What Does It All Mean?

| January 8, 2011 @ 10:00 am | 440 Replies

I get many questions about the terms we use in our daily discussions… and we should mention, we do these every day throughout the year, not just during snow or severe weather. Here is a look at the terms you might read here…

Critical Thickness (540 line): Thickness is the vertical distance between two isobaric surfaces, which is often proportional to the temperature of that layer. As such, empirical studies have shown that certain values of differing thickness have shown some skill in differentiating between rain or snow:
1000-500 mb (5400 m)
1000-700 mb (2840 m)
1000-850 mb (1300 m)
850-700 mb (1540 m)

GFS: Global Forecast System model. Run four times a day (00, 06, 12, 18 UTC) and produces forecasts up to 16 days in advance, but with decreasing spatial and temporal resolution over time. The model is run in two parts: the first part has a higher resolution and goes out to 180 hours (7 days) in the future, the second part runs from 180 to 384 hours (16 days) at a lower resolution. The resolution of the model varies in each part of the model: horizontally, it divides the surface of the earth into 35 or 70 kilometre grid squares; vertically, it divides the atmosphere into 64 layers and temporally, it produces a forecast for every 3rd hour for the first 180 hours, after that they are produced for every 12th hour.

NAM: North American Mesoscale model. It technically is the Weather Research and Forecasting Non-hydrostatic Mesoscale Model (WRF-NMM), but it is run as the NAM. The model is run four times a day (00, 06, 12, 18 UTC) out to 84 hours. It is currently run with 12 km horizontal resolution and with 1 hour temporal resolution, providing finer detail than other operational forecast models.

RPM: Rapid Precision Mesoscale model. A numerical weather prediction system based on the Advanced Research Weather Research and Forecast system (WRF-ARW). RPM generates forecasts out to 24 hours with updates every 3 hours in the United States and every 6 hours outside the United States. Precipitation forecasts are calculated from half-hourly instantaneous precipitation forecasts output by RPM. RPM model output is not available to the pubic; but we have full access and use it extensively in our forecast products.

Z: When you see a time like 12Z, 00Z, 06Z, etc… Z simply stands for Universal Coordinated Time, the time standard by which the world regulates clocks and time. It is equivalent to GMT, or Greenwich Mean Time. This is six hours ahead of local time, but when we are on Daylight Saving Time is is 5 hours ahead of us. For example, at this time of the year, 00Z is 6:00 p.m. Alabama time. 12Z is 6:00 a.m. Alabama time.

500 mb chart: This is one of the mandatory levels in the atmosphere; they are constant-pressure levels for which a complete evaluation of data derived from upper-air observations is required. Currently the mandatory pressure levels are 1000 mb, 850 mb, 700 mb, 500 mb, 400 mb, 300 mb, 200 mb, 150 mb, 100 mb, 50 mb, 30 mb, 20 mb, 10 mb, 7 mb, 5 mb, 3 mb, 2 mb, and 1 mb. The radiosonde code has specific blocks reserved for these data. 500 mb is usually about 18,000-20,000 feet off the ground. When we show a 500 mb chart, the height contours you see are in decameters, and represent the altitude where the pressure is 500 mb.

I will add more to this list when time allows in coming weeks… and we will keep this in the category “Meteorology 101″… so you can access it when you need it!

Comments

Powered by Facebook Comments

Tags:

Category: Met 101/Weather History

About the Author ()

James Spann is one of the most recognized and trusted television meteorologists in the industry. He holds the AMS CCM designation and television seals from the AMS and NWA. He is a past winner of the Broadcast Meteorologist of the Year from both professional organizations.

Comments (440)

Trackback URL | Comments RSS Feed

Sites That Link to this Post

  1. My Homepage | November 5, 2017
  2. Boone Jenner Jersey | November 5, 2017
  3. Britton Colquitt Jersey | November 6, 2017
  4. Kirk Cousins Jersey | November 6, 2017
  5. Javier Calle New York City Jersey UK | November 6, 2017
  6. Willson Contreras Jersey | November 6, 2017
  7. Gabriel Jersey | November 6, 2017
  8. Jese Jersey | November 6, 2017
  9. Jordan Adams Jersey | November 6, 2017
  10. Joe Staley Jersey UK | November 6, 2017
  11. Riley Nash Jersey UK | November 7, 2017
  12. Tim McCarver Jersey UK | November 7, 2017
  13. fallout 4 cheat codes | November 7, 2017
  14. Cheap Jerseys Free Shipping | November 7, 2017
  15. Ray Allen Jersey UK | November 8, 2017
  16. Dana Barros Jersey | November 8, 2017
  17. http://www.ncaasportsshop.com/Florida-State-Seminoles-Javien-Elliott-Jersey/ | November 8, 2017
  18. Tampa Bay Rays Jersey | November 8, 2017
  19. Peter Forsberg Jersey | November 10, 2017
  20. Logan Forsythe Jersey | November 10, 2017
  21. Kobe Bryant Jersey | November 11, 2017
  22. Jake Elliott Women's Jersey | November 11, 2017
  23. shaq thompson jersey | November 14, 2017
  24. Rodney Gunter Jersey | November 15, 2017
  25. nfl jerseys china | November 16, 2017
  26. nike steelers jersey | November 17, 2017
  27. cheap nike nfl jerseys china | November 18, 2017
  28. cheap nfl replica jerseys | November 19, 2017
  29. Cody Ceci Jersey | November 20, 2017
  30. where can i buy nfl jerseys cheap | November 20, 2017
  31. sscn.bkn.go.id | November 20, 2017
  32. Harrison Heath Orlando City Jersey | November 20, 2017
  33. cheap nfl nike elite jerseys | November 21, 2017
  34. cheap replica nfl jerseys | November 22, 2017
  35. women's nfl jerseys cheap | November 25, 2017
  36. Robinson Cano Jersey | November 26, 2017
  37. Cheap NFL Jerseys Sale | November 26, 2017
  38. iraqi coehuman | November 29, 2017
  39. Cheap Jerseys Online | December 2, 2017
  40. http://www.sportsnflshop.com/Oakland-Raiders-Tim-Brown-Jersey-Sale/ | December 9, 2017

Leave a Reply

You must be logged in to post a comment.