will build north of the front over Nova Scotia coast Sunday afternoon and move east off the coast by evening.

The low will continue to intensify through Sunday night and Monday while moving slowly east-southeast, passing through 40N/40W later Monday. The portion of its front west of 50W will push south through this period, but also become weaker, and will extend from about 29N/50W to about 36N/60W by Monday evening. The high to its north will become a bit stronger and move east to about 43N/53W by Monday evening while the high to it south (northeast of Bermuda) remains in place but weakens. The western portion of the front will dissipate through Monday night and the Bermuda high will be absorbed into the circulation of the stronger high to the northeast, which will be centered near 36N/53W by Tuesday morning with a ridge extending east to the north of Bermuda. The high will then settle slowly south through the second half of the week while another low makes its way east through eastern Canada, moving east of southeastern Newfoundland on Wednesday, then becomes a bit disorganized while moving east-southeast through Wednesday night and Thursday before becoming stronger again near 43N/40W during Friday. A cold front extending west-southwest form the low will push south of 40N between 50W and 65W Thursday morning  and will have pushed south to 32N by Friday. High pressure will build over Atlantic Canada on Friday and will be centered over Nova Scotia by evening. 

There is a chance that a low may develop south of Bermuda late next week and then move east-northeast during the following weekend, but it now appears that if this system develops it will not be that strong and will remain south of 30N.

In the extended range, then low in the central Atlantic will become stronger through the following weekend and accelerate to the northeast, likely reaching about 50N/28W by late Sunday. It will then turn more to the north early in the subsequent week. This system will have  large circulation through this period, dominating the Atlantic north of 38N and east of 52W.


Winds will be rather light for a departure tomorrow, and will remain light through  the rest of the weekend as the yacht moves across the high northeast of Bermuda. The yacht will then cross the weak frontal boundary late Sunday night leading to a wind shift from NW to SE, but wind speeds will still be very light, and the front is not likely to be very active. As the high moves southeast early next week and the yacht moves northeast, winds will veer through S to SW, and wind speeds will increase as the low moves east to the north of the route with seas building as well. Winds will veer more toward the W through the middle of the week, then will shift to NW later Thursday as the cold front drops across the route.

As the low intensifies toward the end of the week, winds will become quite a bit stronger and back a bit toward WNW. Near gale force winds will be possible from later Friday into Saturday as the yacht nears 40W, but as the weekend progresses, the low will move northeast faster than the SOA of the yacht, thus allowing winds to slowly ease.

I have attached 3 updated altimetry charts, for similar areas as were sent the other day: one from Bermuda north and east showing the Gulf Stream out to almost 45W, another zoomed in a bit showing the stream in more detail between about 63W and 50W, and yet another showing the currents farther east in the central Atlantic from about 38N northward.

Gulf Stream Altimetry charts sent by Locus Weather

I have also attached the latest chart from the North American Ice Service showing the extent of iceberg coverage.

Ice Chart -- This magenta line has been replicated in the google maps chart above so you can see how the ice area affects the route chosen

It does not appear to be worthwhile to deviate westward to enter the Gulf Stream farther west, as was suggested a couple of days ago. Rather, heading generally along a great circle toward Bantry Bay until reaching the Gulf Stream will work well. Some motoring will be needed due to light winds, but this will be inevitable no matter which route is chosen. Once reaching the stream, riding it generally east for a few days appears to be a good choice as continuing along the great circle route would bring the yacht too close to the ice for comfort. Also, with the intensifying low in the central Atlantic later next week, moving farther north earlier would place the yacht into strong northerly winds earlier with high seas, and would also lead to NE winds during the following weekend. In other words, a long period of moderately strong (perhaps gale at times) headwinds with rough seas.

With all of this in mind, the following waypoints are suggested:

Thence parallel sailing until low pulls away allowing GC toward Ireland

-- This route is shown above on google maps to help visualize.  The Dip SE is to help with sailing angle in expected wind and presumably to follow the gulf stream a bit without getting too close to the ice region.

The forecast is shown for a departure tomorrow morning using the route shown above.


Time: Saturday morning 5/28/2016 (1200 GMT, 0900 ADT)
Expected approximate position: Departing Bermuda
Forecast Winds: ESE 11-15 kts.
Forecast Sea State: 2-3 ft.
Comments: Partly cloudy. Winds veering to SE through the day and becoming lighter.

Time: Saturday evening 5/28/2016 (0000 GMT Sunday, 2100 ADT)
Expected approximate position: 33.5N/63.5W
Forecast Winds: SE 8-12 kts.
Forecast Sea State: 1-3 ft
Comments: Fair weather. Winds becoming light and variable overnight.

Time: Sunday morning 5/29/2016 (1200 GMT, 0900 ADT)
Expected approximate position: 34.6N/62.1W
Forecast Winds: Light and variable.
Forecast Sea State: 1-2 ft.
Comments: Fair weather. Winds becoming NW by afternoon, still light

Time: Sunday evening 5/29/2016 (0000 GMT Monday, 2100 ADT)
Expected approximate position: 35.8N/60.7W
Forecast Winds: NW 7-10 kts.
Forecast Sea State: 1-2 ft
Comments: Fair weather in the evening, more clouds later at night, perhaps a shower. Winds shifting to SE late at night. 

