Forecast discussion, Sun., Sept. 3, morning
Background ozone levels this morning are lower than yesterday (13
ppb at Galveston today versus 38 ppb yesterday). Winds overnight
remained south-westerly. With the deep layer of stronger westerly
winds this morning, I expect winds to remain westerly throughout the
day. Therefore, the ozone distribution will be similar to that of
yesterday. Areas east of Houston will see the highest ozone amounts.
However, I expect lower peak values than yesterday. The MM5 has a
sea breeze developing in the late afternoon with winds still having
a SW component behind the front. There is a slight chance of late
afternoon showers as we have had cumulus clouds develop north of the
city, moving south over the past few days, and the synopitic weather
pattern has not changed.
Max temperature 100+.
Quick Look at Tomorrow
Winds aloft have been from the northeast and look to gain
strength. By tomorrow afternoon these stronger northeasterly winds
should mix down into the boundary layer so that the surface winds
become more northeasterly. If this happens, there could be high
ozone exceedences as dirty continental area moves south over
Houston. Stations with exceedences would be located south and west
of the ship channel. There is little chance for precipitation
tomorrow as dew points decrease and moisture at mid-levels
Models over the next several days continue with the stronger
northeasterly winds aloft with the synoptic pattern not changing
Forecaster Stephanie Naumann
The outlook is much like yesterday. Morning winds are from the
west in the lowest 1 km at 10-15 kt. Low cloud cover will be spotty
through the morning and early afternoon. Because of the strength of
the winds, the Galveston Bay breeze will be weak or nonexistent.
Winds will remain westerly until early afternoon, when the Gulf
breeze will cause winds to become southerly. Highest ozone will be
east of the Houston ship channel during the afternoon, with the
urban plume then being carried to the northeast during the evening.
An observed ozone exceedence is unlikely; background ozone levels
are very low. Hourly averages of 100 ppb are likely.
Multi-Day Outlook High pressure will remain over the area,
despite the approach of a cold front into Arkansas on Saturday. The
airmass should become dirtier, as large-scale trajectories will
originate from the southeast United States and cross the northern
Gulf according to the Grell model run. The situation should persist
for several days, with precipitation unlikely.