Posted by Beau Dodson on September 3, 2010
Update: November 7, 2010: Leaning towards December being below normal in temperatures and then January and February above normal. I still believe this is going to be a roller-coaster winter with plenty of swings in temperatures and an active storm pattern.
Update: November 1, 2010: November will likely bring colder than normal temperatures to our region. This will be the only month of the fall season with below normal temperatures.
UPDATE: October 10, 2010 - reminder. I will once again be using the ice storm rating index scale for the upcoming winter season - you can view that index here (thankfully last year we did not need to use it) - click here
UPDATE: September 29th - will post September verification on the 30th. September turned out to be much above normal in the temperature department. We had our wild card tropical system (Hermine) - otherwise the rest of the area experienced below normal precipitation. Some areas had almost no rain. I will post numbers tomorrow.
As we look ahead to October - normal to below normal temperatures are expected for the first half of the month. We could see several days with much below normal temperatures. The second half of the month could bring warmer temperatures. I am still expecting below normal precipitation for October. Again - the wild card in the mix will be tropical activity.
Previous forecast thoughts below...
This forecast was issued on September 3rd and covers the months of September through November. The forecast is not for specific events but rather an overall general weather pattern that we can expect for the three month period. Obviously there will be swings in the pattern.
Current Forecast: Above normal temperatures for the overall fall season (Sept-Nov). Lot of frontal passages with some below normal temperature days. More above normal than below - is the current outlook. Precipitation will generally be below normal. However - a tropical system will be the wild card in the forecast. One of two tropical storms (remnants) and we will quickly see rainfall totals rise. So, keep that in mind. Overall though I am expecting below normal precipitation.
The winter will likely be volatile and full of dramatic swings. Which is not uncommon for our region.
Keep in mind that it only takes one big snow or ice event for the public to perceive the winter as being "severe, extreme, or bad." Just because we may experience above normal temperatures this winter does not mean we won't see extreme swings. I am not a huge fan of long range outlooks. However, a lot of people do show interest in the subject.
Also - as we look ahead to the winter months - above normal temperatures don't always equate to a mild winter. Keep that in mind when glancing over the forecast and the maps. The maps below indicate that the probabilities favor above normal temperatures for the fall and winter months.
If you don't follow my daily updates and forecasts then you will miss out on any forecast changes and specific event forecasts. You can follow me here on the blog or on Facebook. I update Facebook more often - easy to update and quick to follow.
Well, meteorological fall has arrived and with the season change comes the question - what kind of fall and winter are we going to have this year? I have touched on some of my thoughts, on Facebook and here on the blog, over the last few months. You can read previous thoughts here on the blog by skimming back through the postings.
One has to remember that it is nearly impossible to predict specific events more than a few days to a week in advance. So, anyone who tells you that it is going to snow 3" on Christmas Eve is either making it up or aiming for a lucky guess. Forecasters just don't have the capability to forecast specific events in the long range.
The ice storm is great example of this topic. We (NWS, local media, forecasters) gave anywhere from 7-10 days advance notice that a major ice event was possible in our region. But, it would have been impossible a month in advance to give everyone a forecast that included an ice storm. Mother nature just doesn't work that way and we do not have the skills or computer models to see that far into the future. We can, however, tell you that the pattern favors ice storms, snow events, flooding, and severe weather. But - that is just about as specific as our crystal ball will allow us to forecast. Generalities and patterns.
As I said above, what we can do, though, is determine if a certain pattern is conducive to producing above or below normal weather conditions during a particular season of the year. And even then it is not an exact science. Sometimes the signals point in one direction but mother nature decides to take us somewhere else.
So - I am not going to be forecasting specific events. But, rather - I will be forecasting general trends in the data that is currently available and overall patterns that are likely to occur during the months of September, October, and November. There are several offices that have issued their fall outlooks and for the most part I don't see much disagreement in what direction everyone is heading.
La Nina conditions continue to develop over the Pacific. It is likely that this will have a significant impact on the coming fall and winter months. As a matter of fact this La Nina could rank in the top 5 La Nina's in strength. Still a bit early to determine that - the question also remains as to when this La Nina will peak.
I am already seeing signs of more frequent and deeper low pressure systems on the weather map. These systems will develop in the central plains and move northeast into the Great Lakes. This is not only a sign of fall but also of a La Nina pattern.
For the most part - generalizing - fall (September through November) is forecast to bring above normal temperatures with below normal precipitation. That isn't to say we won't see some nice cold frontal passages - we always do. It simply means that the overall pattern favors above normal temperatures during the three month period and that the cool spells should be short lived or transient.
I also want to remind you that one or two tropical storms or hurricanes moving into the Gulf of Mexico, Texas, or Mexico could dramatically alter the forecast for dry weather. If this were to happen then our rainfall deficits could quickly disappear. That is a wild card in this forecast. So, keep that in mind.
The following maps are from the Climate Prediction Center and give you some idea of what other forecasters are thinking. One wild card, as we have been discussing over the last few weeks, in this type of active tropical pattern would be a tropical system moving up through the Gulf of Mexico and bringing us much needed rainfall.
Temperature Forecast Map
Click the map for larger view
Rainfall Forecast Map - Indicates Below Normal Rainfall
Click the map for a larger view - you can see the probabilities for dry weather are centered over our counties.
Overall the analog years chosen for the fall forecast period, on the maps below, seem to indicate the most likely scenario that will unfold for our local region.
Click for large view of the temperature and precipitation forecast for September through November.
And a couple of more analog maps (analog means the years that most closely match the current ocean conditions and other factors)
Temperature Forecast For September - November (click for larger image)
Analog Precipitation Forecast - Shows Dry Conditions For The Fall Months
(Click image for larger view)
As you may know our region is currently experiencing drought conditions. Unfortunately, this is expected to worsen in the coming weeks and months. Forecast charts are indicating that below normal precipitation will likely be the case for September through November. Again, the wild card in this forecast would be any tropical storms or hurricanes that advance through the Gulf of Mexico and move up into the Tennessee and Ohio Valleys. If this were to occur then we would likely see a period of moderate to heavy rainfall of a more widespread nature. However, that is a wild card and too uncertain to actually forecast at this time. You will have to follow the tropical updates as the hurricane season unfolds.
Otherwise - the general pattern will favor below normal rainfall. Not what we want to hear. This could enhance the fire season in our region. There are hints that precipitation may be above normal from mid winter into late winter - but we are getting ahead of ourselves as this post is talking about fall!
The following information is an exert from a neighboring National Weather Service Office
Large Scale Synoptic Pattern
A healthy La Nina continues to evolve over the eastern and central Pacific (the most
recent weekly Nino 3.4 SST (Fig - 1a, b) has already dropped to about -1.1C as of mid Aug).
According to the Climate Prediction Center /CPC/, “most dynamical models generally
predict a moderate-to-strong La Niña, while the majority of the statistical model forecasts
indicate a weaker episode (Fig – 2). Given the strong cooling observed over the last several months and the apparent ocean-atmosphere coupling (positive feedback), the dynamical model outcome of a moderate-to-strong episode is favored at this time. Therefore, La Niña conditions are expected to strengthen and last through Northern Hemisphere Winter 2010- 11”. The CPC Fall Outlook can be found here.
End of their comments
This charts shows the developing La Nina with below normal
water temperatures through the winter. The normal baseline is
the zero line in the middle. Anything below that line means
colder than normal water.
And an easier map - you can see that the Pacific waters are colder than they should be on the map below. This is what a La Nina looks like when you are looking at water temperatures. Below normal waters in the Pacific basin.
In layman terms La Nina simply means that the Pacific waters are going to be cooler than normal - last year we had an El Nino environment. Warmer than normal ocean waters. That was not the only atmospheric condition that influenced our winter - far from it as a matter of fact. There were other contributing factors that helped us end with the sixth coldest winter on record.
Let's take a quick look at the water temperatures from last year and compare them to this year - check out the Pacific - you can see the dramatic changes.
Above - September 2009 water temperatures (note the El Nino conditions in the Pacific Ocean)
Above - September 2010 ocean water temperatures (see how much blue there is - blue is cooler than normal water temperatures)
I don't see much to argue with or disagree with on the subject of La Nina and the upcoming fall season compared to what other forecasters have been stating. I have been discussing this issue for months in my postings and email forecast analysis - along with my posts on Facebook - so have some other forecasters. And those thoughts have changed very little.
