While La Niña is considered a good thing for skiers and snowboarders in the Pacific Northwest, it means Texans could see a mild and dry winter.
The Sept. 14, 2017 advisory from the Climate Prediction Center states “There is an increasing chance (~55-60%) of La Niña during the Northern Hemisphere fall and winter 2017-18.” Previous advisories indicated computer models were leaning toward a neutral winter, but have been recently trending toward a La Niña winter. Based on this forecast, the CPC has issued a “La Niña Watch.”
The CPC says a La Niña Watch or an El Niño Watch is “Issued when conditions are favorable for the development of El Niño or La Niña conditions within the next six months.” The advisory states the El Niño/Southern Oscillation (ENSO) is neutral at the moment, with sea surface temperature (SST) index values between -0.1°C and -0.6°C.
For La Niña conditions to exist, there must be one month or more of a negative sea surface temperature anomaly of -0.5°C or less in an observed region of the equatorial Pacific Ocean. Conversely, seeing one month or more of a positive sea surface temperature anomaly of 0.5°C of greater – seen over that same region – means El Niño conditions are present.
Texas is usually dry during La Niña winters and wet during El Niño winters. Last year was a mild La Niña, and the Austin area is above the yearly average to this point. NWS Data from Camp Mabry on Sept. 15 shows Austin in 2017 has received 2.75” rain more than the normal, which is defined as the average 1981-2010. Austin-Bergstrom International Airport is more than 7 inches above normal for 2017. Mabry has not received any rain in the month of September while ABIA has only seen a trace of rain, according to the NWS.
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