Thunderstorms Mon. evening in Tennessee into Georgia helped develop what's termed a "mesoscale vorticity maximum" -- or, more simply, a weak upper level disturbance. The disturbance moved into Southeast Ga. during peak heating Tue. triggering numerous thunderstorms that moved south & east. The sea breeze & many outflow boundaries also helped focus the storms. And this may just be round #1 in what could be a pretty active night of storms which is atypical for this time of year as we usually see our late day storms die out in the evening. But a pretty strong upper level disturbance is diving southeast into Alabama & Georgia & has ignited clusters of storms. It's possible that some of these storms will continue overnight across the First Coast despite earlier storms & diurnal cooling. Yet another disturbance will move into the area Wed. afternoon & should again help afternoon thunderstorms to erupt across the area. Intensity & coverage could be limited some, however, by cloud cover.
"Dolly" will be rolling into far South Texas & far Northern Mexico Wed. Go to our "Hurricane Center" & "Talking the Tropics With Mike" for specific info. Some
interesting sites to look at as "Dolly" comes ashore: webcams from Padre Island & Brownsville.... "Hurricane Hollow" ....& W. Gulf & coastal Texas buoys.
Speaking of the tropics....the Madden-Julian Oscillation has "done its thing". Velocity
Potential Anomalies (green indicates upper level divergence which aids convection, brown is the opposite) have maxed out over the E. Pacific & most of the Atlantic Basin. Large areas of upper level divergence often times correlate to areas susceptible to tropical development. The last large area of "upward motion" helped several tropical cyclones in the E. Pacific as well as "Bertha", "Cristobal" & "Dolly" in the Atlantic Basin. The tail end of this upward motion is now in the E. Atlantic & is probably helping the strong wave near the Cape Verde Islands. So we will now go into a period of "sinking motion" -- large scale subsidence (where air rises in one area, it has to go down in another) behind the large area of upper level divergence which should result in less tropical activity. THAT DOES NOT MEAN NO TROPICAL CYCLONES!....but at least fewer & less frequent. Timing the movement of upward & downward motion is not easy but is generally roughly about every 3-6 weeks or so & can be an especially good indicator of tropical activity when the ENSO is near neutral such as it is now (trending out of the strong La Nina). Our next period of upward motion would appear to be somewhere in mid August, maybe a little later OR SO. This would correspond with the climatological high end of the hurricane season, so it would be no surprise if mid Aug. to early or mid Sept. would be "tropically busy".
