SUMMER PREVIEW -- 25 MAY 2004
The latter half of SPRING 2004 bears a striking resemblance to the SPRING 2003. The critical question is whether the pattern flip flop that occurred in Mid July 2003 to a HOT dry pattern over the Plains and Midwest in 2003 will occur this Summer... and when.
Given the number of atmospheric similarities between APRIL / MAY 2003 and APRIL / MAY 2004 it is tempting to forecast a repeat of a similar type of Summer ( that is the rainy pattern holding over the Plains and Midwest until early July and a lot of heat over the Rockies). However there are some critical differences that Must be considered..
The severe drought over the Western US (recall last summer's record Forest Fire season) --- is part of long term on going 7-10 year cycle. This past winter of 2003-04 and SPRING 2004 has seen good rainfall / snow over the Pacific NW while the Rockies have stayed in the drought.
IN the SPRING of 2003 it seemed that a La Nina event that was developing... and as such would bring Above Normal temps and dry conditions overt the central and eastern US. However the event collapsed suddenly in late May and June 2003.... which allowed the Wet pattern over the Plains and Eastern US to hold into Early July. This year the forecasts from many weather sources call for Neutral La /El Nino conditions in the equatorial Pacific Ocean.... but in fact a weak non forecasted La Nina event might be developing.
Another major difference between this year and last...is that the Excessively wet conditions that developed in the winter of 2002-03 over the Eastern US continued throughout the Spring of 2003. This set up a trough or dip in the Jet stream that kept the central and eastern US either Normal or Below Normal temps and Above Normal rainfall until Mid July 2003 . At the same time the long term drought over the Western US allowed a strong Ridge to build over that area... which suppressed rainfall and gave Above Normal temps (hence the term drought begets drought)
While the winter of 2003-04 and Spring 2004 saw the continuation on the long term drought over the Western US (except for the Pacific NW coastal areas) conditions over the Eastern US are significantly different. Through the SPRING 2004 season conditions over the Eastern US-- especially over the southeast states-- are MUCH drier than what we saw in 2003. In fact the building Dryness may reach DROUGHT levels over GA SC NC and this area will be expanding into lower VA eastern TN and AL as the early Summer 2004 develops. This CURRENT increasing dryness over the Southeast will interact with the western US dryness / drought and produce a much different pattern over the central and eastern US this summer.
JUNE 2004 will likely start off as a continuation of the MAY 2004 pattern. That is to say a fairly wet and stormy pattern because of the high amounts of Blocking in the Jet stream over eastern Canada and Greenland. By Midday Month some of this blocking will have weakened allowing for a warmer overall pattern in the Plains and Midwest. The Pacific NW stays cool. The development of La Nina which would come as a surprise to some will have to be Monitored.
JULY 2004. The Increasing dryness over the SE states will begin to link up with the Ridge over the Rockies. These two features will force the trough over the Great Lakes and /or Northeast US to Lift out and weaken which in turn will shut off or reduce the Rainfall amounts over the Midwest and Northeast US. .
AUGUST 2004 Given how far out in time this is the confidence rate will be Low. But If the dryness over the SE states does develop and expand inland then Much of the deep south and Midwest could see a very hot and very dry Month.
2004 FORECAST MAPS
Click on the Maps for LARGER View
|JUNE 2004||JULY 2004||AUGUST 2004|
|JET STREAM||TEMPS & PRECIP||JET STREAM||TEMPS & PRECIP||JET STREAM||TEMPS & PRECIP|
WHAT COULD GO WRONG
Be sure to check back later Friday Friday night and Saturday for more detailed explanations forecasts and ideas
|1. REVIEW OF WINTER 2002-03||2. USE of ANALOGS|
|3. Is there an El Nino Coming?||4. Current ENSO conditions|
|5. WXRISK ANALOGS||6. SOI|
|7. MEI||8. QBO|
|9. CLIMATE MODELS||10. AUTUMN SNOW COVER|
THE USE OF ANALOGS
Many (but not all) forecasters use "Analogs" to help make a seasonal or monthly forecast. In weather forecasting the use of analog is an attempt to understand the seasonal forecast period based (in past) upon similarities between a particular set of parameters. The idea is by searching for similarities with other years or seasons it gives a forecaster some clues as to how the monthly or seasonal forecast may develop. .
For example one may consider the fact that most US winters during strong El Nino years bring warm and dry conditions to the Upper Plains and Midwest and rather wet and cool conditions to the Deep South and changeable conditions in the Northeast. Or a forecaster may look at say the past 6 months... 12 months... or 18 months worth of temperature and precipitation data over a certain section of the country and use those similarities to the the current situation to assist them in making the monthly or seasonal forecast.