For sensible weather all of this will mean that the fire danger will continue to increase in the coming weeks and months. September through November will bring the normal windier conditions and lower humidity levels. This coupled with on-going drought conditions in our region will mean a greater fire danger.
I suspect local fire departments will be quite busy in the weeks and months ahead. Our best hope is that a tropical storm or hurricane will move up out of the Gulf of Mexico and spread beneficial rains into our region. Of course the Gulf Coast residents do not want that to happen. The good and the bad of tropical weather. They benefit some and hurt others.
NOAA has also issued their drought forecast - you can see that our region is included in the outlook. Click image below for large view (thank you Paducah, NWS for posting this information)
The tropical season is expected to be quite active in the coming 6-8 week period. Numerous named storms will likely impact the Atlantic basin. Each one of these will have to be tracked and monitored for possible impact to shipping lanes and U.S. coastlines.
We are also quickly approaching our second severe weather max. We normally have a max in spring and fall. Although, severe weather can happen anytime of the year - including winter. This may be especially true this winter with the La Nina pattern developing. La Nina sometimes can increase the risk for severe weather over the central and southern United States during the fall and winter months.
If you would like to read additional information on the upcoming fall and winter forecasts then visit the links below
Central Illinois - National Weather Service
Southeast Lower Michigan - NWS Outlook
And - on a final note - one of the model suites that I like to use for seasonal forecasting is showing a warmer than normal winter for our region. The below map is for December through February. Still some time to sort out the winter thoughts. :) But, that is a preview.
Winter temperature forecast (from one model suite)
I would not be surprised to see the primary storm track north of our region this winter - thus putting us in the battle ground for severe weather potential. A storm track to our north would provide areas from Kansas into Iowa and northern Illinois/Wisconsin/Michigan with plenty of snow and ice. I would expect our region to have frequent swings from above normal temperatures to below normal temperatures. The proverbial battleground could be quite common across our region. This would be unlike last winter when we saw mostly below normal temperatures and consistent/persistent cold.
I have also stated that I believe the risk for a significant ice storm (1"+ of freezing rain) will be above normal from Oklahoma, eastern Kansas, central/northern Arkansas, Missouri, southern Iowa, Illinois, Indiana, northern Mississippi, Tennessee, Kentucky, and southern Ohio - a corridor along those lines.
In any given year the risk for a significant ice storm is about 1-5% (depending on your location in the area mentioned above). As stated above it is impossible to predict exact/specific events months in advance. It is only possible to forecast patterns. In a normal year our region experiences some freezing rain - 1 or 2 episodes. Normally accumulating less than 0.25".
If La Nina ends up being one of the primary weather influences this winter then a strong and active northern jet is likely. Lot of storm systems - lot of cold fronts - quite a bit of active weather. The question will come down to where the battle lines set up between the warm and cold. Seems like that is usually the case in this region.
If also appears that the NAO has a better chance of being neutral or positive during this upcoming winter. Another important clue as to how our winter unfolds.
In layman terms - warmer than normal winter appears likely for our region. Above normal precipitation - esp January through March. Frequent/strong low pressure systems passing to our north (this would keep us in the battle zone for rain, snow, and ice). Potential for one or more severe weather episodes will be fairly likely. Several significant cold waves where temperatures fall below 10 degrees - but transient in nature. We will likely see some impressive temperature swings with a pattern that appears to be unfolding. Impressive meaning temperatures dropping from the 50s or 60s into the teens and 20s after frontal passage.
That would mean a winter of extremes - wild temperature swings. From milder air to colder air - strong cold fronts - deep storms in the central United States. However, our region is fairly used to this type of weather in the winter.
There are also a number of signals that are pointing towards much below normal temperatures, for the Alaska months, over Alaska and western Canada, northwest United States into the northern Rockies. Some of that bitter cold air is likely to spill into the Great Lakes and central parts of the United States during the winter months - which in itself isn't unusual - but what might be unusual is just how cold some of those temperatures spilling in from the northwest might be. Something for us to watch.
We still have some time before I come out with my official winter thoughts. We did pretty well last year with the predictions for a cold and snowy winter. We will see how this winter unfolds. Of course it only takes one or two big events in our region to make for a memorable winter.
- Beau Dodson
Proudly serving western Kentucky and southern Illinois
Meteorologist for the McCracken County Office of Emergency Management
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