July 2003 National Weather Service Volume 2, Number 2 Aircraft Weather Observations Improve Forecasts In this Issue: By Richard Mamrosh, Forecaster the NWS and the Federal Aviation NWS, Green Bay, WI Administration use of this data in NWS warning and forecast services. In addition to providing fast and An average of more than 150,000 Commercial Airline safe transportation, many commercial reports are available daily, and Data Boosts jet aircraft report weather data that is supplement upper air data from pi- Forecast Accuracy 1 helping the National Weather Service lot reports (PIREPS), weather bal- (NWS) produce better forecasts and loons and satellites. The information warnings. flows to the National Center for En- Automated weather reports from vironmental Prediction, where it is Enhance PIREPs By these aircraft have contributed to a ingested by NWS computer models. Getting More significant improvement in forecast The data also goes to the Forecast Sys- From Your GPS 3 accuracy over the past 10 years. These tems Laboratory, where it is displayed wind and temperature reports are au- on an interactive Web page. See Fig- tomatically transmitted from selected ure 1, below. Changing Times, aircraft of six major airlines, and have While most aircraft only report lead to improvements in aviation, temperature and wind, an increasing Changing Products, public and marine weather forecasts. number of aircraft also report turbu- Revisiting the Lifted American, Delta, Federal Express, lence and icing. Humidity sensors Index Chart 6 Northwest, United, and United Parcel were installed on a few dozen aircraft Service have agreements permitting in the late 1990s as part of an experi- Managing Editor: Michael Graf Contributing Editor: Craig Sanders Editor: [email protected] Mission Statement To enhance aviation safety by increasing the pilot’s knowledge of weather systems and processes and National Weather Service products and services. Figure 1: Example of data for three hour period on July 19, 2003 1 Importance and Future of Aircraft vice meteorologists at Air Route Traf- fic Control Centers routinely use Weather Reports ACARS to locate jet streams that cause dangerous turbulence. This automated data, Lyle Alexander, meteorologist at Aircraft Communications Ad- the Indianapolis CWSU says, “We had dressing and Reporting Sys- some turbulence in the area, and the tem (ACARS) or Meteorologi- ACARS data helped me to mark off cal Data Collection and Re- the areas where the turbulence was porting System (MDCRS), occurring. The models gave me an has been used as input to the idea where it might be, but the numerical weather predic- ACARS helped me to fine tune it, re- tion models for the past 10 sulting in a more accurate forecast.” Figure 2: Navy bi-plane with meteorograph on years. In one of the models, Mike Foley, a dispatcher with starboard wing strut taking meteorological aircraft wind data was found Delta Airlines adds, “I use ACARS data measurements of pressure, temperature, and to be even more important to provide real time turbulence in- humidity. than radiosondes. When air formation to our flight crews. Used travel was halted for several in conjunction with real time PIREPS, ment that will be expanded later this days after September 11, 2001, the it generally makes the cause and lo- year. Humidity is highly variable in chief short-range NWS computer cation of the turbulence much easier the atmosphere and difficult to mea- model showed a dramatic reduction to find.” sure; however it is vital to accurate in forecast skill. Figure 3 shows the tremendous forecasts of precipitation and icing. The data is used by NWS and air- amount of real-time wind data avail- line meteorologists to forecast avia- able to NWS, airline and FAA meteo- tion hazards such as turbulence, ic- Brief History: rologists for a typical 3-hour period ing, fog and low level wind shear. on an average day. Aircraft Weather Data This data is also used to forecast high The data on this day shows wind events, snow and ice storms, se- an upper level low near Cleveland In 1919, The NWS began paying vere thunderstorms, and other phe- and winds of 50 to 100 knots on ei- pilots to fly piston engine aircraft nomena. NWS Center Weather Ser- ther side of the upper low. with weather instruments strapped on the wings of their biplanes. NWS paid pilots only if they reached an altitude of more than 13,500 feet; pilots received a bonus for every thousand feet thereafter. The lack of pressurized aircraft, navigational aids or aviation weather forecasts made the task extremely dangerous. These flights were discontinued in 1940 with the advent of radio- sondes, weather instruments carried aloft by balloons. PIREPS continued to supply important weather reports of conditions above the ground. In the 1960s, these reports appeared in numerical weather prediction mod- els. By the 1980s, datalink systems allowed meteorological data to be re- trieved automatically from an increas- ing number of aircraft. Currently, about 1,500 commercial aircraft transmit weather information. This number is likely to increase further as regional, corporate, and some gen- Figure 3: Example of winds from approx. 