SPRING 2010 FORECAST
The SPRING season of 2010 will feature large areas of Below and Much Below Normal temperatures especially east of the Mississippi River and large areas where precipitation will run Above and Much Above Normal. It will be every bit as wet and as chilly as what we saw in the Spring of 2009. In fact this will make for the third consecutive Spring season which is featured colder and wetter than normal conditions across much of the CONUS.
These maps below give a summary of monthly conditions for the next 90 days.
There are several factors to be considered in making this Spring 2010 forecast. They are:
We are still in a El Niņo event which began in the late Summer early Autumn of 2009. The current El Nino event did briefly reach " strong" El Nino criteria during the early portion of the winter. However for the past 45 days the El Niņo event has been in the stuck at "Moderate level". ENSO events are judged or categorized by their intensity across the various ENSO regions. As you can see from this diagram... the ENSO regions consists of several regions along the equatorial Pacific from the Peru Coast... Region 1 Region 1 and Region 1+2... then westward toward the international date line.... Region 3 Region 3.4 and Region 4.
While the different El Niņo regions are important in understanding how it particular El Niņo event is different from previous ones and how they are similar... the criteria used to judge whether or not a El Niņo or La Niņa event is underway is ENSO region 3.4.
This image shows you the
recent track of the various El Niņo regions since early February...
and as you can see the ENSO region 3.4 has held steady at around
+1.2C. There had been some wild fluctuations however in ENSO region
1 ENSO region 2 and ENSO region 1+2.
This image is the current El
Niņo event across the equator with the warmest sea surface
This image here shows the subsurface temperatures of the El Niņo from the surface several hundred meters down. As you can see the bright yellows and Orange colors... there is a lot of very warm water that is still more than 100 m below the surface. As long as we see this sort of impressive large areas of very warm sea surface temperature anomalies below the surface... any weakening of the El Niņo is going to be slow to occur.
The data of all ENSO events since 1950 shows a strong correlation between wetter and colder than normal springs over much of the central and eastern US and Moderate El Nino events. Of that there is little to debate. The real issue is what's going to happen in May of 2010. If the current El Niņo event weakens enough by the time we reach may the pattern may turn milder and drier.
Indeed some of the forecast models have been showing that the El Niņo is going to weaken later on the Spring. Undoubtedly that will happen but it's probably will occur slower than what the computer models are showing.
This image represents the European model ENSO forecast which came out in early February.
As you can see the model shows steady decline in the warm SSTAs in March and April but as I pointed out the actual temperatures have not dropped off much at all or so it seems to me that this model projection for cooling of the El Niņo event is not likely to occur.
This image comes from the IRI in the middle of February. As you can see it is a compile edition of 20 different models and all of them show the El Niņo event weakening. So therefore confidence is pretty good that is going to weaken as we go later into the Spring and by the time we reach the Summer 2010 most of the Model data shows either neutral conditions or actually a weak La Nina developing. However it appears based upon the recent data that I showed above that once again most of these models are weakening the current El Niņo event to rapidly.
Indeed the most recent update of the CFS -climate forecast system -- from CPC shows a much more gradual weakening of the El Niņo event with no real drop-off in the warm sea surface temperature anomalies until April at the earliest.
TheQBO (quasi-biennial oscillation) is a oscillating band of strong winds that exists at the top of the atmosphere all around the world. The QBO blows in east or negative phase for several months... sometimes as long as 9 to 15 months... then moves back towards Neutral.... then in the positive phase for 9 to 15 months... then back towards Neutral. The QBO phase ( +QBO or -QBO) influences the amount of High latitude Blocking in the Jet stream... the strength and intensity of the Pacific Jet stream... and African rainfall which is an important aspect of hurricane seasonal forecasting.
As this link shows the current QBO is in the negative or EAST phase and continues to increase in the negative or easterly values as they come out of the winter into the spring. This means that during the spring months we can anticipate the QBO to reach a value of at least -20 at some point over the next few months. The current -QBO has been in the easterly phase for last eight months so the probability is pretty high that the QBO is going to remain in the strong negative phase for several more months. The strong negative values of the QBO could also have some significant impact on the hurricane season as well .
PDO - Pacific Decade Oscillation
Over the last 10 years there has been a significant amount of research done on a longer term Climate pattern that is called the PDO in the weather biz. The PDO or "Pacific Decadal Oscillation" a long-lived climate pattern that exists over the northern Pacific Ocean.
The PDO involves the location and intensity of large pools of warm and /or cold Seas Surface Temperature anomalies (SSTAs) in the central and eastern areas of the Northern Pacific. Why is this important? Again research has shown that large areas of warm and cold water pools called SSTA couplets STRONGLY affect the Jet stream pattern and the positions of Ridges and troughs within the Jet Stream over the Pacific and western North America.
This is diagram shows you the Two phases of the PDO... the BLUE color represents very cold SSTA... the Green cool SSTA.... the RED color very warm SSTA and the Yellow warm SSTA.
The typical or classic large-scale cold weather pattern from October through May features a rich in the jet stream over the West Coast and a trough over the eastern US. This pattern in the weather business is referred to as a +PNA. Sometimes however we get a trough on the West Coast and original the Southeast. This pattern ...known as a -PNA in the weather business... often brings Below normal temperatures and excessive storminess to the western third of the CONUS and can bring mild but stormy conditions to the Plains and Midwest and mild and fairly dry pattern for the Southeast and middle Atlantic states.
It has been determined by extensive research that when the PDO is in the Positive or Warm phase .... there is a buildup of warm water anomalies along the West coast of North America... this often leads to a +PNA or cold pattern. On the other hand when the PDO is in the negative or cold phase... the buildup of cold water anomalies will cause a -PNA pattern to lock in and the trough develops over the western US instead of the East Coast.
For most of the winter the PDO has been either neutral or slightly positive. We have had some ridge along the West Coast for a good portion of the winter but it has not locked in and at times the ridge over the West Coast is broken down. When that has happened -- in January of 2010-- the cold air supply into the central and eastern US and Canada came to a screeching halt.
Predicting the PDO phase can be very hard to do and there is no sure fire way to do this. The history of the PDO is such that the Spring season phase of the PDO is almost identical to that of the previous Winter. If we operate on that assumption I can forecast a near neutral or slightly positive PDO for Spring 2010. This means that at times there will be Ridge in the Jet stream over western Canada and a trough over the central/ eastern Conus for a significant portion of the Spring.
AO - Arctic Oscillation / and other high latitude blocking features.
The AO is a term used describe and measure Blocking patterns in the Jet stream over the Arctic region. Typically most weather patterns run West to East. In the weather Biz the term "Blocking" refers to a portion of the overall weather pattern that has "blocked up". In other words the typical weather pattern movement is not occurring. Strong Blocking patterns can sustain themselves for days or weeks. When the Arctic Oscillation is in its negative phase a Ridge in the Jet stream over the Arctic regions forces the severe cold air masses out of the Arctic region southward and can reach the Central and Eastern CONUS (as it did many times this winter) and into portions of Europe and parts of Asia.
In OCT of 2009 we saw record early cold over the Plains and Midwest with early frosts and freeze over many areas. The Oct 2009 AO value was the most negative ever record for OCT. The AO turned Neutral in NOV then turned sharply Negative in DEC 2009 Jan 2010 and FEB 2010. In fact the 3 winter months of DJF represent the most strongest sustained Negative Phase ever record in AO.
There is no certain way in determining what the AO phase is going to be during the spring months but all of the data over the past 50 years suggests that the predominant phase of the AO in the winter months is often the dominant phase in the early portion and middle portions of the following Spring season. If we assume that is going to be the case for the Spring of 2010 then we are going to see a season like the last several Spring seasons (2009 2008 and 2007) where there is a lot of high latitude blocking in the jet stream which forces the cold air for the South than normally might reach.
SOIL MOISTURE -- just what it says. Large areas of excessively wet or dry ground can often have significant impact on where the Mean Ridge / trough positions will set up during a season.
This is probably one of the most overlooked aspects of forecasting and a lot of seasonal forecasters did not consider the soil moisture issue as a significant factor despite the overwhelming amount of evidence that it clearly is.
