Weather
NOAA: La Nina Moves In For The Winter
by NOAA
November 9th, 2017
A La Nina climate pattern has arrived and is likely to persist through the winter, according to an advisory issued by NOAA’s Climate Prediction Center today. Scientists say there is a greater than 50-percent chance La Nina will also be in place February through April 2018.
This is the second winter in a row with a La Nina, and like last year, forecasters expect this one to be weak. Last year, this weather phenomenon extended from July 2016 to January 2017 before a return to neutral El Nino Southern Oscillation (ENSO) conditions.
La Nina: What it is, and what can we expect
La Nina (translated from Spanish as “little girl”) is a natural ocean-atmospheric phenomenon marked by cooler-than-average sea surface temperatures in the central Pacific Ocean near the equator, the opposite of El Nino (“little boy”).
Typical La Nina patterns during winter include above-average precipitation and colder-than-average temperatures along the northern tier of the U.S. and below-normal precipitation and drier conditions across the South. NOAA’s 2017 Winter Outlook anticipated that a weak La Nina was likely to develop. Therefore, significant changes are not expected when the Winter Outlook is updated on November 16.
It is now Feb 28th, 2018, and I am assuming that La Nina typical, water temperatures, still exist in the tropical Pacific. With that said, according to my observations, beginning in late Jan, upper level wind patterns, across the Pacific and North America, seem to be blowing in a manner similar to what is usually observed during El Nino events.
Across much the SE. USA,the surface weather pattern, again, beginning in late Jan. 2018, made a quite abrupt transition, from the cool-cold, and mostly dry pattern, typical of La-Nina events, to a much warmer, and much wetter pattern.
Does anyone reading this comment, have any idea as to why the subtropical southern branch, of the jet stream, which was practically non existent, during the period of Nov 2017 to Late Jan. 2018, has become so energetic as of the last four weeks or so ? Is the reemergence of the Southern jet stream, the result of a decaying La Nina, a foreseen result of a mature La Nina, in some way associated with La Nina, an independent variable, not, associated with the current La Nina, or the result of, or expression of, the present La Nina, occurring in conjunction with, one, or more, other global climatic cycles ?