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Frequently Asked Questions

1. What is UTC or Z time, and how do I convert it to my local time?

2. Where can I find forecasts beyond 7 days?

3. Where can I find historical or climatological weather data?

4. How can I obtain past forecasts or analyses produced at the WPC?

5. How do I decipher the contractions/abbreviations used in your discussions?

6. How do I interpret the symbols and station model plots on your analysis and
forecast charts?


7. For what time is the "current forecast" on your home page valid?

8. Are the 5-day QPF and day 1, 2, and 3 QPFs based on the same guidance?

9. What do the colors represent on your satellite images?

10. Why has the domain for your surface analysis been reduced?

11. Where can I get information about a career in meteorology?

12. Where can I find copies of the Daily Weather Map prior to 2003 online?


What is UTC or Z time, and how do I convert it to my local time?

UTC literally stands for Universal Time Coordinated (though it is typically referred to as Coordinated Universal Time) and is the standard time common to every place in the world.  It is also known as Greenwich Mean Time (GMT) and Zulu (Z).  UTC is defined as the time at longitude 0 degrees, the prime meridian.  This is the longitudinal line that separates the Eastern and Western Hemispheres, and happens to pass through the Greenwich Observatory outside of London, England.  All of our forecast products and the computer models that provide us guidance are based on this universal time zone.

When you see 12 UTC or 1200 UTC or 12Z (all are the same and depend on forecaster preference), it refers to noon at Greenwich.  00 UTC or 00Z is midnight Greenwich time.  Translating this to your time zone depends on where you live.  Below is a table that provides some UTC times and their conversion to the four time zones over the lower 48 for standard time.

STANDARD TIME

 
 
PACIFIC
MOUNTAIN
CENTRAL
EASTERN
0000Z/UTC
4:00 PM
5:00 PM
6:00 PM
7:00 PM
0300
7:00 PM
8:00 PM
9:00 PM
10:00 PM
0600
10:00 PM
11:00 PM
Midnight
1:00 AM
0900
1:00 AM
2:00 AM
3:00 AM
4:00 AM
1200
4:00 AM
5:00 AM
6:00 AM
7:00 AM
1500
7:00 AM
8:00 AM
9:00 AM
10:00 AM
1800
10:00 AM
11:00 AM
Noon
1:00 PM
2100
1:00 PM
2:00 PM
3:00 PM
4:00 PM

So, for example, if we write 12Z Friday, itíll be 7:00 a.m. Eastern Standard Time (EST) and 4:00 a.m. Pacific.  If itís 00Z Friday, it will be 7:00 p.m. Thursday EST and 4:00 p.m. Thursday Pacific.

The table below is for daylight time.

DAYLIGHT TIME

 
  PACIFIC MOUNTAIN CENTRAL EASTERN
0000Z/UTC
5:00 PM
6:00 PM
7:00 PM
8:00 PM
0300
8:00 PM
9:00 PM
10:00 PM
11:00 PM
0600
11:00 PM
Midnight
1:00 AM
2:00 AM
0900
2:00 AM
3:00 AM
4:00 AM
5:00 AM
1200
5:00 AM
6:00 AM
7:00 AM
8:00 AM
1500
8:00 AM
9:00 AM
10:00 AM
11:00 AM
1800
11:00 AM
Noon
1:00 PM
2:00 PM
2100
2:00 PM
3:00 PM
4:00 PM
5:00 PM

 
Where can I find forecasts beyond 7 days?

The Climate Prediction Center (CPC) is the branch of NOAA's National Weather Service (NWS) responsible for issuing forecasts beyond 7 days.   Their Outlooks page provides links to each of their forecast products, including the 6-10 day and 8-14 day forecasts, along with monthly and seasonal forecasts.  Seasonal forecasts are produced in 3-month intervals and extend out to over one year into the future.  So, if you are looking for a forecast for the upcoming winter (December-January-February) or summer (June-July-August), simply click on the appropriate link.  If you have any questions regarding their forecasts, please click here to e-mail them directly.

Where can I find historical or climatological weather data?

If you are looking for past weather information for a particular location, you have a couple of options.  The first is directly visiting the web site of NOAA's NWS Weather Forecast Office (WFO) that serves the desired location.  You can access any of the local offices through the NWS Home Page.  If you are not sure which is the correct WFO, type the city or town name in the white box located in the upper left-hand part of their home page and click GO.

If you are unable to find information from the local office, the National Climatic Data Center has a very comprehensive collection of data and will likely have whatever you need.  You can access them through the link above or call them at 828-271-4800.

How can I obtain past forecasts or analyses produced at the WPC?

Due to the large number of products issued and limited space, there are only a few products residing on our site that are more than one day old.  They are:

How do I decipher the contractions/abbreviations used in your discussions?

We have a link on our site, Explanation of Contractions, that provides definitions for most of the contractions or abbreviations used in our discussions.  Included in this list are the two-letter state and territory abbreviations and contractions for the numerical models our forecasters utilize.

