The Great Southern Route : 2010 - 2011
WEATHER ROUTING 248 | GSR During the remainder of the year (May through November), our attention turns toward the tropics. Tropical cyclone season begins on 15 May, and on average, we will find tropical cyclone development occurring in May about once every other year across this region. Development typically reaches its peak in late July and August, with cyclone frequency rapidly diminishing in September, October, and November (tropical cyclone season concludes on 30 November). Tropical cyclone development is most likely to occur off the Central American coast (south of 15N) and across adjacent offshore waters. Typical tracks will be toward the West or West- Northwest, offshore from the Central American coast, weakening as they move into cooler waters near and west of 110W. However, an alternate track is one that will often take tropical cyclones on a more northwestward track, moving in the general direction of the Baja Peninsula and the Sea of Cortez. This is more likely to occur from mid/late August onward, as large troughs of low pressure in the mid and upper levels of the atmosphere more eastward toward the Baja Peninsula. Increasing SE-S-SW winds aloft in advance of these troughs will act to "pick up" and "recur ve" tropical cyclones toward the northwest and north. Aside from the tropics, strong NW-NE-E wind surges are less common or uncommon along the Central American coast and the Gulf of Tehuantepec, as large cold high pressure ridges farther north decrease in frequency. Along Central America, NE-E winds are still in place, but tend to be lighter, normally no more than force 5-6, and tending to occur mainly across gaps in coastal ranges as well as across the Gulfs of Papagayo, Dulce, Nicoya, and Fonseca. This occurs as high pressure builds westward into the Western Caribbean and toward Central America. NE-E combined seas are generally no more than 3-6 feet, tending lower closer to the coast. E-SE-S winds are most dominant across the Gulf of Tehuantepec and "light", with wind speeds generally on the order of force 3-5 and combined seas generally E-SE-S in direction, Farther north, across the Gulf of Tehuantepec, favored directions in wind surges are NW-N-NE, with N-NE winds in the western gulf, and NW-N winds further east. This occurs as northerly winds across inland valleys "fan out" across the gulf itself. Gale force winds are common in these surges, with severe surges in some cases bringing storm to hurricane force winds! Seas as high as 12-15ft can occur during wind surges (even as high as 20 feet in severe surges) across the mouth of the Gulf, with much lower seas found along immediate coastal waters. The weather turns more benign as we look farther north across the Mexican Riviera. Winds here are generally in the form of lighter W-NW-N winds, speeds generally not exceeding force 4-5. In fact, along immediate coastal waters (within approximately 2-3 miles from shore), and in cloud/ rain free areas, winds will show a tendency toward onshore sea breezes during the day (generally occurring the period from mid morning through late afternoon), with offshore breezes at night and during the early morning hours. Combined seas will generally be from W-NW-N and long-period, heights generally no more than 6-7 feet, though larger long-period sets can occur, from surges of higher NW-N winds farther north. Across the Sea of Cortez, general wind directions are NW-N and tend to be light, with speeds generally no more than force 4-5. However, the passage of cold fronts north of the area and arrival of high pressure building in from the west will bring higher NW-N winds, with speeds approaching if not reaching minimal gale force, typically as high as force 7-8. NW combined seas during these wind surges will often reach as high as 10ft with locally higher sets, particularly along the southwestern coast of the Baja Peninsula. NW winds will generally "wrap around" the southern tip of the Baja Peninsula and become WSW-W, and during wind surges can reach near gale to gale force (force 7-8). However, with a more limited fetch in place, combined seas will generally tend to consist of a wind chop, typically no more than 4-6 feet across the region. WHAT ELSE COMES to mind? How about tropical cyclones, adverse weather from trade wind surges, and even the effects from cold fronts? Maybe some of these things come to mind as well, but truth be told, mariners and vacationers alike should be aware of these weather concerns (and others) when traveling in this part of the world, so we'll revisit this rather expansive area, and give a bit of a "refresher" if you will about the weather dangers to consider and what to look for in this part of the globe. Even the most experienced mariner must be wary of the potential weather dangers along the way.... without question this is one of the most important considerations (if not the most important) for trip planning. Obviously, given the rather large coverage area involved, there are a wide variety of weather patterns and phenomena to consider. We will educate the reader on the best times of years to travel and the best course(s) of action to take to avoid (or at least minimize) exposure to adverse weather and make for an enjoyable time for all on board. Finally, we will explain the importance of utilizing weather providers as guidance for planning and routing. CENTRAL AMERICAN COAST TO THE BAJA PENINSULA: The period from November through April is known for significant surges of higher winds/seas across this region. These occur about every three to four days, occurring as large, cold high pressure ridges move east to southeastward and north of the area, across the Gulf of Mexico and into the Northern Caribbean. Wind surges are normally in the form of N-NE-E winds across the Central America, where winds can reach as high as gale force (force 8-9), especially across gaps in coastal ranges and across the Gulfs of Papagayo, Dulce, Nicoya, and Fonseca. Similar higher wind surges can occur in NE-E winds along the south side of the Peninsula de Azuero, found between Punta Mala and Punta Mariato. Large seas, as high as 10-12 feet, can also occur during these wind surges, particularly across more offshore waters, where N-NE-E "fetch" is greater. Weather Patterns and Routing: The Tropical and South Pacific By: David Cannon, Jeremy Davis, and Garrett Gwiazda Weather Routing Inc. So here we are again in the Tropical and South Pacific, where relaxing, peace, and tranquility are commonplace, where sunshine and palm trees are everywhere. These are the things that always come to mind when one thinks of what it's like to be in this part of the world...
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