Real Time Weather
In 1985 Kansas had 3200 weather observations in 1995 there will be 86,600. The Aviation Weather Products Generator (AWPG) will brief pilots in the air with an accuracy of 5-10 miles and 5 minutes. 1000 airliners will be transmitting continuous weather data as they criss-cross the U.S. Airport controllers will have a three dimensional view of the weather and the approach to the runway. Virtual reality is here.
The first GOES satellite went up in 1975, six more have flown since. Two operate, east and west, most of the time. They give early warning and tracking for hurricanes and severe weather.
Geostationary Orbiting Environmental Satellite (GOES)
--Uses infrared photo to get cloud top temperatures. Darker color shows colder temperatures.
--Radar Composite
--Shows precipitation not clouds.
--Radar Summary Reports
--Radar images are summarized. May be vague but verify Radar Composite.
Forecast Reliability
For 12 hours good weather more correct than IFR
Poor weather in 3-4 hours at 80% accuracy
Distinct systems improve accuracy of forecast with tendency to under estimate severity
Cold front weather most difficult to forecast
Surface visibility forecast worse than ceiling
Cold front passage + 2 hours
Warm front passage + 5 hours
Warm front ceilings + 200' + 4 hours
Thunderstorms 1-2 hours with radar
Rain/snow + 5 hours
Weather briefing number
1-866-766-0820 for distant FSS
12-Hour Icing Forecast
http://adds.aviationweather.gov/icing
Changing to the Aviation Routine Weather Report (METAR) and Terminal Aerodrome Forecast (TAF) formats puts U.S. in step with rest of world in terms of weather format. In 1993 250 landing rights airports of the U. S. converted to the METAR code for international purposes. The rest of the world changed from the old METAR to the 'new'. By 1996 the U.S. will be completely METAR.
Attempt to demystify the new METAR/TAF weather formats at:
http://
Satellite Weather
Images reveal temperatures (height) coverage, movement, fronts. All images are dated.
Types
--Geostationary Operational Environmental Satellites (GOES) at 22,380 miles high. Picture distorted by curvature. --One large fixed area. Putting images into a film loop gives motion.
--GOES 8 is eastern US and GOES 9 is western --US. Visual images are photographic in appearance.
--Weather, clouds and surface are judged by ability to reflect light.
--Some interpretative conflicts exist and no cloud height information.
--Infra-red images are based upon cloud temperatures (heights).
--Thunderstorms are apparent as the brightest and coldest. Works as well at night as day.
--Water Vapor images show water vapor in levels of brightness.
Polar Orbiter Environmental Satellites (POES) at 3-500 miles. 900 mile wide strip-map.
Radiosonde (RADAT)
Rawinsonde DATa are upper air soundings via balloon. More than 1000 points that take soundings once at noon and again at midnight zulu time.
Type 1 called wind racks (Rawinsonde
Every 6 minutes gives wind direction and velocity
Type 2 Rags
Gives temperature and moisture and presented on constant pressure charts.
Balloons are soon to be replaced by wind profilers that detect winds by means of doppler radar and acoustic sounding. The profiler will every six minutes will take a variety of samples that will give winds aloft at 72 altitudes up to 53,000 feet. The computations are accurate to two knots. This system is not moisture dependent. Low level jet streams are checked to determine existence, extent of layers and velocity of wind shear.
Temperatures are measured by acoustic blasts at 850 hertz. The speed of the sound is measured by doppler radar as it varies in speed due to temperature differences. This works up to 18,000 feet. Balloons are to be used above this altitude.
Weather Radar
121 Weather Radars total in the U.S.
Present system uses 1950's era radar, which is down 20% of time. 40 newer radars have lower false alarm rate of bad weather The WSF-88D has 8 times the resolution, twice the range and 16 times the weather sensitivity. Predicting will be possible.
ARTCC radars do display precipitation and can on request give a pilot real-time (right now) information. Radar returns are known as Levels I, II, III, and IV. The National Weather Service uses six levels of thunderstorm intensity. ARTCC radar controllers have three weather display keys: WX-1, WX-2, and WX-3. WX-1 gives diagonal slashes on the screen to show moderate precipitation. WX-2 gives H Hs to show heavier areas and WX-3 shows both. The controllers are required to call every H as a Level VI thunderstorm. A pilot in need can request the controller to use the WX keys for assistance in weather avoidance. ARTCC will not volunteer this help you must ask for it.
New doppler radars (vary frequency much the way a train whistle does when passing) in the UHF serves as a wind profiling radar in combination with an acoustic transmitter enables the measurement of a temperature sounding. The maximum height of the doppler radar capability is greater than the acoustic pulse because the acoustic pulse is moved out of the radar beam.
The new weather radar will give coverage to 10,000' from 175 sites and no gaps east of Cheyenne. 40% of the radar weather coverage will be in new areas. System works by showing air motion and will be given to other ATC facilities. Some day into the cockpit? Another system will give 45 airports severe storm information and can be scan-specific to most important runways. Accuracy will vary from 60 to 80%.
New systems are going to be able to derive (predict) data. Present system has more data than can be processed, interpreted or distributed. Record the altitude of each )degreeC isotherm. Green on color charts indicate dewpoint spread of less than 5°. Icing exists where shaded area cut by 0 degrees to -10 degrees isotherms. 500 millibar winds (128,000') are usually emphasized because they are removed from earth surface influences.
Icing forecasts take over when there are no PIREPS given. When you give weather PIREPS, so so every 15 minutes so they can be charted as they change. There is now a chart being created based only on PIREPS.
When asking radar for weather you must first find out if they have weather detection capability. The radio procedure is to say, "Give me the setup of all Level-2 and above weather and vectors around it."
SLC 1400 RADAT 70 M 030 066 165 /3
SID UTC rh rh y y y
time refers
to mid y Y's in 100's Additional
Station relative of feet of isotherms
identifier humidity 0° isotherms crossed
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