Cold front effects coming Wednesday

Jan 02, 2018 News

Weather changes are on the way as a cold front makes its way into the Caribbean. The National Weather Service told Cayman 27 the fairly weak front is pushing into our area as early as Tuesday night (2 January) A low pressure system is also developing over the Bahamas, which is anticipated to somewhat strengthen the weaker primary front. "The winds presently are out of the North, about 10 to 15 knots, come tomorrow morning, they'll swing around to the northwest about 5 to 10 and then they'll gradually increase so by Wednesday (3 January) evening we will be looking at 15 to 20 knot winds," said NWS Meteorologist Avalon Porter. Public Education Topics - Cold fronts Although the Cayman Islands have a tropical marine climate, we are in a unique position to be far enough north to be affected by cold fronts during the winter months. Occasional surges of cooler air from the continental North America pushing far enough south into the western to northwestern Caribbean Sea. The leading edge of these surges is what you call a cold front. Cold fronts are normally associated with a high pressure system that lags just behind it. These systems are the major contributor to rainfall during the dry winter months. (Late October through early April) Most cold fronts do not produce a significant amount of rainfall but when alignments with winter Jet Streams can produce higher totals (See January 18 th 2003 – 9.45 ins). Stronger cold fronts along with its associated high pressure system tend to bring fresh to strong North to northwest winds and rough seas, especially along the Western and Northern Coasts of the Islands: Such fronts are locally called “Northwesters”. On average around 8 to 10 cold fronts with 3 to 4 being Northwesters pass through the Cayman Islands each winter. Impacts: The passage of these systems usually produce fresh to strong north to northeast winds and rough seas (May last up to a week for each system) which requires the National Weather Service to issue either Marine Advisories or Warnings depending upon its strength. A number of these systems may produce fresh to strong north to northwest winds and rough seas (May last for a few days), which requires the National Weather Service to issue the advisories or warnings but also alert the Port Authority and marines interests along the Seven Mile Beach. Definitions: Cold front - is defined as the transition zone where a cold air mass is replacing a warmer air mass. Cold fronts generally move from northwest to southeast. The air behind a cold front is noticeably colder and drier than the air ahead of it. Stationary Front- a boundary between warm and cold air masses that is moving very slowly or not at all. Frontal trough - An elongated area of relatively low pressure associated with a cold front that is usually associated with a shift in wind direction. These troughs may be pre-frontal, Post- frontal or induced depending on their location and how they formed. Artic High pressure system – These are cold air masses located behind cold fronts that form and adopt characteristics of their source region in the Artic. The cold front is the leading edge of this air mass.