Precipitation expected due to monsoon, El Niño in Colorado, Wyoming, Kansas and Nebraska
June 30, 2017
It's very possible much of Colorado's summer moisture could come from the upcoming North American Monsoon.
According to the latest Climate Prediction Center's official three-month precipitation outlook for July, August and September, there are equal chances of either normal precipitation or above or below normal precipitation for Colorado, also most of Wyoming, nearly all of Nebraska and the entire state of Kansas. Precipitation chances are slightly higher for northeast Wyoming and extreme northern Nebraska (as of the June 15 CPC outlook.)
Interestingly, eastern Colorado, since 1895, has received an impressive 35 to 40 percent of its annual precipitation during the monsoon season in July, August and September.
"Then, in the last 15 years, eastern Colorado's impact from the monsoon has increased to 40 to 45 percent of its yearly precipitation," said Meteorologist Matthew Rosencrans at the CPC in College Park, Md. Rosencrans noted other states also benefit from monsoonal rainfall include western Nebraska and western Kansas.
The Monsoon, which is the seasonal wind reversal, brings hope for moisture from thunderstorms during the first two-thirds of the summer.
"As we move into the seasonal period where the Rockies experience the secondary wet season called the North American Monsoon from early July through late August, the long-term guidance is indicating no bias toward above- or below-normal precipitation during this time. Specifically for northeast and east Colorado, indications point to equal chances (average) of precipitation coming in above or below seasonal normal through early September," said Meteorologist Kyle Fredin at the National Weather Service in Boulder, Colo., which covers northeast Colorado, which is from the Continental Divide to the Palmer Divide to the Nebraska border.
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For western Colorado, and even extending to the Front Range, the monsoon is a seasonal pattern that pumps moisture from the Gulf of California northeastward to the Four Corners, the quadripoint in the southwest U.S. where the four corners of Colorado, Utah, New Mexico and Arizona meet. This moisture can be observed by an increase in dew points.
"The normally very dry desert southwest suddenly has dew points in the 50 to 60 degree range (not as impressive for the Midwest or east coast, but quite humid for those of us more used to the dry climate). The result is that afternoon thunderstorms become much more likely," said Becky Bolinger, Ph.D., climatologist/drought specialist at the Colorado Climate Center, Colorado State University; Department of Atmospheric Science in Fort Collins. "Even along the Front Range, locations like Denver and Colorado Springs see a healthy bump in average precipitation in the late summer. This can sometimes be observed in the eastern plains (more likely in southeast Colorado rather than northeast Colorado), but that can be more dependent on the strength of the Monsoon in each given year," Bolinger said.
RELIEF FOR WYOMING
Meanwhile, parched northeast Wyoming could receive some moisture relief this summer.
"The northeast part of Wyoming has slightly better chances of receiving above-normal precipitation, which would be of help for conditions there. But, at the same time you have elevated chances of higher-than-normal temperatures. With some of the wind they have gotten up there (in mid-June) drying things out, the precipitation part may just make it end up 'not as bad as it could be,'" said Tony Bergantino, deputy director of the Water Resources Data System — Wyoming State Climate Office and Wyoming CoCoRaHS State Coordinator.
"For the remainder of the state, however, the signal doesn't push the odds one way or the other, toward above-normal, below-normal, or normal precipitation," Bergantino said.
Regarding the central Plains of Kansas and Nebraska …
"ENSO (El Niño Southern Oscillation) neutral conditions are now expected to persist through the fall of 2017 with better-than-even-chances for weak El Niño conditions to develop toward winter. This potential El Niño is not expected to have a significant impact for the central region of the U.S. this year," said Chad Omitt, warning coordination meteorologist for NWS in Topeka, Kan.
"In short," Omitt said, "We expect better-than-even chances for warmer-than-average conditions through the summer with equal chances for precipitation across the region. That is to say, there is no meaningful signal that favors wetter or drier conditions in the next few months across the region as we head through the summer season."
Regarding the big climatic picture, "Most of the models are showing very little chances for either an El Niño (warmer sea surface temperatures) or a La Niña (cooler sea surface temperatures) to form. It is most likely that we will stay in ENSO neutral conditions throughout the rest of the summer, with a slightly increased chance we'll go to an El Niño in the fall or winter. This means the ocean is not going to be a good predictor for what's to come, which makes a seasonal forecast even harder than it already is," Bolinger said.
