The Spring season of 2009 is going to be dominated by the three significant features
These features... along with a few other less influential factors will ensure that SPRING 2009 is going to be essentially a repeat of the cold Wet Spring the Plains and Midwest experienced in the SPRING 2008.
That being said let me state as clearly as I can that this .. and ALL private weather forecasts as well as those from CPC for the SPRING and SUMMER 2009 will be highly dependent on the current weak/ Moderate La Nina event.
Many of the forecast models are currently calling for an end to the weak/ moderate La Nina by late in the Spring / early Summer 2009. In fact some of these climate models are forecasting a weak El Nino to develop by the middle of Summer 2009. However since the current La Nina event was poorly forecasted by all of the ENSO climate models from just a few months ago there is a great deal of uncertainty as to whether or not the La Niņa event will hold on dissipate or actually become a weak El Nino event by middle of Summer 2009. In any event you need to keep in mind that a lot of these "early" SUMMER 2009 forecasts being issued in late February and early March are based upon some very risky ideas.
REVIEW OF WINTER 2008-09
The link below shows the WxRisk WINTER 2008-09 forecast. My Winter forecast was NOT a good one. Though DEC 2008 was cold east of the Rockies I was too cold. I was also too warm for JAN 2009 and too stormy with the pattern for the eastern CONUS for February 2009 ( I had way too snow) . On the other hand I knew by DEC 7 2008 that My Winter forecast was NOT going to work out where upon I issued a SPECIAL CLIMATE FORECAST STATEMENT on DEC 9.
Click HERE for WXRISK.COM'S WINTER 2008-09 forecast Maps
Sometimes meteorologists tried to make seasonal forecasting too much like rocket science or brain surgery. And sometimes there is a lot of uncertainty within the atmosphere with regard to the seasonal forecast and looking at long-term signals. But the spring forecast 2009 is not one of those difficult forecasts to make. The signals and driving influences are pretty strong. In addition we have the advantage of considering the previous spring of 2008. In many ways the atmosphere and ocean water patterns are very similar to what we saw in the late winter and spring of 2008.
The Winter of 2008-09 over the Upper Midwest and Upper Plains has been fairly close to what we experienced last Winter. If you recall the previous Winter of 2007- 08 it featured near record snowfall over New England and much of the Midwest and eastern portions of the Upper Plains. There were a number of factors which lead to this exceptionally snowy and cold pattern for the Midwest and since these factors did not change... the Spring of 2008 was essentially a continuation of the WINTER 20007-8 pattern. In other words very cold and very wet.
The factors that lead to such a
cold and wet Spring 2008 were for the upper Plains and Midwest:
As you will see throughout this discussion the atmospheric conditions entering the SPRING 2009 are quite similar to SPRING 2008. These first two imaged show the temperature anomalies.... since 1 JAN ... and over the last 30day. You can clearly see that temperatures have been running above normal for most of the Plains from SD into TX as well as eastern Rockies while over the Midwest especially east of the Mississippi River temperatures have run Below Normal.
These next two maps show you the precipitation patterns for current Winter ( 2008-9). The first one shows you the precipitation over the last 90 days... with a lot of very dry conditions over Texas and the lower Plains with a secondary area of dryness over the Southeast coast . There is also an area of Much Above Normal rainfall over the upper Plains. The second image shows you the 30 days . Note the increase in large areas of Below Normal rainfall from eastern PA down into GA and across the entire Gulf Coast and into the lower Plains and NM ... and the two areas of Above Normal rainfall... one over the western portions of the upper Plains and the other area covering much of Lower MO into the ECB.
SEA SURFACE TEMPERATURES: THE -PDO
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 SSTAs... the Green cool SSTAs.... the Yellow color represents warm SSTAs ... and the RED color very warm SSTAs.
Basically during the SPRING season ...a WARM Phase of PDO ... also called +PDO supports a Ridge in the Jet stream along the West Coast (warm & dry) ... a trough over the ECB and the Northeast (cold and wet) while the Plains is seasonal and dry.
During the SPRING season a COLD Phase of the PDO ... also called the -PDO supports a Trough on the West coast/ Rockies (colder/ wetter).... a Ridge over the Deep south or Southeast States (warm & dry)... more warm & dry conditions over the Lower Plains... a a stormy wet cold pattern for the central & Upper Plains and all of the Midwest into New England.
SEA SURFACE TEMPERATURE ANOMALIES SPRING 2008
In case you forgot this is what the SPRING 2008 looked like with respect to temperatures and precipitation . It was a COLD and WET SPRING.
MAM= March April May
WHAT ABOUT THE PDO RIGHT NOW ?
As you can see from these current sea surface temperature maps the SSTA (sea surface temperature anomalies) are very close if not almost identical to what we saw been the late winter and early spring of 2008. The large area of Cold sea surface temperatures in the eastern Pacific were directly associated with the negative phase of the PDO and the Moderate La Nina.
And for most of the Winter of 2008-09 going into this SPRING of 2009 again we see large areas of cold sea surface temperatures correctly associated with a strongly negative PDO event and Moderate but weakening La Nina.
This is one of the primary reasons why WXRISK.COM is forecasting a repeat of the 2008 Spring pattern for the Upper Plains and the Midwest for the Spring of 2009. Really it's not brain surgery. The same conditions bring about the same pattern.
WHAT ABOUT THE LA NINA ?
The biggest single uncertainty regarding the forecast for SPRING and SUMMER 2009 is the status of the Moderate/ weak La Nina event.
