1° Latitude=  69.125 miles 
Temp(F)=  Tf= (1.8*Tc)+32 
Temp(C)=  Tc= (Tf32)/1.8 
Kelvin(Tk)=  Tk= 273.15 + Tc 
Temp (Reamur) =  (25/36)(°F32) 
Temp (Rankine) =  °F + 459.67 
Knots=  Knots= Wind Speed MPH * 0.868976241091 
MPH=  MPH= Knots * 1.15077944802 
Miles=  MI= Kilometers * 0.6214 
Kilometers=  KM= Miles * 1.61 
Kilometers=  KM= Meters / 1000 
Meters=  Meters= Kilometers * 1000 
Meters=  M= Feet * 0.305 
Meters Per Second=  M/S= Knots * 0.5148 
Feet=  Ft= Meters*3.2808 
Inches=  IN= CM / 2.54 
Centimeters=  CM = IN * 2.54 
Pascals(Pa)=  Pa= (Mb*100) 
Kilopascal (Kp)=  Kp= InHg * 3.38638815789 
Millibars(Mb)(Hectopascal)=  Mb= (In*33.86388158) 
Inches of Mercury(InHg)=  InHg= (Mb/33.86388158) 
Dew Point(F) Knowing Tc=  X= 1(0.01*RH) K= Tc(14.55+0.114*Tc)*X((2.5+0.007*Tc)*X)^3 (15.9+0.117*Tc)*X^14 Tdf= (K*1.8)+32 
Dew Point(F) Knowing Tf=  Tdf= ((((Tf32)/1.8)(14.55+0.114*((Tf32)/1.8))* (1(0.01*RH))((2.5+0.007*((Tf32)/1.8))*(1(0.01*RH))) ^3(15.9+0.117*((Tf32)/1.8))*(1(0.01*RH))^14)*1.8)+32 
Before Winter 2001/2002 Wind Chill(F)=  Wc= 0.0817*(3.71*SQRT(WIND SPEED MPH)+ 5.810.25*WIND SPEED MPH)*(Tf91.4)+91.4 
Starting Winter 2001/2002 Wind Chill °F = T = Air Temperature °F V = Wind Speed MPH  35.74 + 0.6215 * T  35.75(V ^ 0.16) + 0.4275 * T (V ^ 0.16)

Heat Index(HI)=  HI= 42.379 + 2.04901523(Tf) + 10.14333127 (RH)  0.22475541(Tf)(RH)  6.83783x10^(3)*(Tf^(2))  5.481717x10**(2)*(RH^(2)) + 1.22874x10^(3)* (Tf^(2))*(RH) + 8.5282x10^(4)*(Tf)*(RH^(2))  1.99x10^(6)*(Tf^(2))*(RH^(2)) 
Summer Simmer Index(SSI)=  SSI= 1.98(Tf  (0.55  0.0055(RH))(Tf58))  56.83

Saturation Vapor Pressure(Mb)=  Es= (6.11*10^(7.5*Tc/(237.7+Tc))

Vapor Pressure(Mb)= From Dew Point  E= (6.11*10^(7.5*Tdc/(237.7+Tdc)))

Vapor Pressure(Mb)= From Temp and Humidity 
E = (6.11*10^(7.5*((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))/(237.7+((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)))))

Specific Humidity(kg/kg)=  SH= (0.622*E)/(Mb(0.378*E))

Relative Humidity(%)=  RH= (E/Es)*100

Relative Humidity(%) Knowing Tdf and Tf=  RH = (((6.11*10^(7.5*((Tdf32)/1.8)/(237.7+((Tdf32)/1.8))))/((6.11*10^(7.5*((Tf32)/1.8)/ (237.7+((Tf32)/1.8)))))*100)) 
Relative Humidity and Dew Point knowing Wet & Dry Bulb Temps 
Relative Humidity & Dew Point using Wet & Dry Bulb Temps
'Saturation Vapor Pressure Wet E = Ew  0.35 * (Td  Tw) 'Actual Vapor Pressure
Relative Humidity
Dew Point 
Dew Point from just T and RH: 
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)

LCL Height (Estimated FT)=  H= 222(TfTdf)

LCL Height (Estimated Meters)=  H= 67(TfTdf)

LCL Height in Millibars = 
SP = (Surface Millibars) * 1000 ST = (Surface Temperature in ° C) + 273.16 SDP = (Surface Dew Point in ° C) + 273.16
'Find the LCL Level and Parcel Temp at LCL Height 
Rankine Temperature(R)=  R= Tf+460

Saturation Mixing Ratio(g/kg)=  Ms= ((Val(Humidity) / 100) / Val(MixingRatio)) * 100 OR MORE ACCURATELY 0.622 * Es/(P  Es) 
Mixing Ratio(g/kg)=  M= RH*Ms/100 & M= ((0.622*E)/(MbE))*1000 
Virtual Temperature(C)=  Tv= ((TemperatureC + 273.16) / (1  0.378 * (VaporPressure / StationPressure)))  273.16 
Lifted Index=  LI= Tc(500mb)  Tp(500mb)