Another climate specialist sees potential for a weak El Niño to develop late fall through winter 2017-18.
"The three-month period (March-April-May) ONI (Oceanic Niño Index) is indicating sea surface temperature anomalies of +0.4C across the eastern equatorial Pacific Ocean. El Niño conditions are defined as seeing five consecutive three-month periods of sea surface temperature anomalies of +0.5C or greater," said Mark Wankowski, climate specialist for NWS in Pueblo, Col.
He noted, however, "some of latest model guidance is suggesting ENSO Neutral conditions will persist throughout the summer and fall."
Meteorologist H. Michael Mogil, CBM, CCM, with "How the Weatherworks" based in Naples, Fla., also expected ENSO to remain neutral.
"Looking at animated maps of observed sea surface temperatures, I saw a slight cooling trend in the eastern tropical Pacific, which could mean we're in a weak neutral oscillating pattern," Mogil said. "I don't see any extremes showing up in the CPC summer outlook. However, I would certainly look for dry weather across the Plains as the usual summer upper level high pressure system sets in." Mogil and a colleague recently launched a global climate website offering educational weather and preparedness information at http://www.globalweatherclimatecenter.com.
Regarding summer temperatures, this latest CPC outlook is forecasting slightly higher than normal temperatures for much of the Rockies and Plains states, including Kansas, Nebraska, most of Colorado and most of Wyoming. One particular exception is southwest and western Colorado which show slightly higher-than-normal summer temperatures. Meanwhile, for the rest of Wyoming, equal chances for average, above- or below-average temperatures are forecast from north/central Wyoming to extreme northwest Wyoming.
Bolinger said eastern Colorado and the Front Range could see a high frequency of 90 degree temperatures, and probably several 100-plus degree temperatures as well.
"These hot temperatures (combined with possible drier conditions in July) would result in an increase in evaporative demand. In non-irrigated areas, this will result in some vegetative stress and the soils are likely to become dry. Quick afternoon thunderstorm events may help alleviate the dryness a little bit," Bolinger said.
"With above-average heat noted in the longer term models, farmers and ranchers will need to monitor soil conditions during any longer term hot periods," Fredin said.
In the very northwestern part of Wyoming, the signal isn't strong enough to push the forecast one way or the other so the area has equal chances for above-normal, below-normal, or normal temperatures. The northeastern counties of Crook and Weston, and northeastern part of Niobrara County are still in abnormally dry (D0) conditions," Bergantino said.
However, what could possibly bring a wetter-than-normal impact is the possibility of a tropical system.
"Tropical systems remain the wild card going forward. The Atlantic tropical region has above-normal sea surface temperatures from Africa to the Caribbean, with ENSO neutral conditions in the Pacific. A slightly higher tropical season in the Atlantic is expected, but the number of systems that may enter the Gulf of Mexico is unknown. If the eastern Gulf (of Mexico) sees an uptick of tropical weather, than it is likely some of it will feed north into the corn belt, increasing wetness," said Allen Dutcher, associate state climatologist with the Nebraska State Climate Office in Lincoln, adding, "This might be beneficial if drought conditions expand, but if wetness remains an issue, than these tropical systems would add to the misery of too much moisture."
One aspect that meteorologists and climatologists agree on is that there can be different analyses for seasonal forecasts in states.
"Late summer can be a particularly difficult time to forecast, especially a long-term forecast. That's because a lot of the precipitation that can fall during the season is the result of localized heating and moisture. This is different than winter, when precipitation patterns are more large scale and — more follow along more predictably — with troughs and fronts that we can see progressing across the country and can better anticipate when those storms will arrive," Bolinger said. "In summer, you're probably aware that storm clouds can seemingly bubble up out of nowhere, and rain can arrive very suddenly and leave quickly. It's hard enough to predict these individual storms within a week, it's even that much harder a month or more out."
As Bolinger put it, "We can keep our fingers crossed that the monsoon proves to come on strong and provide some relief to the hot temperatures that are expected."
For more information: http://www.cpc.noaa.gov or http://www.cpc.noaa.gov/products/predictions/long_range/seasonal.php?lead=1
— Hadachek is a freelance writer who lives on a farm with her husband in north central Kansas and is also a meteorologist and storm chaser. She can be reached at: email@example.com