This year has seen a lot of record setting events from the COVID-19 Pandemic, to the horrific wildfires, to the continuing Tropical Cyclone Season that has seen so many named storms that the Greek Alphabet has to be used. The National Oceanic and Atmospheric Administration (NOAA) has explained that the already prolific “Hurricane Season” could be enhanced by the phenomenon known as La Nina. The NOAA bulletin issued on September 10th suggested that La Nina would weaken the wind shear (Definition shown later) over the Caribbean Sea and the tropical Atlantic Basin which enables storms to develop and intensify. That’s according to Mike Halpert who is the Deputy Director of NOAA’s Climate Prediction Center. The La Nina could last into the winter which could have a serious effect on the kind of winter we here in the Pacific Northwest will be experiencing.
We should go over the terminology involved in order to better understand what this means. El Nino is defined as a warm water current (shown in red/orange) that appears annually, around Christmastime, along the coasts of Ecuador and Peru. The name El Nino means the boy child and refers to the “Christ Child” who’s birthday is celebrated in December when the warm water pool extends itself closer to the South American coast. It was first discovered or noted by the fisherman who found warmer water where they usually would catch fish.
La Nina is defined as a cold water current (shown in blue) that appears annually, around Christmastime along the coasts of Ecuador and Peru. The name La Nina means the girl child and is the opposite of El Nino and is the cool water pool that extends itself closer to the South America in December.
It seems obvious that El Nino and La Nina can’t occupy the same area along the South American coast at the same time. That is where another term comes into play. The ENSO or El Nino-Southern Oscillation. El Nino is often called the warm phase of ENSO while La Nina can be called the cold phase of ENSO. Often the sea surface temperatures waver between the two in the same season.
What would you call it when neither El Nino nor La Nina come to visit the West Coast of South America? I guess you could call it the “nothing” and that is just what they decided to call it. In Spanish it is La Nada.
El Nino’s warm water pool actually deflects the Jet Stream in the Winter in such a way as to set up a high pressure ridge over the Pacific Northwest. That ridge keeps the cold air and the Winter storm track to our North or South and tends keep us warmer and drier. During an El Nino year there is usually less tropical storm activity in the tropical Atlantic due to increased vertical wind shear over the area.
Vertical wind shear is the change of wind direction with height. In order to build the storm clouds it takes to produce a hurricane there must be steadily rising columns of air and the change of wind direction as the air is rising tends to stop the development of the storm clouds.
La Nina’s cold water pool has the opposite effect and deflects the Jet Stream so as to send the Winter storms right at us. I know what you are expecting me to say next. Which one is controlling our weather now and what kind of Winter can we expect? The experts say we are in the La Nina now. It is too early in the season to make a solid prediction for Winter. The best time to do that is mid-November when the sea surface temperatures are set up for the Winter months. That prediction would be for the actual Winter months of December, January, and February.
We could even see a moderate La Nina which might give us some winter storms, but not the strongest heavy snow producing storms. As for how much more severe the Atlantic hurricane season will get that will become obvious very soon. We’ll just have to wait to see what will actually happen.
Let me know what you would like me to talk about or explain. You can comment below or email me at: [email protected]