NW FL Weather (11-3-2016) - Some Cooler Weather, but What About Rain?

Here's the latest webcast for Northwest Florida as of 4:45 PM, November 3, 2016. Discussion follows below:

I know that some of you are tired of the heat, and some of you are embracing it. Either way, "What goes up must come down." Temperatures will finally be settling back to being more fall-like. We won't be frigid, but it will be rather cool compared to what we had lately. But, what about our rain situation?

Across Northwest Florida, the last day of measurable rain for most of us was back in late September. In fact, Pensacola has had 37 days (as of Nov. 3) without measurable precipitation. The record for longest streak of no measurable precipitation for Pensacola is 49 days set back in 1952. It's uncertain if that record will hold.

In the webcast, I mentioned some "model uncertainty" as we head into next week. Here's a bit of what I mean.

First, we're going to take a look at the mid to upper levels of the atmosphere (500 mb, or about 17,000 ft.).

This is the GFS model out 168 hours representing what the atmosphere could look like at 7 AM Nov. 10. The shaded colors on the map represent the 500 mb heights and the black lines are the surface pressure (isobars). Generally, the lower the heights, the colder the temperatures are aloft. On this map, there is a cut-off low over the Central Plains. It is cut-off from the main flow which is to the north (where the tighter color gradient is. This gives us a southwesterly flow leading to more moisture flowing in. The increased moisture generally leads to higher rain chances. Also, there is an inverted surface trough seen in the isobar pattern over the lower and mid Mississippi River Valley. This could help produce some lift, which, again, could lead to higher rain chances.

Now, contrast the GFS to the European (ECMWF) model. This is the same map as above, just a different model. Notice, instead of a cut-off low over the Central Plains, there is generally a ridge. There is a weak cut-off low over New Mexico, Arizona, and northern Mexico. There is also a trough off the east coast, which is where the cut-off low essentially originated. The trough, basically, split into two parts, and the connection between the trough and the cut-off low weakened. In theory, this weakens any front that would come through our area. Thus, probably not a good chance of rain from this scenario. Plus, the cut-off low is too far west to give us any good influence from the Gulf of Mexico.

Unfortunately, this disparity between the models leads to very low confidence in longer term, and I do not feel like it would be wise to advertise anything greater than a 30% chance of rain next week.

Now, there are more models out there, but the GFS and the ECMWF are generally the most reliable. Both have their strengths and their weaknesses. Also, this is just one variable of the many that we could look at. The 500 mb heights is, in my opinion, the best to look at for the overall pattern. However, it is important to focus on not just one run, but the trend that the models show.  The models have consistently shown a change in the overall pattern which would allow some cooler air and possibly higher rain chances than what we've had. The GFS, in this case, is on the stronger side, and the ECMWF is on the weaker side. There is still plenty of time to watch this system over the several days to see how it evolves. I will keep you updated through these blogs and through webcasts.