La Niña's Persistent Presence: A Weather Phenomenon Explained
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Chapter 1: Understanding La Niña
La Niña conditions, which began two years ago, are projected to persist, as indicated by the National Oceanic and Atmospheric Administration (NOAA). Currently, the La Niña phenomenon in the tropical Pacific Ocean is reaching near record levels for this time of year, leading to the likelihood of a third consecutive fall and winter season with this uninvited guest.
La Niña, often referred to as El Viejo or "the old man," and its counterpart El Niño represent alternating phases of a natural weather cycle known as the “El Niño-Southern Oscillation” (ENSO). During the La Niña phase, easterly trade winds strengthen across the Pacific Ocean, resulting in an upwelling of cooler waters from the ocean's depths.
The equatorial trade winds in the Pacific blow from east to west. When these winds weaken, they are less effective at moving surface waters, allowing solar heat to accumulate and warm the ocean's surface (El Niño). Conversely, during the La Niña phase, stronger trade winds displace the warmer surface waters toward the western Pacific.
This process initiates off the western coast of South America, where the displacement of warm surface water allows cooler water from deeper ocean layers to rise and fill the gap. This creates a cold-water wedge that is pushed westward, forming a long plume extending from South America to the western Pacific.
Good News — Bad News
One positive aspect of La Niña is the cooler water in the tropical Pacific, which exerts a cooling effect on the atmosphere and temporarily mitigates global warming. However, it is essential to note that this cooling does not signify a reduction in greenhouse gases. When El Niño conditions return, global warming is expected to intensify.
It's also important to highlight the plight of the long-suffering residents in the American Southwest, who will find little comfort in another year dominated by La Niña. The region has endured a twenty-year megadrought, severely depleting water reserves and creating conditions ripe for devastating wildfires.
La Niña generally shifts wet weather northward, resulting in drier conditions for Southern California and the Southwest while increasing moisture in the Pacific Northwest. The prolonged presence of La Niña exacerbates the ongoing megadrought and stresses the region’s forests.
However, the effects of La Niña extend far beyond the West, reaching into the southeastern United States. Residents along the Atlantic and Gulf Coast can anticipate increased wind, rain, and destruction.
Chapter 2: Implications for Hurricane Activity
The first video titled "La Niña is Coming…" delves into the effects of La Niña on weather patterns, emphasizing its potential to influence hurricane activity.
The cooler waters in the equatorial Pacific have significant repercussions. The cooling of the oceans affects atmospheric temperatures, which in turn influences air circulation patterns. Specifically, La Niña alters the position of the jet stream, pushing it northward. Although the jet stream operates high above us, its effects reach down to the surface, impacting weather across North America. One noteworthy connection is between the cooler Pacific waters and an increase in tropical storms in the Atlantic Ocean, thousands of miles away.
This interaction occurs through a phenomenon known as “wind shear.” Warm, moist air rises from the ocean's surface between North Africa and the Caribbean. As this warm air ascends, it creates a sea breeze that fills the void left behind, further promoting upward movement. The greater the volume of rising air, the stronger the winds become, leading to the formation of a tropical storm.
For a storm to strengthen, its moist, warm air must continue to rise. However, if mid- and upper-level winds differ in speed and direction from the surface winds, this creates wind shear, which can inhibit storm development. Essentially, increased wind shear results in fewer tropical storms, while decreased shear creates conditions favorable for storm formation.
La Niña contributes to this dynamic by shifting the jet stream northward, resulting in calmer conditions aloft over the Atlantic hurricane corridor. Consequently, there is a greater likelihood of tropical storms developing, and more of these storms have the potential to escalate into hurricanes.
The second video titled "La Niña coming with a Big Change..." explores the potential impacts of La Niña on future weather events, including the likelihood of increased hurricane activity.
In summary, it seems that the “Old Man” may continue to exert his influence for another year.