New formulas will be added providing you submit any formulas you know of that are not listed here.

The Wind Index (WINDEX) is defined as a parameter, developed by McCann (1994), that indicates the maximum possible convective wind gusts that could occur in thunderstorms. The WINDEX is represented by the following equation:

WI = 5[HM*RQ(G^2 - 30 + QL - 2QM)]^0.5

where HM is the height of the melting level in km above the ground; G is the temperature lapse rate in degrees C km-1 from the surface to the melting level; QL is the mixing ratio in the lowest 1 km above the surface; QM is the mixing ratio at the melting level; and RQ = QL/12 but not > 1

MB = Surface Level Pressure
	Do until MB <= 500
		Q = (WBc + 273.15) * ( 1000 / Mb ) ^ 0.286 + (3 * M)
		If Q > Qsw then
			Qsw = Q
		End If
	MB = MB - 25
	Loop

SFC100 = Surface Level Pressure - 100
MB = Surface Level Pressure
	Do until MB <= SFC100
		Q = (WBc + 273.15) * ( 1000 / Mb ) ^ 0.286 + (3 * M)
		If Q > Qwmax then
			Qwmax = Q
		End If
	MB = MB - 25
	Loop

LSI = Qsw - Qwmax

SWEAT = 
12 [Td(850 mb)] + 20 (TT - 49) + 2 (850mb wind speed) + 500mb wind speed + 125 (sin(500mb wind dir - 850mb wind dir) + 0.2)

where D = Td850 (°C); if D < 0, change it to D = 0 
	TT = total totals index; if TT < 49 then drop term 
		v8 = 850 mb wind speed (kts) 
		v5 = 500 mb wind speed (kts) 
		
		S = sin [wind direction at 500 mb (degrees) - wind direction at 850 mb] 
		the term 125(S + 0.2) should be dropped in any of the following cases: 

			when the wind direction at 850 mb is between 130° and 250° 
			when the wind direction at 500 mb is between 210° and 310° 
			when (wind direction at 500 mb - wind direction at 850 mb) > 0 
			when v8 < 15 kts and v5 < 15 kts 

SWEAT is only used to predict severe thunderstorms. Values over 300 are considered
a severe producing atmosphere.


Meaux Saturation Pressure Curve Formula
dryr = (dry bulb temperature deg.F) + 459.67  <--conversion to Rankine
Psat = 29.9213 / (EXP((671.67 - dryr) * 35.913 * (dryr ^ -1.152437)))
Note on this formula from the author:
14 years ago I purchased a SF901 computer automotive engine dynometer.
The dyno came with a psychrometric lookup chart to lookup vapor pressure.
Part of engine dyno testing , is the "ability" to have repeatable "standardized"
testing...this means that along with trying to control / isolate every componet
variable...weather influences / conditions have to accounted for!

(Note=> the racing industry uses 60 deg F instead of 59 degF as part of
STP ) The raw, uncorrected Horsepower and Torque output is corrected
(standardized) to 29.92 inches Hg. / 60 deg. F / 0.00 % Relative Humidity
through a "correction factor" in part computed by = Barometric press. Hg - Vapor press Hg.
The more accurate the weather data ..the more accurate / repeatable testing.

The included dyno vapor pressure chart was hard to read and hard to
determine vapor pressure accuracy to better than a 1/10th inch Hg.,
so I began research 14 years ago at local college libraries on various
weather formulas ..... I came across Smithsonian Meteorological Tables from -60 F to
+212F with saturation data to .00001 accuracy, just what I was looking for,
but the formulas listed in Smithsonian Tables did not always match their
data especially being able to use only 1 formula to cover -60F to +212F range,
so I researched through all the saturation - vapor pressure formulas I could
find ......couldn't find one single formula that would "mirror" the
Smithsonian data,..so I began to develop my own formula....in 1995 I
finally finished my formula that does "mirror" Smithsonian data from -60F to
212 F with as much accuracy as their published data!

(c)1995 by Larry Meaux/MaxRace Software, All Rights Reserved.
Larry Meaux ( MaxRace Software & Meaux Racing Heads/Engines)
9827 LA Hwy. 343
Abbeville, LA 70510
337-893-1541
This formula "mirrors" Smithsonian Meteorlogical Tables from -65 F to 212 F deg



Wet Bulb Temperature

Here is a process requiring only Tc, RH and P (mb) as input:
	** Note that if you want to estimate Wet Bulb and not have to enter Pressure, replace all 'P' variables
	** with a realistic average pressure for the level you are calculating. Example: Surface might be best
	** represented with an average P of about 985. Error should be no more than 0.2° by using this constant.

Variables:
Tc = Temperature in Degrees C
RH = Relative Humidity in form 88 not 0.88

Optional Variable (for more accuracy):
P = Pressure
	or
Constant (with up to 0.2° inaccuracy):
P = 985


Tdc = ((Tc - (14.55 + 0.114 * Tc) * (1 - (0.01 * RH)) - ((2.5 + 0.007 * Tc) * 
(1 - (0.01 * RH))) ^ 3 - (15.9 + 0.117 * Tc) * (1 - (0.01 * RH)) ^ 14))

E = (6.11 * 10 ^ (7.5 * Tdc / (237.7 + Tdc)))

WBc = (((0.00066 * P) * Tc) + ((4098 * E) / ((Tdc + 237.7) ^ 2) * Tdc)) / ((0.00066 * P) + (4098 * E) / ((Tdc + 237.7) ^ 2))

For questions or comments about these formulas, or if you would like a formula that you don't see listed here, email us: Convective Development