Global rainfall pattern could offer weather prediction three weeks out

[Jim__]

From phys.org:

Averages of all January–March MJO events from 1979–2016. Green shading shows below-average OLR (outgoing longwave radiation, or heat energy) values, indicating more clouds and rainfall, and brown shading identifies above-average OLR (drier and clearer skies than normal). The purple contours show the location and strength of the Pacific jet at the 200-hPa level (roughly 38,000 feet at that location). Note the eastward movement of the wet and dry areas. How far the Pacific jet extends past the international dateline also changes with the phase of the MJO. Credit: Carl Schreck

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Earth's atmosphere is chaotic, making it difficult for forecasters to predict weather more than 10-13 days in advance. However, research has increasingly shown that large-scale patterns of variability and relationships between states of the atmosphere in two faraway locations, called "teleconnections," can help extend prediction skill beyond this limit.

"Few researchers have applied this mechanism to weather prediction," said Kai-Chih Tseng, atmospheric science graduate student at Colorado State University (CSU). "Especially from two weeks to three months, which has been known as a 'prediction desert' in the past."

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For decades, scientific evidence has confirmed that the major tropical rainfall pattern called the Madden-Julian Oscillation (MJO) can influence the weather in our neck of the woods. The MJO travels eastward around the equator, repeating its route every 40-50 days. Its global trek is divided into eight phases based on the MJO's location. As it moves, via interactions between the ocean and atmosphere, it sends ripples through the atmosphere that can contribute to extreme events in the U.S., like Arctic air outbreaks, extreme heat events, and flooding.

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