![]() In the same vein, Instant Snowfall is obviously invalid, so the site assumes you meant the smallest time period possible (for short and medium range GFS forecasts, this is 3-hr). ![]() For example, 6-hr CAPE makes no sense, so it is automatically changed to Instant CAPE before viewing. This is usually in the form of changing the time period. When invalid input is received that is very likely to be the result of a specific human error, the site automatically corrects that error. Some basic error-proofing is built into our site. I was looking at some maps and the time period automatically changed. A specially weighted average is then performed, and the result is multiplied by the precipitation over the requested time period to get the snowfall. To get around this, uses a proprietary algorithm inspired by the Evan Kuchera method to calculate instantaneous snowfall ratios. Unlike most variables we offer maps for, snowfall is not explicitly included in the model output provided by the NCEP server. The two maps on the home page are the highest temperature (Fahrenheit) in the next 24 hours and the expected precipitation (inches) in the next 24 hours, both according to the latest GFS run available. If the problem persists, make sure the map is listed in the Map List. The final map is usually generated several seconds later. The Status is updated whenever the first map is generated for a given forecast hour. Why does "Map Unavailable" show when I select a map from that hour? The "Status" area on the left shows that maps are available through a certain hour. The number before the "h" in the rightmost drop-down box is the number of hours into the future (after the initialization time, which can be seen in the leftmost drop-down box) that the forecast is valid for. "Total" refers to the value of a variable over the time period from initialization (hour 0) through the given forecast hour. refer to the value of a variable over a given time period. "Instant" stands for "instantaneous" and refers to the value of a variable at a given moment. 500mb refers to the altitude where the air pressure is exactly 500 millibars. 2m and 10m mean 2 and 10 meters above the ground respectively. Subtracting 1, 2, and 3 hours respectively from the result of this calculation will yield the time in Central, Mountain, and Pacific time. When Daylight Savings Time IS in effect, you can subtract 4 hours to get the time in Eastern Daylight Time. When Daylight Savings Time is NOT in effect, you can subtract 5 hours to get the time in Eastern Standard Time. government to refer to Universal Time (also known as Greenwich Mean Time). The "Z" stands for "Zulu" and is the notation used by the U.S. For instance, " 12Z" refers to 12:00 noon on February 1, 2011. Our maps present the date and time of a forecast as "YYYY-MM-DD HHZ". The values quoted on the home page represent all maps currently available to the general public by any means, free or paid. Of these, 940,620 maps (313,540 maps per day) are available for free on this website the rest are either only available with a subscription or are still in testing. For the CMC: We have by far the fastest-generating maps around, and we use 3-hourly data out to hour 240 instead of reducing the temporal resolution like many sites do.Įxactly how many maps are available on your site and app at any given time, and how many are generated every day?Īs of May 11, 2015, 2,729,486 maps are generated every day, and 19,106,402 maps are available at any given time. Our all-21-members maps display the mean alongside the members and are available for a variety of variables in the United States. For the GEFS: Our maps include minimum and maximum member maps, a feature not found on any other site. For the ECMWF: We offer every variable available in the free data set. For the RAP: We offer the full hourly output through hour 18 at 13-km resolution (as opposed to the 20-km resolution used by most other sites). We offer the full hourly NAM through hour 36, whereas other sites offer only the forecast hours divisible by 3. For the NAM: We use 12-km data as opposed to the 20-km or even 32-km data used by some other sites. ![]() The higher-resolution maps also generate much faster than the others because the files are available sooner from our data source. In addition, some surface maps, including snow depth, use the full native 0.117-degree data for the short range (through forecast hour 240). What sets apart from other sites, other than speed?įor the GFS: Many free sites use 0.5-degree or even 1.0-degree data, but we use the higher-resolution 0.25-degree data for all forecast hours (when referring to resolution, a lower number of degrees is better).
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