You may have heard the old adage that drought begets drought and wet patterns to get wet patterns. It turns out that a lot of truth to that. Large areas of excessively dry hot grounds will often feedback energy into the atmosphere which in turn affects the overall pattern in the region. This process is known as a positive feedback. In a similar vein large areas of excessively wet grounds large areas can also affect the pattern by developing a persistent trough over that area.
Lets see how this works:
This link shows the soil moisture map from late November of 2009 As you can see the large areas of dark greens and blues showed huge areas of excessively wet soil conditions by late in the Autumn.
This was really a continuation of the excessive soil moisture conditions from back in the Summer of 2009. Not surprisingly the Summer of 2009 was the coolest on record for much of the Midwest but especially over IA ILL and IND. The Autumn as we know was excessively cold and wet over much of the Plains and Midwest because the mean proposition held over the Mississippi Valley. With the mean trough position located there much of the Plains and the upper Midwest saw record cold temperatures in October.
As we can see from this image the excessively wet soil conditions had not really change by the end of November. If anything the region of excessively wet conditions had spread eastward. And as we now know the winter of 2009 -- 10 big feature a persistent trough over the Midwest and East Coast... which is one reasons why it has been so cold and so stormy.
This image shows you the latest soil moisture maps both short-term and Long-term. As you can see not much has changed over the Winter of 2009-10. To see such a persistent and large area of the central and eastern US with excessively wet soil conditions since last summer is a strong indication... about as strong as indication as one can have... that the pattern is not really going to shift much during the early Spring season. Unless there is some sort of significant change the overall pattern it is likely that this mean proposition over the Midwest is going to continue into the late Spring and possibly early Summer months.
****** HURRICANE SEASON 2010 ****
Normally I do not speculate on the upcoming Hurricane season in the Spring forecast. There are too many other factors which have to be considered and we simply do not know enough about how the warm season patterns are going to develop. That being said I do wish to make two points.
First in early April Dr. William Gray's hurricane forecast will be issued and receive quite a bit media attention. In his forecasts which I consider to be the best in the business... he often include statistical probabilities for the upcoming hurricane season with regard to potential land falls in the Gulf of Mexico or the East Coast. Wxrisk.com strongly disagrees with the issuance and usage of statistics and forecasting landfalling hurricanes in the Gulf of Mexico and the US East Coast. Hurricanes and tropical storms may or may not make landfall as they approach the coastal areas depending on the overall synoptic pattern. They did not favor the East Coast or southeast coast or Gulf of Mexico region based upon statistical probabilities.
Second... the sea surface temperature anomalies in the tropical Atlantic and Caribbean are amazingly warm for early March. This image shows the current sea surface temperature anomalies for the Atlantic basin. As you can see there are areas which are over 2°C above normal across the central and eastern portions of the tropical Atlantic Ocean.
To show you how vastly different these temperature readings are for the tropical Atlantic here is March 2008. As you can see much of the tropical Atlantic is actually in the cold water (Dark Blue). Of course last spring we were still coming out of a Moderate La Nina so that is one of the reasons why the tropical Atlantic was so cold in early March 2009.
That being said if you compare March 2010 with the last several March SSTAs in the tropical Atlantic Ocean you will see that as of right now the EARLY March 2010 SSTAs are far and away the warmest in the last 10 years even exceeding the early-season warm that we saw in the Spring of 2005. It was this early-season warmth which was one of the reasons why the hurricane season of 2005 was so severe and record-setting.
As you can see from this image the sea surface temperature anomalies from 2005 in March were not very impressive. There was some slight warming in the tropical Atlantic were anomalies were over +1.5 degrees Celsius above normal and there was quite a bit of cold water along the Gulf of Mexico and southeast US coast.
By May of 2005 the warm water had spread to almost all of the tropical Atlantic c including the Caribbean basin but the very cold water continued over the East Coast and into the western Atlantic Ocean.
Of course there is no guarantee or even certainty that the amazingly warm ocean water temperature is now in the tropical Atlantic will continue. By the time we reach the end of May 2010 the super warm ocean were temperatures may cool off some. But if they do not ... and the El Nino weakens to Neutral conditions... the hurricane season of 2010 could be a pretty intense one.