Hot Items 2004U.S., Mexico join forces to improve monsoon forecasts
Through September, NOAA scientists are focusing their attention on storms in Mexico and in the deserts of the American southwest for clues that may ultimately lead to better predictions of summer rainfall in the United States.
For nearly four months, scientists from more than 30 universities, laboratories and agencies in the United States, Mexico and Central America have joined forces for the North American Monoon Experiment, or NAME, the largest study ever of the midsummer rains that affect farming, ranching, wildfire control, weather resource management abnd public safety throughout the southwestern U.S. and northern and western Mexico.
The researchers are collecting extensive atmospheric, oceanic and land-surface observations with a wide range of instruments in the core region of North American monsoons -- northwest Mexico, the southwest U.S. and adjacent oceanic areas. The data will be used to improve global weather and climate models by better representing rainfall processes.
U.S. participants also include more than 25 scientists from NOAA's National Weather Service, the National Science Foundation, NASA, Vaisala and the U.S. Department of Agriculture and Defense. NAME forecast operations, located in the National Weather Service Forecast Office in Tucson, Ariz., and in Mexico City, are coordinated with Mexico's Servicio Meteorologico Nacional and the NWS's National Centers for Environmental Prediction.
"This field campaign will improve our understanding of the daily cycle of precipitation in the complex terrain of the core monsoon region," said Wayne Higgins, NAME lead scientist and the principal climate scientist at the NOAA Climate Prediction Center. This new knowledge may also contribute to more accurate predictions of the droughts and floods associated with monsoons for Mexico and the western U.S., he said.
Summer monsoons are seasonal reversals of wind direction that occur in response to temperature differences between the land and sea, accompanied by increases and decreases in precipitation, and can occur over all low-latitude continental regions.
The North American monsoon, though much weaker than the Asian monsoon, exerts a strong influence on the precipitation, temperature and wind patterns in the core monsoon region but also over much of the western half of North America and adjacent ocean areas.
NAME's area of focus stretches east from the Gulf of California, across the Sierra Madre Mountain range in northwestern Mexico and into the desert southwest of the U.S. These locations get most of their annual rainfall during the summer monsoon months, but forecast models have trouble predicting the fast and intense precipitation that can leave the public exposed to flash flooding and severe thunderstorms.
"NAME will increase the National Weather Service's ability to forecast monsoon-related weather at time scales ranging from just a few hours to a few months," said Erik Pytlak, science and operations office for the Tucson forecast office, who has served as co-coordinator for NAME forecasting operations. "Our customers and partners call upon the National Weather Service, including our office here in Tucson, to provide this information so that they can make decisions -- from postponing sporting events to preparing our partners for possible response and recovery actions, putting up flood barricades, allocating and distributing wildfire management resources and providing water resource planners key information to aid in their ongoing drought management efforts."
Forecast responsibilities with NAME have been extensive. Daily forecasts focus on synoptic and large mesoscale features and associated weather phenomena throughout the southwest corner of the United States and most of Mexico. Weather briefings are then held at the University of Arizona's atmospheric science department.
"This has been a learning experience for all of us," Pytlak said. "Forecasting for a large area with specific science needs has been very different from our typical responsibilities."
Scientists and forecasters are excited about the data collected so far. "The results we've gathered have been very good, very intriguing," Pytlak said.
"The 2004 monsoon season has been unusual," Pytlak said. "It has allowed us to catch interesting features set off by unusually strong Gulf of California surges and back door cold fronts into New Mexico. This has had ramifications for storm prediction not only in the monsoon region but east of the Continental Divide. In addition, we sampled a break in the monsoon, which will allow the scientists to study what happens when the monsoon circulation gets disrupted," Pytlak said.
In the last few weeks of data gathering in September, forecasters hope the monsoon will become more typical.
The 2004 field campaign represents the middle of NAMES's eight-year life cycle, which includes the planning, preparation, data collection, field analysis and modeling phases.
NOAA and university scientists spent May and June establishing observing networks and making them operational. One team led by Michael Douglas, a NAME principal investigator from NOAA's National Severe Storms Laboratory in Norman, Okla., distributed about 300 rain gauges and set up pilot balloon observing sites at strategic locations throughout Mexico. Douglas is fluent in Spanish and has spent years obtaining and installing affordable weather observing equipment for Central and South America. He then trains local people to operate the systems.
"One of our pilot balloon observing sites employs a member of the city police force," Douglas said. "The observer comes to make the morning observation in uniform, complete with pistol."
Several Mexican C-band radars are part of the observing network along with the Boulder-based National Center for Atmosperhic Research's S-Pol polarized Doppler radar, NOAA's radars on the P-3 research aircraft, and WSR-88D radars from the southern part of the U.S. Polarized radars give superior estimates of rain rates and can distinguish between rain, snow and hail. The rest of the observing network includes hundreds of simple rain gauges, three integrated sounding systems, hundreds of special radiosonde launches from both U.S. and Mexican radiosonde stations and wind soundings from two dozen pilot balloon sounding sites.
During NAME's six-week intensive opreational period from early July to mid-August, Douglas coordinated the aircraft and oceanographic data gathering activities of NOAA's P-3 research aircraft, research ships from the Mexican navy and a Mexican research institution, all based in Mazatlan, Mexico.
In a few years, once scientists have analyzed the massive amounts of data gathered during NAME, they expect the results will improve NOAA's ability to monitor and predict drought and heavy rainfall, especially in the desert southwest. Ultimately this information will help communities better prepare for the acute weather conditions associated with monsoons.
8/30/2004