A voyage from the northeast United States to England, across the northern Atlantic, often referred to as a jump across the Pond, is not too great in physical distance-3000 miles-but does entail dealing with three worthy elements: fog, ice, and low-pressure systems.
These features, often discourage passagemakers from taking a northern route, in favor of a southern Bermuda-Azores-England route. A southern route has none of the features mentioned above but is substantially longer, by 800 miles, and often accompanied by light or calm wind conditions.
A southern route is appropriate for boats heading to the Mediterranean but is not preferred for those heading to England, or points north, since it consumes more travel time and traverses heavily trafficked shipping routes found around the Englsih Channel.
For those who want to make the British Isles in a timely manner, and in doing so have time to cruise these waters in August and September then the northern route is preferred.
Fog, ice, and low pressure systems along a northern route can be made manageable with a little research and preparation. Fog occurs mostly south of Newfoundland, where warm Gulf Stream water and air collide with cold Labrador Current. Cooling is rapid and dewpoint levels are easily reached producing thick fog that endures.
Fog by itself is not too difficult to negotiate, if a boat is equipped with a good radar, but fog near Newfoundland is also accompanied by ice, fishing vessels, and a continuous stream of large commercial vessels plying great circle routes connecting Europe and the US.
Dealing with fog and ice begins with an examination of ice charts and broadcasts produced by the International Ice Patrol. These charts and bulletins are available over SSB broadcast frequencies and the INMARSAT- C SafetyNet service.
Ice bulletins (text only) are broadcast at 0000Z and 1200Z daily during ice season, which normally runs from February to August each year, primarily by US Coast Guard Communications Station Boston, MA (NMF/NIK) and Canadian Coast Guard Radio Station St. Johns Newfoundland (VON).
Ice bulletins are also broadcast by secondary stations including: METOC Halifax, Nova Scotia (CFH), Canadian Coast Guard Radio station Halifax (VCS), Radio Station Bracknell, UK (GFE), and US Navy Norfolk VA (NAM) and Key West FL.
A daily facsimile chart, graphically depicting limits of all known ice, is prepared and broadcast at 1600Z and 1810Z daily. This facsimile chart is also placed on COMSATs INMARSAT-A FAXMAIL Server.
Ice concentration is greatest in April, with the most southern ice limit occurring in May. Records show median ice limit at the Tail of the Grand Bank (42-20N), but ice has extended as far south as 38-30N (1990). Eastern limit of ice is near Flemish Cap, a bank near 47N/45W.
A very interesting aspect of tracking icebergs is that approximately half of the icebergs found near the limit of all known ice (LAKI) were previously undetected. For this to occur icebergs had to have slipped by the various detection means (ships, aircraft, satellite imagery), or have been created in the LAKI region.
A most likely answer to this phenomena is that icebergs split into two or more pieces as they approach warm water near the southern extent of LAKI, and this splitting is most likely a part of the melting process. Though this splitting theory has not been confirmed it does indicate there are many undetected icebergs and a sailboats track line should stay south of the LAKI.
July and August are the best months for a North Atlantic transit, as the number of icebergs is at a minimum. Statistics from the International Ice Patrol for the 1995 ice season give a feel for the amount of ice traveling south. In April 1995 there were 334 icebergs spotted south of 48 degrees N, in May 405 bergs crossed the 48N parallel heading south. June had 218 bergs south of 48N, and in July there were 39 bergs spotted south of 48N. There were no significant sightings in August, and in general, most ice was found north of 41N, between 45W and 55W.
North Atlantic Weather
Weather systems across the North Atlantic are influenced by the interaction of the northern edge of the Bermuda-Azores high pressure system and semi-permanent area of low pressure sitting near 60N.
Coming off the top of the Bermuda-Azores high are west and southwest winds carrying moisture, and when these winds mix with cold and dry air from polar regions formation of low pressure systems is possible.
Great circle tracklines leading from the US to England cross this area of convergence and so low pressure systems are a possibility throughout the year. However, lows forming during summer months are milder than winter lows since such a sharp contrast in air temperature and moisture content does not exist.
For lows to form an upper level trough needs to exist in the polar jet stream and a good way to monitor formation and movement of these troughs is through use of upper air 500 mb charts prepared by the National Weather Service and broadcast by the US Coast Guard from Marshfield MA.
A feature on each 500 mb chart is a highlighted storm track, which indicates the most likely path of low pressure systems. If a boat stays south of this track, represented on 500 mb charts by the 5640 height contour, there is little likelihood of encountering Gale force winds.
If a 500 mb analysis and forecast chart is reviewed each day of a passage a boats track can be adjusted to stay near the great circle route, but south of the 5640 line. In this way Gales and unpleasant condtions can mostly be avoided, or at least anticipated.