As I stated in the beginning of this discussion the redevelopment of the La Niņa event was a surprise to come climatologists and forecasters alike. This was the first time in many many years that we actually had the La Nina event redevelop during the winter months!
In many ways this current La Nina episode is similar to we saw in the Winter and Spring of 2008 but that event was somewhat stronger going into the Spring of 2008 than this current one. Even so by MAY 2008 that La Nina episode had greatly weakened and was essentially over with by the time we reached Memorial Day. Of course that played havoc with a lot of the summer forecast from many private agricultural forecasters since many of the SUMMER 2008 forecasts were premised on the idea that the moderate/ weak La Nina would continue right through the entire Summer of 2008.
Of course as we now know that did not happen.
The January and February 2009 weather patterns over North America are clearly under the influence of a moderate La Nina but this one does appear to be somewhat weaker than the La Nina episode of JAN / FEB 2008. The issue then becomes the rate of decline.
This image shows the forecast from the CFS Model.
The CFS is the official Climate forecast model used by the National Weather Service and the CPC -Climate Prediction Center. This model is popular and well-known by a lot of private energy and agricultural meteorologists but it is a pretty bad climate model as these things go.
For example... the CFS Model completely missed the developing La Nina event this winter and the poor performance of the CFS is one of the primary reasons WHY so many meteorologists and climatologists completely misread the Winter 2008-09 forecast. Recall that most of the private and government forecasts called for a milder than normal winter for the CONUS east of the Rockies ( which did not happen). Because everybody relied upon the CFS climate model the assumption was that there was not going to be a weak to moderate La Nina event during the Winter of 2008-09. This is important because there is a strong connection between colder than normal winter is and Weak La Nina events.
The point is.... that the latest CFS shows the weak La Nina episode dying and a shift towards a weak El Nino by the end of the Summer 2009.
However there are other climate models out there which good seasonal forecasters should be looking at and these climate models come up with a significantly different forecast.
This link shows you the latest computer models from the middle of February which are used to forecast La Nina and El Nino events out to 1 year.
This graph comes out every month and the important thing to note here is that this current chart clearly shows that MOST of the forecast Models do NOT end the weak La Nina this SPRING or EARLY SUMMER.
Many farmers and agricultural traders as well as agronomists know the old adage that drought begets drought and rainy patterns beget rainy patterns. There is a lot of truth to that and some sound meteorological reasoning to support those old adages and sayings.
Large very dry areas during the warm months of the year have what is called a "positive feedback". That is to say the hotter and drier the ground over a large area the more HEAT goes into the atmosphere which in turn feeds the development of any sort of Heat Ridge or Dome. In a similar manner... large areas of excessively wet ground often allow for the mean trough position to stay in the same general location which supports more additional rainfall and cooler temperatures... which in turn restricts the evaporational process.
Coming out of the Winter of 2007-8 the excessively stormy/ snowy conditions over the Plains and Midwest produced a large area of exceptionally wet and supersaturated ground conditions. This image shows you what subsoil moisture conditions look like exactly 1 year ago -- at the end of February 2008. The large areas of dark greens and dark blues speak for themselves.
23 FEB 2008
As I stated above there are SOME similarities between the late Winter / early Spring 2008 subsurface moisture to the CURRENT late Winter subsurface moisture conditions. This image shows the current LONG TERM drought map. The Long-term image shows a significantly wetter than normal subsurface moisture conditions over much of the central and upper Plains and into the Midwest / WCB.
and this image is the SHORT TERM DROUGHT map across the CONUS as of late February 2009.
In the Short-term image we can see conditions have not been nearly as wet over the last few weeks with most of the Above Normal moisture restricted to Upper Plains.
So in the general sense there is some similarity between FEB 2008 and FEB 2009 but there are also some important differences. Both the Short-term Drought Map and the Long-term drought maps show increasing areas of very dry conditions over much of the Deep South from Virginia into Texas. It is already well known that the Lower Plains (KS OK TX) has been experiencing an exceptionally DRY Winter and that is reflected in these maps. Over the last few weeks the very dry conditions have expanded into the Gulf Coast and up into the Carolinas and Virginia. WXRISK.COM believes this trend is going to continue and intensify as a moving to the SPRING 2009 and there is high probability of a drought of some sort of intensity being declared before the end of Spring 2009 over TX/ OK and possibly including much of the Deep South.
This assessment is based upon the continuing strongly -PDO along the weak La Nina effects combining to keep the current overall weather pattern in place right through the early Summer of 2009.
Any SUMMER 2009 forecast that is issued at this early stage is going to be a real crapshoot . In one sense I suppose that is true for any sort of long-range seasonal forecast . But sometimes the pattern is so strong obvious and locked in that a general forecast can be made. That is not however going to be the case this time around.
Since we have weak La Nina on going the first thing any forecaster has to do is figure out whether or not the La Nina will die off... hold ... strengthen or perhaps shift to a El Nino event. The wide disparity in the computer models at this early stage is really not going to help things.
In addition we have been in a strongly negative phase of the PDO for some time now. There is some possibility that the PDO may begin to move towards more neutral condition by late spring or early summer again at this point time that is really just a speculation.
The bottom line is that right now I do not have any strong indications of at about how the Summer of 2009 is going to shape up. I could easily see a scenario where the developing drought over the Deep South expands into much of the Midwest as the jet stream typically shifts to the north (as it typically does in the Summer months). On the other hand I can also see how the pattern might evolve into one where the drought stays over Texas the Delta and the Deep South and the upper Plains and Midwest stay fairly close to seasonal with regard to temperatures and precipitation.