Weather forecast maps by GFS
The weather maps on this page are created and owned by firenzemeteo.it. You can use them on other websites
or on publications always quoting firenzemeteo.it as a reference. It is forbidden to modify the maps.
VERSIONE ITALIANA: CLICCA QUI
To see instead the GFS ANALYSIS MAP ARCHIVE from 2013 to today click on the link.
Notes on GFS forecast maps
The Global Forecast System (GFS) is a National Centers for Environmental Prediction (NCEP)
weather forecast model that generates data for dozens of atmospheric and land-soil variables,
including temperatures, winds, precipitation, soil moisture, and atmospheric ozone concentration.
The system couples four separate models (atmosphere, ocean model, land/soil model, and sea ice) that work
together to accurately depict weather conditions.
GFS is a global model with a base horizontal resolution of 0.25° (28 kilometers) between grid points. The GFS is run 4 times a day, the temporal resolution covers analysis and forecasts out to 16 days.
GFS Central Italy: CAPE [J/kg] e Lifted Index [°C]
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These maps show the CAPE (Convective Available Potential Energy, in J/Kg) and the Lifted Index (in °C).
The CAPE is an atmospheric instability index that measures the amount of energy available for convection. The higher this value, the more energy a particle of air has to rise along the vertical. For example, a CAPE of 1000 J/kg means that each kg of air receives a total energy of 1000 Joules during a free ascent. The following table shows the relationship between CAPE values and the storms:
|CAPE [J/Kg]||Risk of Thunderstorms|
|500÷1000||Risk of isolated thunderstorms|
|1000÷2000||Fairly probable thunderstorms|
|>2000||Strong thunderstorms quite likely (risk of tornadoes)|
The Lifted Index is an atmospheric instability index obtained by computing the temperature that air near the ground would have if it were lifted to 500 hPa and comparing that computed temperature to the actual temperature at that level. When the value is positive, the atmosphere (at the respective height) is stable and when the value is negative, the atmosphere is unstable. The following table shows the relationship between Lifted Index values and the storms:
|LIFTED INDEX [°C]||Risk of Thunderstorms|
|0÷2||Risk of isolated thunderstorms|
|-2÷0||Fairly probable thunderstorms|
|-4÷-2||Risk of severe thunderstorms|
|<-6||Strong thunderstorms quite likely (risk of tornadoes)|
On the top left is shown the UTC initialization time. UTC time is indicated with Z letter (Zulu Time). On the top right is shown the UTC forecast time.
The maps at 00Z, 06Z, 12Z and 18Z are updated respectively starting from 04.30 AM, 10:30 AM, 4:30 PM, 10.30 PM (CEST TIime).
Forecast model: Global Forecast System (GFS) with 0.25°x0.25° (lat x lon) spatial resolution.
NOTE: in central European countries, when solar time is in effect, the CET time is used, which is equal to UTC +1 hour, while when daylight saving time is in effect, the CEST time is used, which is equal to UTC +2 hours. Right now it is 7:10 UTC.
See the GFS analysis maps archive from 2013 to today
To see the GFS ANALYSIS MAP ARCHIVE from 2013 to today click on the link.