In fact, Hurricane Zeta would not have gained so much strength and fooled forecasters if it were not for the same the weather system whose howling winds fanned the flames of the California blazes and fed frigid air into the Oklahoma ice storm.
Zeta was never predicted to become as strong as it did. Forecasters at the National Hurricane Center forecast that it would make landfall in southern Louisiana on Wednesday as a Category 1, its intensity held in check by cooler ocean waters near the coast and hostile high-altitude winds.
But as the satellite image above and the loop tweeted by Weather Channel meteorologist Stu Ostro (below) show, the hurricane unexpectedly took advantage of a handoff in energy from the rambunctious weather system to its northwest. Instead of a Category 1 at landfall, Zeta crashed ashore as a near-Category 3 storm, the strongest on record so late in the season in the Lower 48.
The hurricane managed to capitalize on upper-level winds streaming through Texas and Oklahoma generated by an unusually sharp dip in the jet stream for late October. This dip allowed record cold to crash through the northern Rockies and into the Plains, with temperatures up to 60 degrees colder than average and as low as minus-33 degrees.
The upper level winds roaring from south to north along the eastern flank of the jet stream dip facilitated diverging air flow above and out ahead of the hurricane. This encouraged air to rise, cool and condense into clouds and precipitation, and led to an increase in thunderstorm intensity within Hurricane Zeta, which overwhelmed anything that might inhibit it.
Astonishing forecasters, the storm’s winds increased by 45 mph in the last 26 hours before landfall.
For a more technical take on what happened, here’s the Hurricane Center’s explanation written in a forecast discussion Wednesday afternoon. There’s a clear sense of exasperation at seeing this storm defy expectations that cuts through the scientific jargon.
“Somewhat surprisingly, Zeta has rapidly intensified this afternoon,” meteorologists wrote. “Although the hurricane has been moving over marginally warm [sea surface temperatures] and relatively low heat content waters, it has intensified from 80 [knots] to 95 [knots] in about 6 hours. It is possible that this intensification can be at least partly attributable to a conducive interaction with an upper-level trough [dip in the jet stream] located a few hundred miles to the west-northwest of Zeta.”
In meteorology, extremes tend to beget extremes, and Zeta’s fury was yet another example. It was a hurricane paradoxically intensified by an ice storm that cut power to hundreds of thousands several hundred miles away.
The ice storm, in turn, followed an extraordinary early season snowstorm across the Upper Midwest to the northern Rockies, with massive Colorado wildfires temporarily brought down out of the crown of trees to the forest floor by below-zero temperatures and more than a foot of the skiers’ gold.
The Arctic air mass that poured into the West with the buckling jet stream helped form a high-pressure area over the Great Basin, which contributed to 96 mph Santa Ana winds in Los Angeles County. These winds spread destructive wildfires that struck Irvine and other parts of Orange County.
The broad satellite view (below) lays bare the outcome of this causal chain — from the plumes of wildfire smoke blowing from land to sea in Southern California, to the ice storm over the Southern Plains and Hurricane Zeta crossing the Louisiana coast in the northern Gulf.
In other words, when it comes to Hurricane Zeta, the ice storm, wildfires and more, everything was interconnected. The symbiotic relationships between weather systems are rarely so apparent simply by looking at a single satellite image, with two storms resembling conjoined twins.
With Hurricane Zeta, the potential for the upper-level jet stream to give the storm a tremendous boost may not have been anticipated, but it wasn’t chaotic.
In fact, it was rather simple and elegant.