20,000 to 45,000 feet MSL for the three eral aviation aircraft install datalink hour period ending 2000 UTC June 20, 2003 systems. 2 Weather data from aircraft will become even more important in the Enhance PIREPs By Getting future as meteorologists attempt to make forecasts with greater accuracy More from Your GPS and detail. Radiosondes are routinely launched twice a day in the morning By Craig Sanders and evenings, and are roughly 200 Lead Forecaster, NWS Duluth miles apart. This schedule is often not sufficient to resolve weather phe- Some commercial aircraft send as monitor ground speed, time en nomenon such as thunderstorms, pilot reports (PIREPs) through the route, and estimated time of arrival. icing and turbulence. ACARS data link. They can send any On an often overlooked page or Experiments are now being con- combination of computed wind corner of the display in many GPS ducted to determine whether it is speed, temperature, turbulence, and systems, is valuable data many pilots cost effective to install weather instru- humidity for input into the NWS may not consider important: com- ments and datalink systems on re- Rapid Update Cycle (RUC) computer puted wind speed and direction. gional, corporate and general avia- model. Getting a little black box like Your GPS computes it every few sec- tion aircraft. that for your GA or corporate aircraft onds. Why not use it? One such experiment called Tro- requires a bit more than pocket The NWS supercomputers crank pospheric Airborne Meteorological change. out a wide variety of maps and Data Report (TAMDAR) is a joint The good news is that you don’t printed data specifically for aviation. NASA/FAA/NWS project to be con- need that particular technology to The Aviation Weather Center (AWC) ducted later this year. The idea is to serve your fellow pilots well. You can displays many of these on its Web install relatively inexpensive sensors be of great service with the GPS box site. One of these data types is the that will measure temperature, hu- that’s already there. Most GPS boxes FD winds aloft tables, which have midity, wind, turbulence and icing on enable you to set up flight plans, been around for decades. These table turboprop aircraft for a regional air- routes, approaches and holds, as well are available at the AWC web site at: line. If successful, similar sensors http://aviationweather.gov/. could be used on corporate and gen- In your training days, you prob- eral aviation aircraft. ably worked out tedious, but neces- sary navigation and aircraft perfor- Current Data Access mance problems on an E6B whiz wheel. Some problems involved cal- Due to proprietary consider- culating headings for a flight, given ations, basic aircraft weather data is the winds aloft forecast. available only to the participating air- You had to use the backside of lines, the FAA, and NWS. Airlines have the computer (see Figure 1) with its historically borne some of the costs round plastic plotting window, azi- associated with transmitting the data. muth ring, sliding airspeed and You can still benefit from this data ground speed scales. With a pencil, source by accessing a numerical you drew lines and triangles repre- model called the Rapid Update Cycle senting those speeds and directions, at http://ruc. fsl.noaa.gov. and you rotated the ring and the win- The model is run every 3 hours dow to configure the computer to with the latest data and upper level represent heading and course. winds, pressure patterns, and fore- The process was a method to get cast vertical soundings of the atmo- you to visualize and understand the sphere can be displayed at many U.S. trigonometry of the problem. It was airports. tedious and careful work to do at a Accurate aviation forecasts table in the FBO. To plot and calcu- require in-flight data from both light late the data on an E6B in even light single engine aircraft and jumbo jets! Figure 1: The legacy E6B flight turbulence was about as easy as try- Automated aircraft weather data and computer's heading and speed side ing to stuff a porcupine into a can PIREPs can be combined to give the can solve almost any aviation problem backwards. meteorologist the information for dealing with speed and direction. If only you had known during making make detailed and accurate It can compute actual winds in flight the preflight prep what the winds forecasts of aviation hazardous. just like modern GPS equipment. actually were, instead of relying on 3 Figure 2: The AWC homepage contains a link to FD Winds and Temperatures aloft.