Done the correct way the Analog method has validity to it. For example to simply assumed that all El Nino events produce ONLY one set of conditions in the winter months is of course folly. Some of the most severe winters in the last 100 years have been El Nino winters and likewise.... some of the most Mild winters in the last 100 years have also been El Nino winters. Some forecasters and weather hobbyists hold the view that analogs are not very helpful since weather records are incomplete or not sufficient enough to be considered as an indicator of what the upcoming seasons might hold. For most locations temperature and precipitation data only extends back 100 or 130 years and accurate Upper Air maps only go back 70 years at best . That argument is Valid and ANY seasonal forecast using analogs that is based on ONE parameter is very risky and has a high degrees of failure built within the forecast.
One way of getting around this is to use several factors parameters and cross matching the analogs to look for common ground.
Just like the last several seasonal forecasts I will use these parameters and in this order of importance
SPECIAL REPORT FROM WXRISK.COM--
Already asked to 10 years there has been some significant
improvements in the development of seasonal climate models and their skill level... which
basically is a fancy scientific charm that is used to describe the accuracy all the
NEW SUMMER CLIMATE MODELS SHOW SIGNIFICANT CHANGE TO A HOTTER
AND DRIER THAN NORMAL PATTERN
Climate models have been in existence for over 20 years but for most all of their existence they have been of such poor quality that long-range forecasters often either discount them completely or give them a very little if any credence. However since the mid-1990s with the development of ensemble forecasting the climate models had been improving steadily each year by small incremental amounts. As we enter the middle portion of this decade some of the pine models had been showing fairly decent still over a thirty day and 90 day time frame.
(ClickHERE to see what ENSEMBLE forecasting is and why it is sooooo important and Useful!)
Even so one must be careful in using climate models. It is a little like giving whiskey and car keys to teenage boys.... An over reliance on the Climate models can lead one to disaster in terms of weather forecasting and potential trading positions. It is important that only forecasters with experience in explaining the model bias and tendencies use these models. I have been using climate models for several years and I have considerable skill in this area and I believe it is one of the reasons I've been pretty good with my seasonal forecasts over the last several years.
One of the primary climate models over the last several years has been the AGCM. (AGCM
stands for atmospheric global climate model). The
AGCM is run the beginning of every month and a consists of a 20 member ensemble not just one climate model. The AGCM has been in existence and running every month since 1997 but only over the last few years has the model shown any skill at all.
The AGCM has several very important biases which must be analyzed and taken into consideration before issuing a ANY seasonal forecast. One day there may a climate or seasonal model which is accurate and skillful enough so that the biases do have to be pointed out and a more reliable climate forecast can be considered.
The AGCM has a serious cold and WET bias. This bias exists within the model because the AGCM is essentially an extension of the long-range American model which also is famous for having a cold and wet bias after day 7 towards developing large areas of storminess and precipitation.
Here are some older but recent runs of the A CM model which clearly show the
1 )severe cold bias of the model and
2) its inability to show ANY sort of significant heat at ANY time of the year
3) the AGCMs inability to show any sort of prolonged dryness in either Canada or the United States.
NOVEMBER AGCM for the period of N-D-J 2002-03As you look at these AGCMs keep in mind that the TOP map is the Actual depiction of what was going on in the three-month period .... And the bottom map is the model depiction or forecast of what the three-month period was supposed to be like.
*** click on the maps and they will enlarge ***
THE HOT MIDWEST SUMMER OF JULY and AUG 2002.
For those of you that cannot recall the months of July and August 2002 placed in the top 10 hottest July August months on record for the Midwest. As you can see from these examples JUNE and JULY 2002 -- the three month period of JUNE JULY AUGUST 2002 was a hot and dry month across most of the Rockies... the central & Upper Plains and into the Midwest. Yet the June and JULY AGCM runs showed no HEAT of any kind of across the CONUS.As you look at these AGCM models keep in mind that the TOP map is the Actual depiction of what was going on in the three-month period .... And the bottom map is the model depiction or forecast of what the three-month period was supposed to be like.
*** click on the maps and they will enlarge ***
Do You see a pattern developing here with this Model? You should.
In this next set let take a brief look at the AGCM from LAST SUMMER.....
For those of you that cannot recall the months of JUNE and JULY 2003 were very hot over the Western US with a record dry and Hot period that lead to the worst Fire season ever while over the Eastern US it was rainy and cool. Then in late JULY the pattern switched and AUGUST 2003 turned out to be one of the driest AUG over the Midwest ever.
The AGCM run from the month of MAY 2003 depicted NO heat at all ANYWHERE across the CONUS when in fact there was a large area of Above Normal temperatures over the the western US. This pattern continued through July of 2003... and even more so in the month of August. We can see in actuality that August 2003 showed huge areas of much above normal over the entire western United States by the model forecasted almost no significant deviations from above or below normal with regard to temperatures anywhere in the US or Canada.
*** click on the maps and they will enlarge ***
Because of the AGCM's appalling cold bias forecasters have been working on a new climate model over the last two years. This model has been showing significant improvement in its ability to forecast conditions reasonably accurate out to 3 and 6 months.
Below is a comparison of the April AGCM and its temps depiction for the period for the Summer and Autumn 2004... and in the right column... the New improvement climate model (called the SFM). I have highlighted a PURPLE line over the maps to show the models depiction of the Jet stream.
