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.

Andrew

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.

Prognosis
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.

Andrew

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.

Andrew

ECMWF Ensembles' Forecast On Par With Expected Winter Conditions

ECHAMA Precipitation Rate Anomaly

ECHAMF Temperature Forecast Anomaly

The ECMWF Ensemble forecasts for December-January-February (DJF) appears to be the most in line with having a reasonable forecast, over other forecast members of the NMME association. Here's why I chose the ECHAMA and ECHAMF, members of the ECMWF squad.

Ridge over Gulf of Alaska (GOA)
There were some models showing warmer than normal temperatures over Alaska, signifying a high pressure over the area. However, after viewing temperature forecasts on the same members, those members showed above normal precipitation for Alaska, not in line with a high pressure over the Gulf of Alaska. Thus, those members were ruled out.

Ridge over GOA + Cool East US
A ridge over the Gulf of Alaska will lead to cooler than normal conditions over the eastern US. Similarly, a low pressure system over the Gulf of Alaska will bring warmer than normal conditions over the eastern US, as was seen last winter. However, despite a warm Gulf of Alaska, a few members showed a warmer than normal Eastern US, disqualifying their reason into their forecasts.

Wet Conditions over the Eastern US
Due to an incoming El Nino, wetter than normal conditions are expected over the Gulf of Mexico coast as well as the East Coast. One or two members displayed below normal precipitation anomalies over the mentioned areas, practically ignoring the El Nino that will be present come winter-time.

All of that said, I find it probable that if a forecast of the NMME members were to verify, it would be the ECHAMA and ECHAMF forecast maps charted above as described above.

Andrew

ECMWF Digs Strong Disturbance; Accompanying Severe Threat Possible

The ECMWF continues to show the prospect for a potential severe weather event in the first week of August, projecting a deepening disturbance over the western Great Lakes area.

This ECMWF solution seems pretty solid. A strong high pressure ridge remains over much of the southwestern US, and this does not look to go away anytime soon. If anything, expansion eastward seems probable. At the same time, a negative NAO currently in place is likely to persist into August, bringing the likelihood of a disturbance swinging down into the Great Lakes/Northeast regions in accordance with the buckling of the jet stream as is typical in a negative NAO.

If such deepening of a disturbance were to occur, an area of instability would be potent over the Midwest as a cold front attached to the back end of the disturbance would likely swing south and may ignite some strong to severe storms across the Midwest area. However, let's not jump to that conclusion just yet. It remains unknown where any cold front may set up, and if any instability could fuel any thunderstorms. Further analysis of the ECMWF at the same forecast hour reveals lower level winds in place over the Midwest, signaling a favorable thunderstorm atmosphere. However, jet stream winds look to be displaced to the east, which would diminish a tornado threat.

Andrew