Island Chain Land And Ocean Effects

   Images Courtesy NASA

The Florida Keys island chain and its surrounding bodies of water affects its local weather in a particular way. For example, if we examine the geographical location of this archipelago compared to the Bahamian archipelago we can see a clear distinct geographical position of the Florida Keys island chain to the Bahamian island chain in that the archipelago of the Florida Keys lie on a semi latitudinal northeast to west-southwest position to the Bahamian archipelago that lie on a semi latitudinal northwest to southeast position. Keeping this in mind we can now examine the uniqueness that the Florida Keys weather has compared to the Bahamas. During winter, cold fronts push through the island chain advecting cooler air latitudinally over the Keys, causing temperatures to dip into the 50's and 60's and even sometimes into the 40's. As this cold air mass passes over the relatively warmer water that surrounds the chain of islands it becomes modified and increases the air temperature by at least 5 to 8 degrees warmer across the middle and lower keys compared to the South Florida mainland low temperatures. A shallow layer of stratocumulus clouds always tend to develop when a cold air mass passes over a relatively warmer surface in which the ocean is, therefore it holds a larger quantity of heat and is not affected by radiational cooling effects as the land is, meanwhile this stratocumulus deck that forms passes over the lower and middle keys and also helps contribute in keeping the air temperature a few degrees warmer than the coastal Miami mainland low temperatures in which their air temperature would not be influenced by the ocean or the stratocumulus deck because the cold air advection there would be coming from a north-northwest direction from mainland Florida.

    Images Courtesy NASA

The upper keys are usually not influenced by its surrounding waters to modify it's air temperature in these cold air outbreaks as the trajectory of the cold air advection is more aligned on a north-northwest position which limits the amount of coverage that the cold air mass passes over the surrounding waters of the upper keys therefore the temperature difference there is generally 1 to 3 degrees warmer compared to mainland Miami Dade coastal minimum temperatures. Considering that the same type of cold air mass that passes through the Florida Keys also passes through the western most Bahamas we would have a larger gradient of air temperatures between the Keys and the Bahamas for just two reasons. First, being that there is a larger amount of water between Florida and the northwestern Bahamian islands than from mainland South Florida to Key West therefore the cold air mass would traverse over a greater distance of water leading to a greater modification of the cold air mass on a same general latitudinal location of those two archipelagos. Finally, the last reason is the longitudinal effect of the cold air mass losing its cold dry air characteristics by becoming modified substantially as it traverses southeastward over the tropical maritime waters of the Atlantic Ocean and over the Bahamian chain of islands. Now let's observe the land effects of the Florida Keys upon its local weather during late spring and summer. A common daily weather phenomenon during this time of the year effects Keys weather, the so called "Cloud Lines" which form over the island chain during the early afternoon hours in conjunction with the diurnal heating taking place over the island chain, cumulus clouds develop parallel to the island chain or directly overhead maturing into cumulus congestus (towering cumulus clouds) and even sometimes into cumulonimbus clouds. As a result this microclimate phenomenon has an affect on daily rainfall, on Keys classic waterspout formations and lightning that forms from mature cumulonimbus. Please see links on Florida Keys cloud lines.http://www.srh.noaa.gov/key/?n=cloud_lines

Image Courtesy NWS Key West 

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