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Activity Increasing

In the matter of 48 hours, the tropics have become truly active for the first time all season. There are 3 areas of interest at the moment. Of most pressing concern is a possible subtropical development off the coast of North Carolina. NHC has called this disturbance Invest 90L. Shear is fairly high over the disturbance right now (Figure 1), but since any intensification will most likely be of the subtropical variety, high shear is not as crippling. The QuikSCAT satellite pass from this morning is quite interesting (Figure 2). Invest 90L has a strong circulation and fast winds to its south. It wouldn't surprise me to see NHC task a reconnaissance mission into 90L.

Figure 1. Shear analysis from UW-CIMSS. There is strong shear over Invest 90L and moderate shear over Invest 99L.
Figure 2. QuikSCAT image from 7AM EDT for Invest 90L. Note the closed circulation and fast winds to the south.

Another area of interest is the same tropical wave we've been talking about over the weekend. Invest 99L does not have a closed circulation yet and convection has been limited. However, there is still a moderate chance this could develop. Shear is not high enough to completely inhibit convection (Figure 1) and there are some strong surface winds to the north (Figure 3). NHC is ready to issue a reconnaissance flight into 99L if the convection re-fires.

Figure 3. QuikSCAT image from 5AM EDT for Invest 99L. The red "L" indicates the center of low pressure. There is no closed circulation, but winds to the north are close to 35 mph.

The last feature of concern is the tropical wave located just south of the Cape Verde Islands. While NHC has not issued an Invest for this wave yet, all of the global models are forecasting development. As with the Invest 99L, there is dry air to the north of the system (Figure 4), which may suppress thunderstorm activity. This system is still a long way from any land, so we have plenty of time to monitor it.

Figure 4. Saharan air layer analysis from UW-CIMSS. The yellows and reds indicate dry, dusty air.

Posted by Adam Moyer | Permalink