Time: Monday morning 5/30/2016 (1200 GMT, 0900 ADT)
Expected approximate position: 36.9N/59.4W
Forecast Winds: SE 9-13 kts.
Forecast Sea State: 2-4 ft.
Comments: Variable clouds, chance of a shower in the morning, clouds decreasing in the afternoon. Winds veering to S and increasing through the day.

Time: Monday evening 5/30/2016 (0000 GMT Tuesday, 2100 ADT)
Expected approximate position: 38.0N/58.0W
Forecast Winds: S 12-16 kts.
Forecast Sea State: 3-5 ft
Comments: Partly cloudy. Winds veering to SW and increasing overnight, seas building.

Time: Tuesday morning 5/31/2016 (1200 GMT, 0900 ADT)
Expected approximate position: 38.8N/56.3W
Forecast Winds: SW 16-20 kts.
Forecast Sea State: 5-8 ft.
Comments: Partly cloudy. Winds a bit stronger, seas a bit higher through the day.

Time: Tuesday evening 5/31/2016 (0000 GMT Wednesday, 2100 ADT)
Expected approximate position: 39.6N/54.7W
Forecast Winds: SW 19-23 kts.
Forecast Sea State: 6-9 ft
Comments: Partly cloudy. Winds veering to WSW overnight.

Time: Wednesday morning 6/1/2016 (1200 GMT, 0900 ADT)
Expected approximate position: 40.2N/52.8W
Forecast Winds: WSW 19-23 kts.
Forecast Sea State: 6-8 ft
Comments: Variable clouds, a passing shower possible. Winds veering to W by afternoon.

Time: Wednesday evening 6/1/2016 (0000 GMT Tuesday, 2100 ADT)
Expected approximate position: 39.8N/50.7W
Forecast Winds: W 19-23 kts
Forecast Sea State: 6-8 ft
Comments: Mostly cloudy, a few showers at times.

Time: Thursday morning 6/2/2016 (1200 GMT, 0900 ADT)
Expected approximate position: 39.5N/48.7W
Forecast Winds: W 19-23 kts.
Forecast Sea State: 6-8 ft.
Comments: Mostly cloudy with occasional showers. Winds shifting to NW by afternoon, a bit lighter.

Time: Thursday evening 6/2/2016 (0000 GMT Friday, 2100 ADT)
Expected approximate position: 39.5N/46.9W
Forecast Winds: NW 14-18 kts
Forecast Sea State: 6-8 ft.
Comments: Variable clouds, a few showers in the area.

Time: Friday morning 6/3/2016 (1200 GMT, 0900 ADT)
Expected approximate position: 39.5N/45.1W
Forecast Winds: NW 14-18 kts.
Forecast Sea State: 6-8 ft.
Comments: Variable clouds, scattered showers. Winds backing to WNW and increasing through the day, seas building.

Time: Friday evening 6/3/2016 (0000 GMT Saturday, 2100 ADT)
Expected approximate position: 39.5N/43.3W
Forecast Winds: WNW 26-30 kts.
Forecast Sea State: 9-13 ft
Comments: Variable clouds, periods of rain or showers. Winds backing to W overnight, speeds remaining about the same, little change in seas.

Winds and seas slowly easing through the weekend of 6/4-5 as the yacht moves north of 40N and east of 40W, significant westerly component in the wind direction.

NOTE: Positions given above are not necessarily intended to be waypoints, but rather just a general location for purposes of providing weather conditions in that area. These positions should not be used for navigation.


Recommendation is to depart as planned tomorrow morning, and to follow the route shown above.

Some modifications to the route may become possible later next week depending on the progress of the yacht and the details of the developing low. If the low is stronger and/or moves more slowly, then it may be necessary to slow down a bit, on the other hand if the low moves more quickly, then the yacht may be able to pick up a great circle route earlier.

Delaying departure until Sunday might actually lead to more difficult conditions late next week as the yacht would be farther west when the low intensifies and in a region where the pressure gradient would be stronger with stronger more northerly winds and higher seas. On the other hand, the low would be pulling away more quickly, and this might allow an earlier turn toward the north. 

In general, a departure tomorrow will lead to reasonable conditions for the first several days of the passage, and will keep options open for adjustments later next week if needed. Waiting until Sunday would be acceptable - not dramtically better or worse than a Saturday departure.

Call or email with any questions.

Gram again here -- Forecast looks pretty good really.  A bit of motoring early to keep on track is certainly acceptable.  The stronger wind tends to be from behind or at least on the beam so hopefully upwind slogging will be minimized.  As Bill mentioned to me on the phone the other can't really expect to cross the northern atlantic without seeing a gale (34-47 kts wind) -- you just want to avoid the storms (48+ kts)  and not get plastered.  When I crossed the atlantic on a ship for School in 2000 in January we saw something like 7 storms and 3 gales over 18 days and I certainly wouldn't have wanted to be out there in anything smaller than the 300+ foot ship I was on, but that is why you sail to Ireland in June and not January.

No comments: