(KTVI)-Like last Fall, we will be dealing with a weak el Niño and that means mixed signals in the atmosphere. Those mixed patterns will result in some rather impressive swings in temperature and moisture.
For temperatures, the first 15 to 20 days of the month will be on the mild to warmside. During this stretch temperatures will be above average, both day and night. Records are tough to come bybut the trend is for a little more of a late Summer than a Fall feel. Some college and high school football games may be a little steamy.
Howeverthat will not hold for the last quarter of the month of September. This is the run where I see one or two rather impressive cold shots coming in from the north/northwest. These arctic type cold fronts would bring a big chill to town and maybe a shot at a late September frost or freeze. That would be a concern for the fall harvest and for the home gardens. But the cool feel should get you in the mood for some apple picking and homemade apple pies. It also means it is time to get the heating system checked out
As for moisture, it’s tough to go against the averages in September. It is a month that is typically dry to very dry in the St. Louis area and I do think this September will hold true to form with rainfall running below average. It won’t be bone dry. The cold snap I’m expecting in the last part of September should bring some pretty good rains to the area and there is always the September wild card: the tropics.
September does look like an active month for tropical weather with the focus along the east coast. But if a storm were to slip through and get into the western Gulf of Mexico that would pump some added rainfall our way. My confidence is low with that concept but not low enough to leave it off the table. But in the scope of the entire month, September will be on the dry side and new plantings and the fall gardens will need some water at times.
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
Major September Points:
- Much of the month...mild to warm until the last quarter when colder temperatures will settle in
- Concerns about a late month frost or freeze
- A dry month but not a bone-dry month. The wettest at the end unless a tropical system comes into play
October is typically a wonderful month in the St. Louis region. It is known for its pleasant and dry weather. Of course, this is St. Louis and there are always extremes with rain and temperatures. This is a month when we can really say goodbye to the Summer weather pattern but the swings of Winter are not ready to take control. It is a great transition month with mild days and cool nights.
Mild temperatures come back into the picture for much of the month of October. So the late September cold snap doesn’t last and is not a sign that Winter is going to set in quickly. There are not a lot of great signs showing up on the maps and charts that this anything more than a rather pleasant Fall month. Looking like nice days and cool nights especially as we work through the entire month. The month looks mild but nothing extreme. Temperatures will average out slightly above average with a run of mild October air.
Good news for watching the leaves change color. October displays should be pretty solid this year with the wet spring and the not so hot summer. Also, notice the amount of daylight we lose in October. The days quickly get shorter and shorter.
As for rainfall, very few Octobers are really wet and I think the dry trend will be the rule of thumb this year. Good news for the harvest season and pumpkin picking as drought type weather will be in play. Dry weather is a little less of a concern this time of year and rather typical. Also, tropical action will not be a factor. The season goes quiet at this point in time.
Now there is a second season of strong to severe thunderstorms in late October and November. It does not last very long but there is a little storm bump in the Fall. We will be on the edge of this active pattern, with the focus to our south, but there should be a few mean thunderstorms around late in the month.
Things to look for in October:
- Persimmons start to ripen
- Look for spiders ballooning on gossamers on clear, windy days
- The juncos arrive from Canada
Major October Points:
- Some temperature swings...but overall pleasant days and cool nights
- Rain will be limited, slightly below average. No tropical action
- Concerns about the thunderstorm second season with a few mean storms late in the month
November is the month that always tells us we are living on borrowed time. Fall shuts down and Winter comes knocking at the door. The last of the fall leaves drop and temperatures day and night get colder. And yes, talk of snow can come into the picture.
Its looks like a split flow will develop for the month which is a pattern typical of a weak el Niño. The southern track becomes very active and the northern jet is rather weak. This will be a little weird for this time of year but leaving us in the middle and walking a line between two very different types of weather. Because of this we will see bouncing temperatures, at times mild for November but other times rather cold.
So get ready for a roller coaster ride of temperature readings with some spectacular Fall days and some surges that will quickly remind us we are headed nto the winter season. Have the sweaters and sweatshirts close at hand
On to moisture and the early start of the second season of thunderstorms will take us into the first eight days of the month. Like the end of October, there is some concern of a few mean Autumn thunderstorms. Then the moisture patterns will settle down getting back to a typical rainy weather pattern. Rainfall will end up a little bit above average for the month of November.
Now we also think about some snow starting to fly this month and we may have to do a little more than just think about it. The swings on the split flow will punch in some pretty impressive cold shots and, though moisture will be limited with these pushes from the Arctic, there may be enough to squeeze out a little snow and snow flurries over the last 10 days of the month.
Things to look for in November:
- Birds begin gathering at the feeders
- Scan the leafless trees for paper nests of the bald-faced hornets
- Woodchucks are asleep in underground nests
Major November Points:
- More temperature swings with some mild days but also some impressive cold shots
- Rainfall will be a little above average as moisture patterns increase
- Some thunderstorm concerns early month and snow and snow flurries possible the end of the month
Fall 2013 Summary
Summing up the season, El Niño is in play but it is not a huge factor. It even fades a little as we go through the three months of Fall. There will be some temperature and moisture swings giving this Fall a little more of an average look. My concerns are for an early season cold snap at the end of September and an early start to the season for severe thunderstorms in late October. But like last year, the weak and fading El Niño really has my interest for the upcoming Winter season. The split flow gets going in November and sets up more atmospheric battles that a flow like that will bring. Plus, I like my overall idea that the winters are getting colder. There are some clues but it’s all in the details and that is for my next long range forecast.