PIREPS, Pilot Reports, are observations picked up by control towers at airports and air bases from pilots. If a weather observation reported by a pilot is of particular interest to forecasters, control tower personnel pass the information onto the National Weather Service ( NWS ). Pilot observations frequently include discussion on air turbulence and icing problems and sometimes include information on particularly large flocks of birds.
VERTICAL WIND PROFILER
A vertical wind profiler measures both wind speed and direction from 1,500 feet up through 55,000 feet in the atmosphere. Information is gathered by a microwave-generated beam. Currently a network of wind profilers is being used across the United States.
WSR-88D
WSR-88D (Weather Service Radar - 1988 Doppler) is the technical name for NEXRAD, commonly called Doppler radar. It not only detects areas of precipitation or intensity with great precision within a cloud, but also can determine the wind fields associated with a storm. In recent years, WSR-88D has been installed at many forecast sites around the US and has made forecasting a storm's track a more accurate task than in the past.
Besides enhanced imagery capabilities, satellites are now being equipped to take satellite soundings, profile pictures of the earth's atmosphere. For instance, GOES satellites contain infrared sensors that can provide temperature and moisture profiles across the North American continent via sounding devices. A new polar orbiting satellite called WINDSAT will include a laser device that will give more accurate worldwide wind information.
TELECONNECTIONS
Teleconnections refers to the fact that what goes on in one point of the world can be related to, or teleconnected to, the weather in another region. Telconnections are used by forecasters to determine what the weather might be as compared with past weather conditions at the same degree of longitude.
For example, if a forecaster observes a ridge or trough pattern that has held together at 70 degrees west longitude for a relatively long period (at least a couple of days), he or she can refer to teleconnection information. This will provide a generalized view of weather that has occurred elsewhere in the Northern Hemisphere in similar situations. COMPUTER MODELS
Computer models use mathematical equations to approximate or "model" the behavior of the real atmosphere. Actual atmospheric data is plugged into the equations with high-speed computers, which then produce analyses and forecasts.
The RUC, Rapid Update Cycle, is a new model which runs every three hours with forecasts out to 12 hours.
Short range computer models like the NGM (Nested Grid Model) or the ETA (the Greek letter Eta) are run twice a day and project weather conditions up to 48 hours into the future.
Long range models such as the MRF, ECMWF, and UKMET aid forecasters in predicting weather conditions three to ten days in advance.
SLOSH
SLOSH is an acronym for Sea, Lake and Overland Surge from Hurricanes. SLOSH models are used to estimate the vulnerability of any coastline areas where a hurricane may make landfall. It considers the intensity of the hurricane, the historical records of storm surges from storms at a particular location, the shape of the coastline and the slope of the ocean floor. Predictions are then made through computer analysis of this information.
POLAR ORBITING SATELLITES
Polar orbiting satellites complement geostationary satellites. Closely paralleling the earth at a height of approximately 500 miles in the atmosphere, they move in a longitudinal (north to south) direction over the North and South Poles, making a full rotation every ninety minutes.
While the polar orbiting satellites are moving in a north to south direction, the earth itself is rotating from west to east. Therefore, each time the satellite makes a rotation, it takes pictures farther west than before. Within a 24-hour period, the polar orbiting satellite has captured photographs of weather conditions throughout the world.
GOES
GOES, or Geostationary Operational Environmental Satellite, orbits the equator at about 22,300 miles above the earth's surface. Because GOES travels at the same speed as the earth's rotation, it remains stationary over the same location, taking pictures of weather patterns and sending them back to earth.
The GOES-8 and GOES-9 satellites take both visible (VIS) and infrared (IR) satellite pictures during the daylight hours. At night, however, GOES takes only infrared pictures because it is impossible to see cloud patterns without sunlight.
The infrared picture is an image produced by the heat radiation or radiance emitted by a cloud. You might say, then, that the GOES satellite is taking the cloud's temperature when it takes an infrared picture.
GOES satellites have special equipment that enables them to determine atmospheric moisture levels. The water vapor imagery photographed by a GOES satellite can be looped or "put into motion," showing areas and movement of moist and dry air.
Satellite soundings are now found on the new GOES satellites currently in orbit. Composed of infrared sensors, they competently provide forecasters with both temperature and moisture data at different levels of the atmosphere over North America.
The use of sounding lasers is another satellite technology that will soon be applied to the field of meteorology. This new application will include WINDSAT, a satellite that can take more accurate wind profiles of the atmosphere than have ever been possible to date. Now, instead of studying the troposphere from the ground up, meteorologists will be able to better study it from the top down.
RPG
A number of new radar products called Radar Products Generation (RPG) Subsystems will be available to weather forecasters in the near future. These products will use computerized graphic information to more easily predict severe storm situations and also provide data on wind direction and velocity.