Showalter Index=  SI= 1) From the 850mb temp, raise a parcel dry
adiabatically to the mixing ratio line
that passes through the Tdc(850mb) 2) From that point, raise the parcel moist adiabatically to 500mb. 3) SI= Tc(500mb)  Tp(500mb) 
Vertical Totals =  VT= T(850mb)  T(500mb)

Cross Totals =  CT= Td(850mb)  T(500mb)

Total Totals=  TT= Tc(850mb) + Tdc(850mb)  2*Tc(500mb)

(30 or greater strong thunderstorms) Deep Convection Index =  DCI= T(850 mb) + Td(850 mb)  LI(sfc500 mb)

K Index=  KI= (T850  T500 ) + Td850  T dd700 
Energy Helicity Index =  EHI= (CAPE * Helicity) / 160000

Significant Tornado Parameter = F2+ damage associated with STP values >1  STP= (mean layer CAPE / 1000) * ((2000  mean layer LCL meters) / 1500) * (01 km Helicity / 100) * (06 km Shear meters per second / 20)

ThetaE (any level) = [Saturated Potential Temperature]  ThetaE = (Tc + 273.15) * ( 1000 / Mb ) ^ 0.286 + (3 * M) OR ThetaE = (273.15 + Tc) * ( 1000 / Mb ) ^ 0.286 + (3 * (RH * (3.884266 * 10 ^ [( 7.5 * Tc ) / ( 237.7 + Tc )] ) /100 )) 
Theta (any level) = [Dry Potential Temperature]  Theta= (T + 273.15) * (1000 / P) ^ 0.2854

WMAX (Maximum Potential Speed of an Updraft) =  WMAX = (( SQRT(2 * CAPE) ) / 2 ) / 0.5148

Vertical Velocities can overcome the cap if:  VV > SQRT(2 * CINH)

Convective Temperature=  CT = CCL Tc *(1000.0/CCL Mb)0.286 * (SFC Mb/1000.0)*0.286

Maximum Hail Size=  Hail = 2*((3*0.55*1.0033*(MVV*MVV))/(8*9.8*900))*100 MVV = Max Vertical Velocities in M/S 
Normalized CAPE=  NCAPE = CAPE / (ELm  LFCm)
<= 0.1 Weak Updrafts 0.1  0.3 Moderate Updrafts >= 0.3 Strong Updrafts 
How to calculate CAPE
 
TQ Index (low top convection potential)=  (T850 + Td850 )  1.7 (T700)
> 12 Storms Possible > 17 LowTop Storms Possible 
Delta ThetaE= (Wet Microburst Potential)  (SFCThetaE  LowestMidLevel ThetaE)
>= 20 Wet Microbursts Likely <= 13 Wet Microbursts Unlikely 
U and V Components of Horizontal Wind= SPD is in Knots DIR is in Degrees  U = (SPD * 0.5148) * Sin(DIR * (PI / 180)) V = (SPD * 0.5148) * Cos(DIR * (PI / 180)) 
Speed (Knots) and Direction (Degrees) from U and V Components= 
Speed = Sqr(U ^ 2 + V ^ 2) / 0.5148
If V > 0 Then ANG = 180 Direction = (180 / PI) * Atn(U / V) + ANG 
BRN Shear =  0.5 (( 6km AVG U Component) ^ 2)

Bulk Richardson Number =  BRN= (CAPE / BRN Shear)

Air Density (km/m3) =  D= (mb*100)/((Tc+273.16)*287)

Absolute Humidity =  Ah= ((6.11*10.0**(7.5*Tdc/(237.7+Tdc)))*100)/((Tc+273.16)*461.5)

Station Pressure =  Ps = Altimeter in Inches * ((288  0.0065 * Elevation in Meters)/288)^5.2561

Altimeter Setting =  As =
(Station Pressure in MB  0.3) * (1 + (((1013.25^0.190284 * 0.0065)/288) *
(Elevation in Meters/(Station Pressure in MB 0.3)^0.190284)))^(1/0.190287)

Sea Level Pressure =  SLP = Station Pressure & RFactor You most likely will have Altimeter Setting information that needs to first be converted to Station Pressure using the equation above. You can get historical temperature and dew point information from here. Click 'History Data' > Enter your location > Click Custom. 
Pressure Altitude (Ft) =  Ap = (1(Station Pressure in MB/1013.25)^0.190284)*145366.45 
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 km1 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  QwmaxA cap of 2 degrees Celsius or greater is a good inhibitor of convection. A strong cap is can hold energy down too much and thus cause thunderstorms not to break. A weak cap can cause development to occur before enough energy builds up for the cells to become severe. A median of a strong cap and a weak cap (a cap strength from 12°C) is generally ideal to allow enough time for energy to build and then break the cap, allowing storms to go severe and possibly tornadic.
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 ktsSWEAT 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 3378931541 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