1. ABC’s of weather forecasting NOAA/NATIONAL WEATHER SERVICE WFO BALTIMORE / WASHINGTON OPEN HOUSE – APRIL 30-MAY 1, 2016 RAY MARTIN –– Lead Forecaster

2. THE TOPICS  Forecast tools  Forecast process  Elements of a forecast  Forecast products

3. Forecast tools  Current and recent weather observations  Simulations of the atmosphere (a.k.a., computer models)  Forecaster experience

4. Observations  Satellite, radar, surface obs, upper air

5. Computer models  Computer guidance – numerous models in several formats

6. Forecast process  To truly get a good handle on how the atmosphere is behaving, one must start with a wide view of what is happening and expected to happen  From there, one needs to slowly “zero in” on the target area and time period  Otherwise, you might miss something, and get a surprise later on!

7. Wide view - hemispheric  By “Hemispheric” we mean the Northern Hemisphere  Looking for the positions of the large-scale ridges and troughs and their expected changes in time  Large scale features dictate smaller scale ones!

8. Narrowing in – synoptic scale  Next step is to identify individual disturbances… the kind associated with frontal low pressure systems  Their movement and evolution influence yet smaller scale features!

9. Close look - Mesoscale  Local variation (scale of miles) dictates what effects people actually feel  Outflow boundaries, sea breeze fronts, and terrain circulations are factors here  Thunderstorms are the best examples, but even large winter storms can have big variations within a few miles

10. Elements of a forecast Your basic forecast consists of the following elements:  Temperature  Humidity  Cloud cover  Precipitation  Wind  Obscurations to visibility

11. Temperature  Temperature forecasts include day-time maximum, night-time minimum, and hourly values  Forecast is influenced by sun angle/time of year cloud cover precip, or lack thereof advection (movement) of air masses, both at the surface and upper levels

12. Humidity  Humidity forecasts focus on hourly values, though fire weather requires daily maximum and minimum expectations  Forecast is influenced by precip or lack thereof advection (movement) of air masses vertical mixing in the atmosphere

13. Cloud cover  Cloud cover is forecast in discrete hourly values as a percent of coverage For aviation, we also forecast the height of the clouds above ground  Cloud cover forecasts depend on available moisture a source of lift at the same altitude as the moisture

14. precipitation  Precipitation forecasts consist of probability, amount and type, and possibility of thunder  The forecast of precipitation location and amount depends on moisture lift overall horizontal motion in the atmosphere  Precipitation type depends on temperatures near the ground temperatures aloft

15. wind  Wind speeds and directions are forecast hourly  Unlike the other elements, wind forecasts are intended to be representative of values at 33 feet in an open field… which is not quite what most people experience!  The forecast depends upon surface features affecting air friction pressure gradient orientation and intensity extent of vertical mixing

16. Obscurations to visibility  Visibility is forecast as an hourly value  Fog, haze, and dust are the main causes of reduced visibility  The forecast depends upon Stable moist atmosphere promoting fog development or mist High humidity and particulates combining to cause haze Fires

17. Forecast products Hazards Public Aviation Hydrology Marine Tides Fire weather

18. hazards  Severe thunderstorm and tornado watches and warnings  Flood watches and warnings (Flash, River, Aerial)  Hurricane and tropical storm watches and warnings  Fire weather watches and red flag warnings  Winter storm watches, warnings and winter weather advisories  Coastal flood watches, warnings and advisories  High wind watches, warnings and wind advisories  Excessive heat watches, warnings and heat advisories  Wind chill watches, warnings and advisories  Freeze watches, warnings and frost advisories  Fog advisories

19. Public forecasts  Zone forecast product  Point-and-click  Graphics

20. aviation  Terminal Aerodrome Forecasts (TAFs)

21. hydrology  River level forecasts

22. marine  Coastal waters forecast  Point-and-click  Graphical forecasts

23. tides  Total water forecasts

24. Fire weather  Fire weather forecasts  Spot forecasts

25. So where can you find all this great stuff? www.weather.gov /washington Questions? ray.martin@noaa.gov