An El Nino event in the Pacific Ocean affects the Florida Keys and many other places Globally

How can the El Nino event that begins in the Western Pacific have anything to do with our weather here in the Florida Keys? It does because it’s an interaction between the ocean and the atmosphere that reaches all the way around the world.

In years without El Nino the trade winds in the tropical Pacific blow from east to west. This wind causes the warm surface water in the Western Pacific to pile up. As a result the sea surface in Indonesia is three feet higher than at Ecuador.

Off South America cold water upwellings come up from deep cold water off the coast. This cold water is nutrient rich. It supports high levels of plankton, a diverse marine ecosystem and a major fishing industry.

El Nino temps

The rainfall in normal years is found with the warm waters in the Western Pacific where the sea surface temperatures are eight degrees C higher than the Eastern Pacific.

The graph at the right shows the sea surface temperatures in the Pacific Ocean at the equator. The right side is the Western Pacific and the left side is the Eastern Pacific.

An El Nino happens when the pressure increases causing the trade winds to die in the Central and Western Pacific. This causes the thermocline to sink in the Eastern Pacific at the same time climb toward the surface in the Western Pacific. This causes the cold waters in the deep to stay down deep. The nutrient rich cold water is cut off from the mid and upper levels of the ocean. This causes the sea surface temperatures to rise in the Eastern Pacific. In the Western Pacific the winds are blowing toward the east, this pushes the warmer water toward the west coast of South America.

This slowing of the winds, displacement of warm water and increase of atmospheric heat changes the whole global atmospheric circulation. This in turn causes changes in weather patterns far away from the Pacific Ocean where the El Nino is happening. Here's a link to see if there's one out there today.

This warm water creates rainfall for places like Peru, Ecuador and California. These rainstorms are torrential causing floods and mudslides. In Indonesia Australia and Southeastern Africa it causes severe drought and deadly forest and brush fires. It gives the northeastern seaboard of the US a milder than normal winter. In the Florida Keys El Nino results in a less active hurricane season. It allows the west winds aloft to stay strong. These strong winds blow the tops off thunderstorms that would otherwise form into a tropical system. When the phenomenon is large enough, it also causes the hurricane season to end early.

El Nino 1997


This year we are under the influence of an El Nino. Here in the Florida Keys our summer wasn’t all that great. We had lots more days that were rainy and windy. The water wasn’t as clear as is should be. We had only one tropical system to come through the Florida Keys this season. It was Ernesto at the beginning of the hurricane season. It went across the Upper Keys into Florida Bay and on up into the Florida mainland. The season has ended early. We all needed a break from the last two busy hurricane seasons. We need to heal.

Today scientists are better able to predict this weather phenomenon. A network of data collecting buoys have been placed across the tropical Pacific Ocean. Data is collected daily on water temperature, currents and winds in the equatorial band. Ocean-atmosphere models of weather patterns have been drawn up. This enables scientists to warn months in advance of the coming El Nino event.

No El Nino


This weather phenomenon recently occurred in 1986-87, again in 1991-92-93 and 94. The 1997-98 event was very strong. It’s unusual to have this happen in rapid succession as it did in 1991-1994.

This weather event was first observed by the fishermen off the coast of Peru. The unusual warmer waters of the Eastern Pacific would arrive around Christmas time in the event years. El Nino means the Little Boy or Christ Child in Spanish, so this name was used to describe this weather phenomenon that’s able to alter our weather here in the Florida Keys.



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