From the High Country News weblog The Range (Ed Quillen):
For the West, this means it will be wet in the north and dry in the south…
Colorado is in the middle between north and south in the West, so fluctuations on the jet stream will determine how much of the state gets buried in December and January…
In some years, there’s talk of “La Nada” — the nothing, or at least nothing out of the ordinary. El Niños and La Niñas tend to run in three- to seven-year cycles, and if you want to sound technical, you can call it ENSO for “El Niño/La Niña Southern Oscillation.”
La Niña was a hot topic last week when members of the CWCB, water providers and others huddled up at Denver Water to answer the question, “Drought in 2011?”. Below are my notes from the meeting:
Water Year 2010 review
Nolan Doesken kicked things off with a look back at the past year.
A year ago October was wet and snowy but in November everything dried out. Northern Colorado was dry until the spring when the precipitation pattern shifted north. Wind speeds were low over the winter leading to a decline in wind energy production in northeastern Colorado. There was a wet spring and early summer in northeastern Colorado. Also in April there was a series on large dust events in the San Juans. The runoff was fast a furious with sudden warming at the end of May. Colorado experienced a strong but confined monsoon mid-July to around August 15.
He said that yesterday’s precipitation was the, “first widespread event in 2 months.”
Overall, “Most of the state ended up near average for precipitation,” he said, and added that, “This is the first time in history that we have had 3 near average years in a row.”
According to Doesken, the summer was the 15th warmest on record, statewide.
Short-term forecast
Triste Huse from the National Weather Service presented the short-term weather outlook. She said we can expect a good storm around Tuesday of next week. She showed a slide of comparing the historical precipitation for the 45 day period between August 1 and October 7. 2010 was the third lowest on record. Her 60 day comparison, ending October 7, had 2010 in first place for dryness. She added that September 2010 was the 7th warmest on record.
Long-term forecast
Klaus Wolter started off his presentation by saying that, “La Nina is on a steam roller.” The Multivariate ENSO Index is at it’s lowest level in 94 years, he said, adding that, “This is quite remarkable,” and, “The system can’t really get any colder.” (ENSO = El Nino Southern Oscillation). He told the group, “If you’re making a bet on the first snowfall,” bet on next Tuesday. His research shows that, “We’ve never really had a dry winter with La Nina.”
He told the water providers that if this La Nina turns out to be a two year event, “You better hope that the first year is not too bad because the second year will get you.” He said, “The odds are better than 50-50 that this will be a large La Nina with a normal, at best October.” He believes that we’ll have a few months above average moisture for winter, “but the runoff season next year will be on the dry side.”
“We are not on a 2002 path at this point,” he said, predicting a near normal winter and a dry spring. If La Nina continues it could be the start of a dry 2012.
Water provider updates
Bob Steger from Denver Water asked each of the water providers present to update the group on current operations and any plans for dealing with the possibility of the D1 drought continuing or worsening. Most providers are in good shape regarding storage. Aurora and Colorado Springs are planning work on Homestake Reservoir in 2012 so they will be drawing it down it prior to the work starting. Denver Water does not plan any extra releases for the next few months – they’re just going to match demand.