The storm is passing over waters of 29 °C — approximately 0.5 °C above average in temperature — and is an unusually wet storm, with amounts of water vapor near the very high end of what is observed in tropical cyclones (
precipitable water values up to 3.0 inches.)
Moreover, the amount of water in the atmosphere, also known as
the precipitable water value, or PWAT, will be 1.50 to 1.75 inches.
Not exact matches
By several meteorological measures, the airmass associated with this storm is pretty extraordinary: the amount of atmospheric
water vapor (
precipitable water) expected to be present near San Francisco on Saturday morning may be close to the all - time record
value for any time of year.
As expected, amounts of
precipitable water are greatest over warm, equatorial regions and decrease more or less continuously with increasing latitude down to very low
values over the cold, polar regions.