Drought?

The latest Southwest Climate Outlook from the CLIMAS project has some interesting tidbits:

• 2005 was the worst fire year in recorded history in Arizona
• despite the wet early part of the year, significant parts of the southwest are still in drought
• the monsoon has favored Arizona, but been weak across New Mexico
• there's more water in the reservoirs than last year at this time, but they're still well behind "normal" for this time of year
• El Niño isn't offering any promise of relief in the coming winter

(click through for my attempt to 'splain some more about the El Niño stuff)

The El Niño thing is tricky to explain. We're in "ENSO-neutral" conditions, meaning temperatures in the equatorial Pacific are right in the middle, neither cold nor warm. Given the correlation between those temperatures and our winter rainfall, that might cause one to think that means we can expect "average" rainfall/snowfall this winter. That would be wrong. Instead, all the forecasters can say is there is nothing in the current situation to favor either a wet or a dry forecast. We still could have either, but there's nothing to push the odds in one direction or the other.

Think of it with a gambling metaphor. You roll a dice. 1 or 2 is a dry winter, 3 or 4 is in the middle, and 5 or 6 is wet. In an El Niño winter, the dice are loaded, and you're more likely to get a 5 or a 6. A 1,2,3 or 4 is possible, just less likely. In a La Niña year (cool Pacific temperatures), you're more likely to get a 1 or 2. Again, 3,4,5 or 6 are possible, just less likely. This year, the odds are even across the board. Does that make sense?

Posted by John Fleck at August 25, 2005 08:40 AM