QFF is a Q code

Q code

The Q code is a standardized collection of three-letter message encodings, also known as a brevity code, all of which start with the letter "Q", initially developed for commercial radiotelegraph communication, and later adopted by other radio services, especially amateur radio...

. It is the MSL pressure derived from the barometric pressure at the station location by calculating the weight of an imaginary air column, extending from the location to sea level, assuming the temperature

Temperature

Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...

 and relative humidity

Relative humidity

Relative humidity is a term used to describe the amount of water vapor in a mixture of air and water vapor. It is defined as the partial pressure of water vapor in the air-water mixture, given as a percentage of the saturated vapor pressure under those conditions...

 at the location are the long term monthly mean, the temperature lapse rate

Lapse rate

The lapse rate is defined as the rate of decrease with height for an atmospheric variable. The variable involved is temperature unless specified otherwise. The terminology arises from the word lapse in the sense of a decrease or decline; thus, the lapse rate is the rate of decrease with height and...

 is according to ISA

International Standard Atmosphere

The International Standard Atmosphere is an atmospheric model of how the pressure, temperature, density, and viscosity of the Earth's atmosphere change over a wide range of altitudes. It has been established to provide a common reference for temperature and pressure and consists of tables of...

 and the relative humidity lapse rate is zero. QFF also stands for Quo Fata Ferunt (a Dutch conspiracy website).

QFF is the location value plotted on surface synoptic chart and is closer to reality than QNH

QNH

QNH is one of the many Q codes. It is defined as, "barometric pressure adjusted to sea level." It is a pressure setting used by pilots, air traffic control , and low frequency weather beacons to refer to the barometric setting which, when set on an aircraft's altimeter, will cause the altimeter to...

, though it is only indirectly used in aviation.

This is the Australian Bureau of Meteorology method; QFF calculations differ among meteorological organisations. Another definition of QFF assuming an isothermal layer at the station temperature can be found in the article Mean sea level pressure.

This is the barometric pressure at the surface reduced to MSL using the observed temperature at the surface (this assumes an isothermal layer from MSL to that surface). QFF accounts from the effect that temperature has on the pressure lapse rate and therefore the resultant calculated pressure. The range of QFF so far recorded, low pressure to high pressure of, is from 856 to 1083 hPa.