Volume III, Issue 2

The Future of Weather Forecasting Utilizing Global Positioning System
by Gary Chatelain

The NWS has been launching weather balloons twice a day since before WWII, in order to observe changes in air pressure, temperature, humidity and winds in the upper atmosphere. In fact, forecasting the weather would be nearly impossible without such data. Despite exponential technological advances elsewhere in meteorology, this arena has essentially remained unchanged aside from early computer tracking and then software upgrades in the late 80's to 5¼ inch floppies for data processing. The old system utilized basic triangulation of three known points, one of which was the balloon borne radiosonde, transmitting a radio signal back to earth. This allowed for the calculation of the winds along with the other monitored data. As recent March of this year, some of the oldest of this type equipment was still in operation at the NWS in Shreveport. I can recall a tag riveted to the front panel of our old tracking equipment indicating a serial number of 6 which was issued to the then, U.S. Weather Bureau. After talking to Ernie Ethridge, long time meteorologist and friend, I learned that some of these same components first went into service at Barksdale AFB in 1938. The system was later transferred to the Shreveport Regional Airport for upper air observations from 1953-1975. The same equipment was then moved to Longview Texas for observations over the next two decades, and then back to the new NWS WFO office in Shreveport during the mid 90's for continued service through March of '06. Yes, even the floppies were set up during that last move, as they were part of the latest enhancement.

Finally, after many years of development, the NWS has integrated GPS technology into this next generation of instruments, termed RRS for Radiosonde Replacement System. Everyday, 92 upper-air stations around the country launch balloons carrying radiosondes simultaneously in order to take a snap shot so to speak of where jet streams are over the country, some reaching heights to 20 miles up. We are able to see how fast the jet stream cores are moving, how much moisture is present along with the latest temperatures structures of the atmosphere. All these and many more variables are usually sampled only twice a day. Although, extra obs are taken during high risk tornado threats or when large storms like hurricanes are in the Gulf of Mexico. And that is part of the reason why the official NWS forecast may change, sometimes drastically from the morning to evening issuance, because the latest of the two daily upper-air obs has shown a need for such adjustments in temperatures, winds or rain chances.

One of the first 5 stations in the country, your Shreveport NWS office was refitted with the new RRS in April. It took a federal team close to two weeks to integrate the change. Over the next 2 or 3 years, the remaining 75 or so upper-air stations across the country will be upgraded as well. When compared to the data we collected less than a year ago, the new RRS sondes collect 10 times more information on a single ascent. Plus the GPS technology, which utilizes as many as 10 low earth orbit satellites, is so much more accurate than the old approximation derived from a single radio signal; that it's like watching analog TV for 50 years and then seeing the same thing on a digital High Definition TV. This in turn allows for more precise inputs and detailed data into the computer models, which of course help meteorologist forecast the weather. The future of weather forecasting will continue to improve in both the short and long term, as more and more of the remaining stations across the country come on line with RRS.