El Niño is characterized by unusually warm temperatures that move eastward toward Peru’s coast La Niña is characterized by unusually cool temperatures in that same area of the Pacific. The term “El Niño” is so commonly known that it was combined with the scientific term “Southern Oscillation” to form the acronym, ENSO, “El Niño-Southern Oscillation” Why is it called “El Niño”?.

Oscillation is the action of something that shifts back-and-forth An oscillating fan cooled the room as it moved to the right and then to the left. The Southern Oscillation is an alternating pattern of warmer- or cooler-than-normal ocean surface temperatures. Each cycle of the pattern can take years. 2

 Anomalies are deviations from normal, or “nominal”, temperatures  Unusually warm temperatures are shown in red, unusually cold anomalies in blue. Here are the actual temperatures in the top slide, then the anomalous temperatures in the bottom slide.  alysis_monitoring/enso_update/sstanim.sht ml alysis_monitoring/enso_update/sstanim.sht ml 3

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 Each cycle can be strong or weak. The unusually warmer or cooler temperatures can be a few degrees or several degrees away from what has historically been recorded.  Strong ENSO seasons can result in severe weather disruptions in many areas far from the equatorial (tropical) Pacific On the next slide, record 3 events caused by an El Niño event. 8

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 ENSO is not the normal situation.  ENSO cycles are deviations from data recorded over many years  ENSO seems to follow a pattern of every 2-7 years…but lately has been 3-4 years.  ENSO can last months, or LONGER!  Unpredictability is a hallmark of this phenomenon 10

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 Carla-1961  Ike  Katrina-2005  Rita  Tropical Storm Allison-2001  Alicia-1983  And …the Great Storm of 1900!  All are tropical cyclones that have affected our region. 12

 It is an area of disturbed weather (storms) that has a closed circulation in tropical regions and it is not connected to a low pressure frontal boundary. Closed Circulation means the winds blow around it in a circular pattern It has its origins in the tropics It has low pressure in its center, meaning air is rising It is isolated, i.e., not part of a cold front 13

 Warms the air in the tropics  This warm, humid air rises  Convergence of wind currents in the ITCZ are believed to start the rising air to spin, causing a cyclonic action  (See where the winds converge, then diverge…this starts the rising air to spin.) 14

 Is carried “aloft”, meaning high into the atmosphere  The core of a tropical cyclone is warmer than the air surrounding it- that is what makes it “tropical”  It is one method for excess heat to be spread to higher latitudes from the tropics The enormous amount of water in a tropical cyclone carries heat with it as the storm moves away from the Inter Tropical Convergence Zone (ITCZ) 15

16 o …are used to detect tropical cyclones far out at sea o They also track developments as the storms move o Such devices as o Buoys, o Ships, o Weather Balloons, o Satellites, o and Aircraft o all play an important role in measuring the intensities of storms.

Total estimated property damage, 2005 USD  1 MIAMI 1926 $157 billion1926  2 GALVESTON 1900 $99.4 billion1900  3 KATRINA 2005 $81.0 billion2005  4 GALVESTON 1915 $68.0 billion1915  5 ANDREW 1992 $55.8 billion1992  6 NEW ENGLAND1938 $39.2 billion1938  7 CUBA-FLORIDA 1944 $38.7 billion1944  8 OKEECHOBEE 1928 $33.6 billion1928  9 DONNA 1960 $26.8 billion1960  10 CAMILLE 1969 $21.2 billion