Wind chill (*** Attention Met Office Press Team ***)

61 views

xmetman

Jun 21, 2018, 4:29:17 AM6/21/18
to Weather and Climate

There's a terrific contrast in wind chill across northwest Europe this morning

Jack Harrison

Jun 21, 2018, 4:07:41 PM6/21/18
to Weather and Climate

Bruce.

Do you use the formula when calculating wind chill?

or this one?

The first would seem to be the more intuitive:-)

Jack

xmetman

Jun 22, 2018, 3:56:52 AM6/22/18
to Weather and Climate
Yes I use the first one. There are a couple of others but the JAG is the best one around I reckon.

function CalcJAG(td: double; ws: integer; Units: TWSUnits): double;
var
kph : double;
begin
// The standard Wind Chill formula for Environment Canada is:
// WC = 13.12 + 0.6215T-11.37V^0.16+0.3965TV^0.16
// where:
//       WC = wind chill index
//        T = air temperature in Celsius
//        V = wind speed at 10 metres in km/h
// WCTI=(13.12 + (0.6215*T))-(11.37*(V^0.16) + ((0.3965*T)*(V^0.16))

if (td<>missing) and (ws<>missing) then
begin
if Units=wuMPS then
kph:=MpsToKph*ws
else
kph:=KtsToKph*ws;

result:=13.12+(0.6215*td)-(11.37*power(kph,0.16))+(0.3965*td*power(kph,0.16));
end
else result:=missing;
end;
//------------------------------------------------------------------------------------------------------------------------------
function CalcSiple(td,ws: double; Units: TWSUnits): double;
var
mps : double;
begin
if (td<>missing) and (ws<>missing) then
begin
if Units=wuMPS then
mps:=ws
else
mps:=KtsToMps*ws;

if ((mps>1.79) and (td<33)) then
result:=33+(td-33)*(0.474+(0.454*sqrt(mps))-(0.0454*mps))
else
result:=td;
end
else result:=missing;
end;
//------------------------------------------------------------------------------------------------------------------------------
function CalcCourt(td: double; ws: integer; Units: TWSUnits): double;
var
mps : double;
begin
if (td<>missing) and (ws<>missing) then
begin
if Units=wuMPS then
mps:=ws
else
mps:=KtsToMps*ws;

if ((mps>1.79) and (td<33)) then
result:=33+(td-33)*(0.550+(0.4178*sqrt(mps))-(0.0454*mps))
else
result:=td;
end
else result:=missing;
end;
//------------------------------------------------------------------------------------------------------------------------------