METEOROLOGICAL FORMULAS

List of Meteorological Formulas

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

1° Latitude=	69.125 miles
Temp(F)=	Tf= (1.8*Tc)+32
Temp(C)=	Tc= (Tf-32)/1.8
Kelvin(Tk)=	Tk= 273.15 + Tc
Temp (Reamur) =	(25/36)(°F-32)
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-(0.01RH) K= Tc-(14.55+0.114Tc)X-((2.5+0.007Tc)X)^3- (15.9+0.117Tc)X^14 Tdf= (K1.8)+32
Dew Point(F) Knowing Tf=	Tdf= ((((Tf-32)/1.8)-(14.55+0.114((Tf-32)/1.8)) (1-(0.01RH))-((2.5+0.007((Tf-32)/1.8))(1-(0.01RH))) ^3-(15.9+0.117((Tf-32)/1.8))(1-(0.01RH))^14)1.8)+32
Before Winter 2001/2002 Wind Chill(F)=	Wc= 0.0817(3.71SQRT(WIND SPEED MPH)+ 5.81-0.25WIND SPEED MPH)(Tf-91.4)+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))

Wind Speed & Direction Estimation Calculation

Summer Simmer Index(SSI)=	SSI= 1.98(Tf - (0.55 - 0.0055(RH))(Tf-58)) - 56.83
Saturation Vapor Pressure(Mb)=	Es= (6.1110^(7.5Tc/(237.7+Tc))
Vapor Pressure(Mb)= From Dew Point	E= (6.1110^(7.5Tdc/(237.7+Tdc)))
Vapor Pressure(Mb)= From Temp and Humidity	E = (6.1110^(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= (0.622E)/(Mb-(0.378E))
Relative Humidity(%)=	RH= (E/Es)*100
Relative Humidity(%) Knowing Tdf and Tf=	RH = (((6.1110^(7.5((Tdf-32)/1.8)/(237.7+((Tdf-32)/1.8))))/((6.1110^(7.5((Tf-32)/1.8)/ (237.7+((Tf-32)/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 Ew = 6.1078 * exp([(9.5939 * Tw) - 307.004]/[(0.556 * Tw) + 219.522]) 'Saturation Vapor Pressure Dry Es = 6.1078 * exp([(9.5939 * Td) - 307.004]/[(0.556 * Td) + 219.522]) E = Ew - 0.35 * (Td - Tw) 'Actual Vapor Pressure Relative Humidity RH = (E / Es) * 100 Dew Point Tp = -1 * {[ln(E/6.1078) * 219.522] + 307.004} / {[ln(E/6.1078) * 0.556] - 9.59539}
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(Tf-Tdf)
Rankine Temperature(R)=	R= Tf+460
Saturation Mixing Ratio(g/kg)=	Ms= 3.88426610^[(7.5Tc)/(237.7+Tc)] OR MORE ACCURATELY 0.622 * Es/(P - Es)
Mixing Ratio(g/kg)=	M= RHMs/100 & M= ((0.622E)/(Mb-E))*1000
Virtual Temperature(C)=	Tv= [(1+1.609M)/(1+M)]Tc
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(sfc-500 mb)
K Index=	KI= Tc(850mb) - Tc(500mb) + Tdc(850mb) - 2* Tdc(750mb) - Tc(750mb) Basically double the KI value to calculate the chance of thunderstorms.
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) * (0-1 km Helicity / 100) * (0-6 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((30.551.0033(MVVMVV))/(89.8900))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
TQ Index (low top convection potential)=	(T850 + Td850 ) - 1.7 (T700) > 12 Storms Possible > 17 Low-Top Storms Possible
Delta Theta-E= (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 If U < 0 And V < 0 Then ANG = 0 If U > 0 And V < 0 Then ANG = 360 Direction = (180 / PI) * Atn(U / V) + ANG
BRN Shear =	0.5 (( 6km AVG U Component) ^ 2)
Bulk Richardson Number =	BRN= (CAPE / BRN Shear)