|Forecast discussion, Thu., Aug. 24,
Because extensive operations are not planned for today, the
forecast will focus on the longer-range outlook.
Winds at the surface are generally light from the northeast, a
morning wind direction we haven't seen yet and which favors the
early morning plume from the Ship Channel drifting slowly southwest
and then drifting slowly north again over the city as the light
southerly winds aloft mix down. Unusually rapid ozone increases
during the morning are possible near the center of the city
depending on the distribution of thunderstorms.
Speaking of which, the thunderstorms over the Gulf are as
widespread as they were yesterday, but not as numerous. There are
light showers about; deeper convection should develop with the
bay/gulf breeze convergence late this morning and spread inland
across the city during the early afternoon. Chances of showers
cleaning up the air this afternoon are 80%.
Max temperature lower 90s, higher well inland away from the
convection and gulf breeze.
Quick Look at Tomorrow
General drying trend is continued by all models. Tomorrow
scattered showers along the bay/gulf breeze are likely, but light
large-scale winds and a better chance of a land breeze imply high
ozone potential in between the showers. Showers are also likely
tomorrow over the piney woods, but the inland penetration of showers
probably won't be as great tomorrow as today or yesterday.
The met and chem models agree that boundary layer trajectories
will originate from the southern Mississippi River valley starting
on Saturday. This implies much less convection, particularly on
Sunday and beyond. As high pressure continues to build over us, the
Aviation model forecasts light northwesterlies at night and
southeasterlies during the day a high ozone flow reversal scenario.
If Debby reintensifies over the eastern Gulf of Mexico, the
associated circulation and subsidence would suppress convection and
bring air from the Midwest and East Coast. Debby is unlikely to hit
us; if it makes landfall in the western Gulf the earliest plausible
day would be Tuesday.
Forecaster John Nielsen-Gammon