It’s official! NOAA declared us officially in a La Nina phase. We’ve been watching for the last few months a growing anomaly of cooler waters developing off the coasts of Peru and Ecuador. La Nina is the opposite of El Nino, where eastern Pacific waters are warmer than normal.
This occurs when the trade winds (winds that push east to west along the equator) increase, thus pushing surface ocean water warmed by the strong sun westward where it pools to above normal temperatures near Australia and Papua New Guinea. The result creates upwelling along the South America's coast, which means the deep, cold ocean waters are pushed up to the surface.
La Nina's effect on Minnesota weather is a bit murky.
Whereas El Nino is a very strong correlation for milder winters – 3 out of 4 El Nino episodes result in warmer than normal Minnesota temperatures – La Nina almost cuts 50-50 with a slight favorability toward the cooler side.
There’s also bit more correlation to wetter winter conditions (either more rain or snow).
One must keep in mind that numerous things impact seasonal weather patterns and La Nina is just one. If other forces are stronger, which our climate models suggest this year, La Nina’s impact may not be much.
Climate change link to wildfires in California
California officially is experiencing the biggest fire in its history. Thousands are being evacuated from Oregon where they too are having a raging fire season along with most western states.
There are currently over 100 fires. While a viral story, the gender reveal party isn’t the cause of all this chaos & smoke, that’s one fire.
Western fire seasons have been getting longer and more severe as temperatures warm. A clear climate change signal is being observed. Nearly double the acreage is being burned now compared to 40 or 50 years ago.
In the West, they rely on winter and spring for rainfall and snowfall in the mountains to replenish aquifers and create greenery. During the hot, dry summer months vegetation dies off or goes dormant and fire season usually starts end of summer or early fall – it’s a normal, annual cycle here.
These fire seasons however are starting earlier and ending later, and they've become more severe with more frequent extreme heat waves like we saw over Labor Day weekend (much of CA was baking with 100+ degree temps).
Winter precipitation is becoming much more variable & less dependable as well, which leads to drier summer conditions.