Dave Murray’s Fall 2012 Long-Term Forecast
Summer has been a wild ride with monster temperatures and a heat wave that started early and stuck around for a long time. But for a lot of that heat wave, we were dealing with intense dry heat and drought. Dry heat is almost unheard of for long periods of time in St. Louis. But it’s time to move ahead. September is a month that can have a split personality, especially when it comes to temperature. I have seen many September’s that have been delightful, day and night, but also others that have been a beast and yet others when rather cold air settles in rather quickly. Like the summer, this fall promises to be a struggle for long range forecasters. One of the key features is the building “el Niño”, but it looks weak and will start to fade in early winter. Let’s get to work.
A weak El Niño will set in during the fall. We are seeing mixed signals from the atmosphere, just what I need after this summer. But I think the main feature in September will be the effect of the hot summer and the pounding drought, aka the heat and dry conditions will be tough to knock out. Temperatures will stay very warm to, at times, hot in the month of September. It will be a nod to the summer's of the 30's, 50's, mid 60's, and early 80's. Those hot summers also brought some intense September heat. Now, it will not be the pounding heat of midsummer. It is the early fall version. Look for temperatures to be well above average and I would not be surprised if we see a few more records fall, especially in the first half of the month. The A.C. and fans will still be hard at work. Now, we will see some pull backs at times, especially the second half of the month, but there will be some intense heat for high school and college football games. But again, let’s hope for little correction in the heat after the middle of the month, but it looks small.
We move on to rainfall. You already know where I’m going with this: droughts tend to be slow in developing and slow in reversing. Don't fight the tape. September typically is a very dry month for St. Louis. Not a good sign for for moisture patterns in September. There will be some attempts at rain and even a few storms during the month, but fronts that drop down in the occasional northwest flow will be greeted with little moisture from the Gulf of Mexico and our bone dry soil and vegetation. The exception would be if we got a western Gulf of Mexico hurricane that would try to pump moisture our way. That is just a maybe this September as the tropics shut down. When in doubt, lean warm and dry this September.
Things to look for in September:
- Black and white garden spiders are common around the home
- Look for puffballs and other fall mushrooms
- Listen for migrating birds in the evening hours
September 2012 Highlights
- Temperatures look warm to hot especially first half of the month. Some record highs possible.
- Temperatures will start to cool off slightly the last half of the month
- Rain will be limited and the drought goes on
On to the middle month of the fall season, the month of October. It is a month were the hard core edge of summer shuts down, but the swings of winter still not ready to take place. It is also a month known for its mild days and cool to at times chilly nights. The fall colors usually kick into gear but after this summer with the heat and drought those colors could be a real struggle, despite a wet spring. Look for lots of brown leaves this season. October is also a month that we lose a lot of daylight and the days quickly get shorter and shorter.
It looks like a split flow will develop in the jet stream early October, a pattern rather typical of el Niño. The southern track becomes very active and the northern jet is rather weak. That pattern should now hold through fall and into winter. This is a pattern that should start the correction from the intense summer heat and drought. However, the correction will be slow. I do feel we will start to see a slow cool down in temperatures as we go through the month, but it will be a struggle for the first 20 days. Because of that, the month of October will bring above average temperatures once again. Look for a cool down, day and night, the last 10 days of the month but no deep cold in sight. More treats than tricks for Halloween.
The temperature pattern is close to the analogs of the 1950's and as a result the moisture pattern will also be similar. That means more dry time. The drought goes on and no late season tropical action to help out. October is typically another dry month on average and this will stay true to form. That’s more bad news for the farms and gardens. Even the swing to a bump up in rain will be tough to come by the end of month. Rainfall will be below to well below average.
This to look for in the month of October:
- Persimmons start to ripen
- Look for spiders ballooning on gossamers on clear, windy days
- The juncos arrive from Canada
October 2012 Highlights
- Temperatures will stay above average for the bulk of the month
- A slight cool down for the end of the month but no cold air expected
- The drought goes on with little hope in sight for drought-busting rains
Time to wrap up the last month of the fall forecast, November. It is a month when we watch the last of the leaves drop with a chill in the air. Temps consistently get colder at night. Before you know it, we will be talking about snow, Thanksgiving will be upon us, and high school football will be coming to an end.
November always brings a cool down no matter what the weather pattern. However, the drought that has been locked in since late June will continue to have a monster effect on our weather. Drought keeps drought going and it is tough to break. The drought’s effect on temperature will stay in control. There will still be plenty of warm air, but just like drought makes heat stronger it also will make the cooling effect stronger. So I’m looking for November to turn colder, especially after the first week of the month. The cold air will really dig in around Thanksgiving time once central Canada opens up. The drought will provide the highway for the cooler to colder air to stream our way. There will be some wonderful fall days this November, but get set for colder air to come on rather quickly.
As for moisture, the split flow in the jet stream that develops in October will get stronger in the month of November. The southern jet will be king but will be too far south with the heaver rains from Texas along the Gulf and over the southeast. This track will try to flex two to three rounds of wet weather our way in November. Each flex could also fire some intense November thunderstorms, the famous second season. We will take any rain we can get but I still think rainfall will be a little below average for the month. Did I mention, drought is very slow to change.
Things to looks for in November:
- Birds begin gathering at the feeders
- Scan the leafless trees for paper nest of the bald-faced hornets
- Woodchucks are asleep in underground nests
November 2012 Highlights
- Mild to start then a strong cool down takes hold and temps end up average to a little below average
- The drought remains the dominant feature
- Looking for 2 to 3 rain events that should include thunderstorms
Fall 2012 Summary
So let’s sum-up this next season. El Nino peaks and starts to fade away as we get into winter. Patterns in the Pacific in time will go neutral but the large scale global patterns we look at for hints in the long range will get masked by the intense drought for about 60 percent of the nation. The drought keeps temperatures warmer than they should be for much of the fall, at least until November settles in. The drought will tend to deflect major storms to our north, west, and south. However the fading el Niño in the fall season has my interest for the winter season. Winter may come on the moisture patterns could really start to correct. Winter 2012-2013 could be very interesting with the split flow in the jet stream and battles between wet storms and cold air. But that’s for my next long range forecast.