During July and August the 5640 line undulates between 50N and 60N with troughs migrating west to east, alternating with ridges. Often a strong blocking ridge will remain stationary over Atlantic waters allowing a surface high pressure system (1030 mb central pressure or greater) to build, providing a week or more of pleasant weather. And on the other hand a series of upper level troughs can aid formation of surface lows which may give a voyage easterly winds and rain.
An un-modified great circle track across the north Atlantic to Ireland takes a boat up to 54N, and so positions it directly under the polar jet streams influence, which as mentioned above moves between 50N and 60N during summer months. Therefore a modified great circle which keeps a boat nearer to 50N, and use of 500 mb chart storm track data should do much towards lessening exposure to gales and storms.
Additionally, when winds blows against, or across the Gulf Stream, rough conditions can occur, so it is vital to monitor surface and aloft weather features and modify a base track to obtain both the best wind and current conditions.
Remember also that warm and cold eddies, north and south of main Gulf Stream flow, can assist in producing localized unsettled weather that may not appear on synoptic weather charts. In particular, warm eddies can cause local areas of fog, rain and gusty winds. Coast Guard weather facsimile broadcasts include a wind/wave chart which is extremely useful in evaluating present and future sea conditions.
In addition to weather concerns there is also significant commercial shipping traffic that must be monitored. Commercial vessels rigorously adhere to great circle tracks, as this is the shortest distance between two points in high latitudes, and so a trackline between St Johns Newfoundland and Ireland is well traveled.
Commercial traffic includes a variety of vessels; tankers, freightships (often called OBOs-for oil/bulk/ore), tugs with tows, oil rigs, military, fishing, and oceanographic vessels, and submarines. A thorough and good working knowledge of COLREGS is a must, and an understanding that rule of gross tonnage has substantial validity.
Though a complete review of COLREGS is not possible in this article remember that oil rigs being towed require a berth of 500 meters (1650 ft) and that tow cables connecting oil rigs to tugs are often submerged just below the surface and so great caution should be exercised when near these vessels, and you should not cross between a tug and tow.
Once a longitude of 15W is reached British Broadcasting Corporation (BBC) weather reports can be received and these will often provide current local and regional conditions and forecasts. As the British Isles are neared traffic separation lanes (TSL) begin to appear on coastal charts and these lanes need to be respected.
Once again, commercial vessels are required to follow these lanes, and small craft-such as sailboats-are cautioned to remain outside or when crossing to do so at right angles to minimize time spent within a lane.
Obtaining regional coast pilots for England before departing the United States and ensuring you are equipped to receive and transmit on VHF channels required for these traffic lanes is important. Much confusion and possible close calls can be eliminated by checking into these systems and communicating with approaching commercial traffic. I also cannot overemphasize the need to display proper running lights when operating at night.
Europe operates on the cardinal buoyage system, which is substantially different from the Unites States lateral system of buoyage. Most significant in British waters is that Green-Right-Returning is the rule, not Red-Right- Returning. In the cardinal system buoys are placed and designated in relation to the hazard they mark. This is different from the lateral system where buoys are placed to mark channels.
For example; a lighted buoy placed north of a dangerous rock will show a quick or very quick uninterrupted light, where as if it was to the east of this rock it would show three flashes in a group, if to the south six flashes in a group followed by a long flash, and if to the west nine flashes in a group. Buoyage systems are well explained in both Chart No.1 (Nautical Chart: Abbreviations and Terms, published by NOAA, DMA stock # WOBZC1) and The American Practical Navigator: an epitome of navigation, 1995 edition, published by DMA, stock #NVPUB9V1.
British Isles during the summer experience winds from the south through west, and in the range of Beaufort Force 3 to 8. Gales are reported only 1 to 3 days in June and July, and in May and August gales exceed 3% only in areas west of 15W.
Winds along the southwest coast are driven by the Bermuda-Azores high pressure system and as such often carry sufficient moisture to bring fog as they cool over North Atlantic waters. Fog sufficient to reduce visibility to less than a mile occurs up to 5% of each month from June through September.
Though fog may make landfall difficult visually the predominately rock and cliff coastline of Ireland produces a strong and easily identified radar image. Oil platforms are also regular features off Englands coast which makes a good reason to be equipped with radar.
Currents offshore are minimal, usually a knot or less, but as the coast is neared currents are felt running parallel to the land at rates between 1 and 3 knots, depending on wind and topography.
There are numerous beautiful and well protected harbors along Irelands coast suitable for landfall, which are too numerous to detail here, but are well described in cruising guides, and DMA Pub 142. In clear conditions making landfall is spectacular, and not too difficult in reduced visibility if proper charts, tide tables and buoyage have been studied.
A real challenge arises after landfall and clearing customs; where to have that first mug of Guinness!
|The Following User Says Thank You to Michael Carr For This Useful Post:||
ChrisHartnett (4 Weeks Ago)
|Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)|