Developing El Niño showing similarities to strong 1997/1998 even - Tucson News Now

Developing El Niño showing similarities to strong 1997/1998 event

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An El Niño is developing in the equatorial Pacific Ocean. This means a pool of warmer than average water temperatures is now appearing at the surface of the ocean. Many data sources indicate this could be a strong El Niño event. 

NASA Earth Observatory says "Conditions in May 2014 bear some similarities to those of May 1997, a year that brought one of the most potent El Niño events of the 20th century."

According to NASA Earth Observatory the below images "show the ten-day average of sea surface height centered on May 2, 1997 (left), and May 3, 2014. Shades of red and orange indicate where the water is warmer and above normal sea level. Shades of blue-green show where sea level and temperatures are lower than average. Normal sea-level conditions appear in white."

Sea surface height varies with water temperature due to thermal expansion. As oceans warm, the water expands, which increases the height. This change can be measured from satellites equipped with special instrumentation. As the water cools during a La Niña, the heights decrease.  

See an example of La Niña here and El Niño here.

The swath of red along the equator in the image below shows increased heights. Comparing the two maps you can see the similarities of the developing El Niño events. The 1997 El Niño turned into one of the strongest on record. The Climate Prediction Center (CPC), which tracks El Niño development, warns this year's event may not become as strong as the 1997 El Niño, however it is certainly possible based on current data.  

Plus, while not a complete match, keep in mind the maps were created with two different data sets. Data for the 1997 map was collected by the TOPEX/Poseidon satellite. The data in the 2014 map was gathered by the Ocean Surface Topography Mission/Jason 2 satellite. 


Weather across the world is impacted by El Niño, sometimes with dramatics results. The image below shows how El Niño can impact summer and winter weather across the globe. According to NASA Earth Observatory during the 1997/1998 El Niño the United States "had one of its warmest and wettest winters on record, particularly in California and Florida. Peru, Mexico, and the rest of Central and South America endured devastating rainstorms and flooding. Indonesia and parts of Asia saw disastrous droughts." 

The effects of El Niño on the North American monsoon are not well pronounced. However, winters are generally wetter than average in Arizona. 

The prospect of a wet winter isn't a bad thing for the western U.S. The image below shows the latest U.S. Drought Monitor update for the continental U.S. (CONUS). Drought covers about 40% of the lower 48 states. Most of the drought conditions stretch west of the Mississippi River through Texas into Arizona and California. Over 98% of Arizona is experiencing drought conditions. 

For Tucson, the 1997 monsoon was a dry. The city had very little rain in June and July with near-average totals for August and September. (See table below for the numbers from the Tucson National Weather Service.) August and September are also generally the months of greatest tropical activity. 

  June (15-30) July August September Total
Average 0.15" 2.25" 2.39" 1.29" 6.08"
1997 0" 0.51" 2.32" 1.43" 4.26"

However the rain total from the cool season, November 1997 to April 1998, was above average with 8.77". All but about 2.5" of that rain fell in the winter months of December, January, and February. According to Glenn Lader from the Tucson National Weather Service, 82% of the cool season rain during an El Niño event produced above average numbers.  

For the complete Tucson National Weather Service report on how El Niño and La Niña influences weather in Arizona click here.




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