How do I interpret the symbols and station model plots on your analysis and forecast charts?

All of this information can be found by clicking on the links below.
  • Surface Fronts describes the fronts depicted on our analysis and forecast maps, along with how to interpret the 3-letter coding adjacent to the frontal boundary.  
  • Precipitation Areas explains the weather symbols and the difference between shaded and unshaded precipitation areas used on our short range (1-2 day) forecasts.  
  • Station Plots provides interpretation of the station models depicted on our surface analysis and observation charts.
For what time is the "today's forecast" on your home page valid?

The valid time for this product varies slightly depending on the weather feature for which you are interested.
  • Daytime surface features (highs, lows, and fronts) represent a forecast valid at 1800 UTC (1:00 p.m. EST).
  • The general precipitation areas depicted are valid for a 12-hour period during the current day, from 1200 UTC (7:00 a.m. EST) through 0000 UTC (7:00 p.m. EST).
  • Severe weather and flash flooding forecasts are valid for the 24-hour period starting at 1200 UTC of the current day
  • Heavy snow and ice forecasts are usually valid from for the 12-hour period during the current day (from 1200 UTC to 0000 UTC), however, if warranted, may extend an additional 12 hours to 1200 UTC of the following day.
Are the 5-day QPF and day 1, 2, and 3 QPFs based on the same guidance?

No. The 5-day QPF issued by our medium-range forecasters is based primarily on the 0000 UTC and 0600 UTC numerical model runs, with a quick glance at the 1200 UTC runs. The forecaster prepares a forecast for days 4-5, then adds the days 1-3 QPF issued at about 1000 UTC to get a 5-day forecast. All of this is based on 0000 and 0600 UTC model guidance. The forecaster then adjusts the 5-day total based on quick looka the 1200 UTC model output.

What do the colors represent on your satellite images?

The infrared satellite imagery on our web site is "enhanced", which means that the image is modified using a color scheme in order to bring out details in the cloud patterns. The various colors are determined by the amount of energy, translated into temperature, that the satellite is sensing. The image below represents the enhancement curve that is used in all of the satellite imagery on our site. The numbers correspond to the temperature in degrees Celsius that is associated with colors on the enhancement curve. The darker colors on the left side of the represent warmer temperatures, while those to the right are colder. Since the atmosphere cools with height, the areas in yellow, blue, red or green usually indicate progressively higher (therefore colder) cloud tops. The shades of light gray show low cloud tops, while the dark areas on the left side of the curve typically show that the skies are clear and the infrared imagery is actually measuring the temperature of the land or ocean surface. However, infrared images can be misleading in the winter under a very cold air mass. If the surface temperature is, for example, around -25 degrees Celsius (-13 degrees Fahrenheit, not unusual for December-February in the northern U.S. and Canada), the dark yellow image will suggest cloud cover is present even if it is completely clear. In these cases the image needs to be interpreted with caution.

WPC Infrared Satellite Enhancement Curve

Why has the domain for your surface analysis been reduced?

The previous, larger area (covering more of the Atlantic and Pacific Oceans) was defined at time when the North American analysis was distributed by facsimile and only one chart could be sent for each analysis time and this chart needed to meet the needs of a wide variety of users. Most users of NWS products were able to receive only the WPC analysis and it needed to cover a wide area to meet the needs of all users.  NCEP now has three centers preparing surface analysis charts over much of the Northern Hemisphere and all are available to all users.  The oceanic areas eliminated from the WPC analysis are better served by the Ocean Prediction Center (OPC) and the National Hurricane Center (NHC).  Their later deadlines allow more observational data to be incorporated into OPCs' and NHCs' analyses, resulting in a more accurate product. Please see changes to the North American surface analysis for more information.

Where can I get information about a career in meteorology?

Below are a few links that provide a good introduction into the field of meteorology, including educational requirements and career opportunities.
  • A Career Guide for the Atmospheric Sciences was published by the American Meteorology Society (AMS) in 2000.  This site provides a good overview of the educational requirements (including links to colleges/universities that offer degrees) and details the different career paths that exist in the field of meteorology.  This is probably the most comprehensive source of information available.
  • The National Severe Storms Laboratory provides a shorter, less detailed description of education requirements and career opportunities.
  • Challenges of Our Changing Atmosphere is a more dated (1993) publication by the AMS, but is still an excellent resource.
If you are interested in current employment opportunities in the NWS or NOAA, visit  http://www.jobs.doc.gov/ to begin your search.  A good source for employment opportunities outside of the federal government is the National Weather Association's Job Corner.

Where can I find copies of the Daily Weather Map prior to 2003 online?

Daily Weather Maps from 1872 through 2002 are available at the NOAA Library web site at http://docs.lib.noaa.gov/rescue/dwm/data_rescue_daily_weather_maps.html.   Viewing the Daily Weather Maps requires the free DjVu Browser plug-in. There is a link at the site for downloading.


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Page last modified: Tuesday, 05-Mar-2013 13:08:41 UTC