Re: Tulsa forecast - High of 100, Low 75 - All 4 days

On Aug 9, 1:02 am, Speeders & Drunk Drivers are MURDERERS
<xeton2...@xxxxxxxxx> wrote:
You gotta be crazy to actually attend the event when you can watch it at
home.

PS - anyone who says the afternoon humidity will be 100% is forever
banned from RSG. As i've explained countless times before, that never
happens. At a temp of 100 the RH will be under 45%.

I recently asked noted weather expert, Joseph Bartlo, about humidity
and he volunteered this nice explanation:
===============================

100% humidity means the air is saturated, which does as you say
implies some of the vapor in the air becomes liquid and the dewpoint
equals the temperature. If the temperature continues decreasing, more
water vapor becomes liquid - more dew forms and fog. Only if that
persists awhile does the fog become thick. Because nocturnal cooling
occurs from the ground up, most nights you don't see much fog in the
air but dew over the ground which was cooler.

Thus when the temperature increases during day, relative humidity
decreases - that being the water vapor pressure divided by that which
exists at saturation. The higher the temperature, the higher the
dewpoint must be to saturate air, so lower *relative* humidity.
Example: at 8 AM in Chattanooga this morning, the temperature was 74°
& dewpoint 71° with a relative humidity of 90%. By 1 PM, the
temperature was 88° and the dewpoint still 71° with a relative
humidity of 57%. Then there was a thunderstorm.

Dewpoints above 80° are rare - typically in your area at this most
humid (*absolute* amount, not necessarily relative) time of year it is
in the low 70's today. So use this calculator:

http://www.srh.noaa.gov/elp/wxcalc/dewpoint.shtml

and see how the relative humidity changes as temperature rises into
the 90's (station pressure was around 993 mb today - exact value
unimportant). The heat index:

http://www.srh.noaa.gov/elp/wxcalc/heatindex.shtml

certainly was higher than the temperature (94° ), but because
saturation requires about twice as much water vapor for every 10°C (18
°F), relative humidity is never close to 100% at those temperatures -
about th highest it'll be with a temperature of 95° is 65%.

A bit wordy perhaps, but I like to explain things well if the person
wants to read.

.

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