NOAA EXPERIMENTS IMPROVE FORECASTS DURING WINTER STORMS
ALONG WEST COAST
February 15, 2001 NOAA's National Weather Service meteorologists along the U.S. West Coast and at the Hydrometeorological Prediction Center in Camp Springs, Md., issued numerous winter weather forecasts this week that warned of areas likely to experience high winds, heavy rains, extreme surf conditions and low-elevation snowfall. Those forecasts proved to be right on target and helped many people get ready hours before the storms created havoc from central California to the state's southern border. (Click photo of NOAA's WP-3D "hurricane hunter" aircraft for larger view.)
For several days before that, teams of NOAA-funded research scientists carefully studied numerical weather models, NOAA satellite imagery, and watched the storm begin to march from Alaska toward southern California. These scientists were planning for the right moment before they made their "Go - No Go" decision to fly head-on into those storms while the systems were still offshore.
Operating out of Monterey, Calif., since January 20, NOAA's Pacific Landfalling Jets Experiment's team of scientists has conducted 10 missions to date using one of the NOAA "Hurricane Hunter" P-3 aircraft crewed by NOAA Corps officers and civilians from NOAA's Aircraft Operations Center in Tampa, Fla. The initial results of these experiments have been to provide enhanced weather information to NWS forecasters and computer modelers about the intensity and structure of storms before they strike the U.S. West coast.
The project, nicknamed PACJET, is a collaborative effort between NOAA, the U.S. Navy, other government and university entities. Its goal is to gain further insight into how the "low level jet," a fast-moving current of air centered at 3,000 feet altitude, impacts weather patterns. The experiment concludes Mar. 4.
"Mother Nature provided us with all the elements we were hoping this past week. We're having a very valuable field experience," said Dr. Marty Ralph, PACJET's principal scientist. Ralph is a research meteorologist at NOAA's Environmental Technology Laboratory in Boulder, Colorado.
"Today's weather forecasters rely on numerical models, satellites, weather radar, river gauges and their unique knowledge of the topography of an area as they decide whether to issue severe weather watches or warnings," said Ralph. "Having the ability to use up-to-the minute weather data has contributed to giving the forecasters the confidence they wanted these past few weeks to issue the most timely and more detailed forecast products."
During flights that usually last nearly nine hours, teams of dedicated scientists in the air and on the ground at the experiment's Operations Center in Monterey, monitored data being collected from airborne radars, wind sensors, torpedo-like dropsondes and wind profilers along the coast. These sensors worked together to help the scientists map the atmosphere and the approaching storms. These special observations were fed directly to NOAA's National Centers for Environmental Prediction where high resolution computer models are run daily to provide forecasters critical information on the evolution of these Pacific storms.
Click image for larger view.
This is an example of the tail Doppler radar images from NOAA's P-3 "Hurricane Hunter" aircraft. This shows the "bright band", the redish line across the images from right to left, which is where the frozen precipitation melts, clumping into large aggregates and then becoming rain. It also reflects a higher level of the radar energy during that transition. The location, heading, altitude, etc., of the aircraft are in the image. The images are vertical scans of the systems on both sides of the aircraft by the Doppler radar which is mounted in the tail of the P-3.
Dr. Dave Reynolds, of NOAA's Hydrometeorological Prediction Center, says, "When the models are better initialized with pinpoint information on the location and intensity of existing storms, their predictions of the storm's future course and intensity are improved."
Dan Kozlowski, a forecaster at NOAA's California-Nevada River Forecast Center in Sacramento, Calif., said, "In one instance, our meteorologists were able to develop a more accurate precipitation forecast in terms of timing and intensity, as a cold front swept through the state on January 25."
According to Warren Blier, science and operations officer at the NWS Forecast Office in Monterey, "One of the objectives of the Feb. 12 mission was to collect meteorological data over the Pacific Ocean that would aid in more accurately forecasting the powerful storm that struck southern California later that night. The aircraft flight track was designed to cut through the heart of the developing storm. As these same numerical forecasts are used throughout the country, the potential forecast benefit of such specially-collected data applied to a much larger area than that of the initial region of storm landfall in southern California itself." (For larger view click on NOAA satellite image of storm system that passed over California on Feb. 13, 2001.)
Ralph also remembers the Feb. 12 mission. "There was an explosively developing cyclone off of the southern California coast. The storm was poised to impact the densely populated Los Angeles metropolitan area. The P-3 deployed 16 dropsondes in and around the suspected cyclone center. This event was later associated with as much as eight inches of rain in the San Gabriel foothills and up to seven feet of snow at higher elevations."
Using a new satellite communications link, the P-3 aircraft is able to communicate with forecasters on the ground on a real-time basis, enabling researchers to send NWS staff radar images, audio transmissions, and other information.
As the storm moved southward, NWS Los Angeles-Oxnard senior forecaster Andrew Rorke was busy preparing his forecast update while watching PACJET data. Rorke noted, "PACJET information was very helpful because it gave real-time observations of the storm in a region where we normally do not get data. We were able to use this information to make adjustments to the model forecast that greatly improved the timing and the location of the strongest weather associated with the storm." (For larger view click on NOAA satellite image of storm system that passed over California on Feb. 13, 2001, which includes PACJET data.)
Ivory Small, science and operations officer at the forecast office in San Diego also endorsed the results of the enhanced computer models that day. He said, "As an example of the ferocity of this storm, 2.17 inches of rain fell in Santa Ana, nearly equaling the normal monthly total of 2.33 inches. The storm total of 3.72 inches of rain is more than 50 percent higher than what is normally expected for the entire month of February. The PACJET data was very timely."
National Weather Service Western Region Director Vickie Nadolski says this experiment has proven to be an invaluable tool to the forecasters. "The PACJET data has greatly enhanced our short-term forecasting. Our meteorologists are better able to understand the influence of the low level jet and its correlation with the ocean. This experiment is a prime example of how various NOAA divisions are collaborating with others to benefit the public, the emergency managers and everyone who rely on weather forecasts every day," said Nadolski.
Relevant Web Sites
PACJET, Pacific Landfalling Jets Experiment
NOAA's Environmental Technology Laboratory
NOAAs Hurricane Hunter Aircraft
Barbara McGehan, (303) 497-6288 or Marilu Trainor (801) 524-5692 ext. 226