Accessing and Interpreting Web-based Weather Data Clinton Rockey National Weather Service Portland, Oregon

NOAA Weather Online Aviation Digital Data Service (ADDs) Aviation Digital Data Service (ADDs) Aviation Weather Center (AWC) Aviation Weather Center (AWC) National Weather Service (NWS) National Weather Service (NWS) Your Local NWS Office Your Local NWS Office

A common question I have heard from pilots is, “How can I learn more about the weather?” There really aren’t any stand alone courses out there aimed at pilots, and Taking Atmospheric Sciences 101 from a university isn’t a very helpful option.

A zero cost way for YOU to do it (though it will take time and patience) ….may be to… “AFD” it. Area Forecast Discussion Discusses the current weather forecast, NWS Meteorologist’s view of the weather, Issued 4 times/day.

1) Read and digest the AFD. Part 1 – where you can find the AFD 2) Compare this to data on the Internet. Forecast Charts Satellite Imagery RADAR Imagery Part 2 – Interpreting Weather Charts So how do you learn more by ‘AFD’ing it? 3) Repeat… Part 3 – this is YOU.

How Do I Start? Read DiscussionsRead Discussions SatelliteSatellite Troughs and Ridges? Troughs and Ridges? Where are the Fronts? Where are the Fronts? Which way are these moving? Which way are these moving? Model GraphicsModel Graphics

Visible Images When Sun is up, clouds reflect the sunlight. So, clouds are visible. But, when sun goes down, what do we do? Can see land features Also, Can Infer Low Level Winds

Details Of Visible Images Typical Summer Afternoon

Visible Image Summary PROs: Shows topographic features Shows best detail of cloud features CONs: Not available at night See tops of the clouds only (can not tell if precipitation occurring) Can infer low to mid-level wind flow May be difficult to see clouds over snow covered terrain or layers of clouds.

Warmer the clouds, darker the shading. Colder clouds tops are white, and may be enhanced with color Cold Front, with Rain Cold Clear Air L

L 22 FEB 2007, 1 pm PST H L L

IR Image Summary PROs: Shows cold and warm advection Good for determining areas of increasing or decreasing precipitation CONs: Best for night time use, but day is good Really cold air can often be mistaken for precipitation areas Good for showing developing or weakening storms

Water Vapor Image Moisture shows as gray/green areas. Dry air indicated by dark areas. Developing low, Along a front (rising moist air) Dry, sinking air L

L 22 FEB 2007, 1 pm PST L L H L H

Water Vapor Image Summary PROs: Shows moisture/dry air advection (dry areas are candidates for fog and low level inversions) Good for detecting disturbances in the upper flow that may enhance/weaken low level inversions. CONs: Hard to determine areas of precipitation as same are could just be clouds Good for showing developing or weakening storms and fronts

NOAASurfaceGraphics These are basic graphics, mostly focused on fronts and simple weather over the next several days. Best Use: Get idea of fronts And where they will Over the next 48 hrs.

850 mb ~ 5k 700 mb ~ 10k 500 mb ~ 18k 300 mb ~ 30kNOAAModelGraphics Charts use a number that reflects the pressure height. Examples: 500 mb Heights 300 mb Winds 850 mb Humidity

Think of Low as a depression or valley (we call them troughs). Troughs = Lower Pressure. And a High as a mountain or ridge. Ridges = Higher Pressure.

This is another 500 mb (millibar) chart This is a big long-wave trough This is a small short-wave trough

More points… 5) Winds flow parallel to the lines of constant height. (True for 700 mb and above). 6) The strength of the winds is proportional to the distance between the lines. Strong winds = lines close together Weaker winds = lines further apart.

Use of Big 5 Model Charts 300 mb 500 mb 700 mb 850 mb Surface Jet Stream-location & strength Troughs, Ridges, and short waves Vertical lift and RH = Precipitation Temperature, often for rain/snow line. Also, gives 5000 ft level winds Locate Fronts, Surface Highs/Lows. Surface Winds, based on gradients

300mbChart (30k ft) Best Use: Location and Movement of Jet Stream. Remember, Jet Stream steers the Highs and Lows.

500mbChart (22k ft) Best Use: Location and Movement Ridges and Troughs. Remember, Also Look for short waves, as they create the weather.

700mbChart (10k ft) Best Use: Identify areas of precipitation. Remember, stronger lift & more RH, the better the threat of precipitation

850mbChart ( 5k ft ) Best Use: Location and movement of cold & warm air masses. Look for the 0 deg line. +1 deg or colder often results in snow on Cascades.

SFC(surface)Chart ( 5k ft ) Best Use: Location & Movement SFC Lows & Highs, clouds & sfc winds. Remember, closer the lines (or gradient), the stronger the winds.

NOAA’s ADDs Specialized Graphics These are specialized graphics, produced by the National Aviation Weather Center. Icing Potential available for different altitudes, with probability for severe icing. Best Use: Short-term planning. Freezing Level & Icing Potential

Questions?