Monday, July 30, 2012

Active Fall Pattern Emerging

An active pattern looks to be in store this fall if the CFS is to verify.

The 500mb forecast for October shows a depression of height lines on the West Coast which has been outlined in blue. This depression is characteristic of a storm track pushing through the West Coast and through the Southwest. This track is traditional for what can become severe weather outbreaks in the Southern Plains. The area outlined in red is for where this pattern could produce an active weather pattern going into fall.
This pattern could be temporary, as the CFS does not predict this depression on the West Coast going into the rest of fall and early winter months. However, I find this to be an interesting development, as this would essentially break down the ridge that has been spreading record-breaking heat across much of the nation.


Organized Severe Weather Potential in Midwest in Early August

There is a severe weather threat over the Upper Midwest and Midwest into the western Great Lakes in early August, particularly on Saturday, August 4.

A disturbance is forecast to press through the US/Canada border around Minnesota on August 4. As the disturbance enters the region, mid and lower level winds are forecast to increase in response to friction between the disturbance and a mega-ridge in the Southern US.
As the system deepens over the Upper Midwest, 850mb winds are progged to increase over the northern Plains into the Lower Great Lakes as the atmosphere encourages organized severe weather to form. The presence of instability worthy of organized severe weather looks to be significant, with instability values on the order of over 5500 j/kg in the Lower Great Lakes region, with roughly 2000-4000 j/kg in the Upper Midwest, where 850mb winds may be stronger than those to the south, thus encouraging more organized severe weather potential.
I find it likely that an organized severe weather threat will pan out in the afternoon and evening of August 4, with the Upper Midwest likely containing organized severe weather, and the Midwest dealing with a more volatile atmosphere but with less lower level winds that would specialize in severe weather. Despite the lack of favorable winds, there remains an amount of winds that I find it possible for an organized severe weather threat to develop in the Lower Great Lakes as well.


Invest 99 Forms; Development in Caribbean Possible

Invest 99 has formed off of Africa with little evidence of circulation but an abundance of showers and storms.

Satellite imagery indicates that Invest 99 is composed of several clusters of showers and thunderstorms, with what could be a weak center of circulation in the middle of the image shown above. However, no significant circulation is evident, nor any enhanced convection around the weak circulation. Thus, the invest appears weak at this time.

However, the GFS Ensembles (GEFS) are forecasting this invest to trend westward and into the Caribbean, shown as the circles in the above image. This image shows 1008 and 1048 isobar markings, meaning that this invest could stay in fairly weak territory. Despite this, I find that the Caribbean may be supportive enough for development should the MJO race around to Phases 8-2 in the next 5 or 7 days in order to make a 'perfect storm' of development potential. Whether that happens remains to be seen.