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

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xmetman

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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

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

Bruce.

Do you use the formula when calculating wind chill?

{\displaystyle T_{\mathrm {wc} }=13.12+0.6215T_{\mathrm {a} }-11.37v^{+0.16}+0.3965T_{\mathrm {a} }v^{+0.16}}

or this one?

{\displaystyle \mathrm {AT} =T_{\mathrm {a} }+0.33e-0.70v-4.00}

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


Jack

xmetman

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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;
//------------------------------------------------------------------------------------------------------------------------------

Jack Harrison

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Jun 22, 2018, 4:17:25 AM6/22/18
to Weather and Climate
Thanks Bruce.    Much simpler than my method:
...
...
...
Lick finger and stick it out the window:-)

Jack
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