As you can see there are 4 maps -- the Upper left map is MJJ-- the Upper right map is JJA --the Lower Left is JAS -- . the Lower right ASO. The beginning of the summer -- MJJ ( may June July) appears to show a large area of Below Normal temperatures covering much of the Upper Plains Midwest and into the Ohio valley ( ECB) s which implies a fairly deep trough over the middle portion of the nation. This pattern appears to continue into the heart of the summer (JJA).
Looking at the new climate (the SFM) in the right column we see a much hotter pattern developing in the first half of the summer over the heart of the Midwest which continues into the JJA period. In fact the model implies that there may be some sort heat dome developing over the Midwest by middle portions of the summer.
*** click on the maps and they will enlarge ***
However last Friday a significant change occurred in the climate models .
Here is the June forecast from both the May AGCM and new SFM climate model. The AGCM show a very hot for the month for June and it is arguably the hottest summer month I have ever seen from this model since I have began following this model back in 1998. The more reliable SFM model is not quite that hot but it is significantly hotter than it was and the region of cool temps have shrunk and shifted to the Upper Plains.
Looking at the new climate model of May 2004 for the SUMMER the May 2004 AGCM suddenly made a dramatic shift in its depiction of temperature patterns across the Plains and Midwest for the Summer of 2004 . As I stated above the March and April AGCM show a fairly cool and wet pattern across the Plains and Midwest this summer. However the new MAY 2004 AGCM showed a complete reversal of that idea with large areas of Above Normal temperatures developing across the Midwest. In fact the MAY 2004 AGCM forecast for the heart of the Summer is the WARMEST summer pattern this model has ever depicted -- however keep in mind that the AGCM only goes back to 1998.
We see that the new Climate model is not only consistent with what it WAS showing in March and April but the area of Above Normal temperatures over the Midwest and eastern Plains is in fact increased -- in terms of area and intensity.
*** click on the maps and they will enlarge ***
This is why the May 2004 climate Models are significant. First even
the colder bias AGCM is significantly warmer than what the Model was showing in March and
April. Second the MAY 2004 AGCM is the hottest summer forecast this model has
ever produced. Third the AGCM has Moved Towards the new and better
climate model ( the SFM)... which tells me that the SFM is again outperforming the AGCM
(which it should)! Fourth the Jet stream -- which again I have superimposed on the maps
with the Thick purple line -- shows a trough over the West Coast of US
and the Ridge over the eastern Rockies Plains and Midwest. This is supported by the developing drought conditions over the Rockies and deep South as well as the developing sea surface temperature patterns in the Pacific Atlantic Ocean. In other words this may 2004 forecast makes sense... whereas the March and April 2004, models were not.
Here is the temperature forecast from the May 2004 AG CM for the summer. It has a large area of very dry conditions over the Middle Atlantic region into the southeastern states and normal rainfall over the Plains and Midwest. However as are shown above the model always under does the dry areas because of the cold and what bias. Thus I suspect the area of Below Normal rainfall over the southeast to be much larger and press into a good portion of the Midwest. In fact the rainfall forecast from the new climate Model shows a drier pattern over the Lower Midwest.
SUMMARY -- WHAT DOES IT MEAN DT?
The sitaution has to be watched very carefully.... and it has major implications for the Grains and Energy. BUT just like last Summer it is imperative that one does NOT Jump the Gun. For example early Last summer both in the original Summer forecast and the Mid Summer Update I went for a WET and seasonal JUNE and JULY and a much drier & Hotter AUGUST. I received a steady stream of calls from folks wanting to know when the pattern shift was coming... almost beggiing to go public with the pattern shift forecast coming.
The point is that IF the wet pattern of May 2004 does end It Might end by Memorial Day or June 3 or June 13 or June 23rd. I will watch it closely and stay on top of it.... I believe that when and if this summer pattern does develop.... No oine will get you that weather info faster than I will.
WHAT ARE THE "ENSEMBLES" & WHY ARE THEY IMPORTANT?.
Weather models are based on something called GRID points. In other words
weather models are essentially a elaborate game of CONNECT the dots!.
Each of these grid points or DOTs represents data that goes into the weather model's equation and programs. The closer the "dots" or grid points are
together... the better the data and the more likely it is that the Weather model to be close to "REALITY" .
This data in the Grid points is derived front several sources.... such as weather balloons pilot reports satellite data etc
That is why we call them MODELS. The KEY point YOU must understand is that there is ALWAYS going to be some data that does NOT get into the computer and model equations. So the Models have to ESTIMATE what the missing data is. Sometimes these estimates are really good.... and sometimes they are really bad. For instance over the Pacific Ocean there are few land stations to report Real data so the models have to use satellite reports and estimated data to fill in the blanks or gaps.
Now suppose one day the American model shows Big storm developing over the northern Pacific Ocean over the next 2 or 3 days and has the Low pressure area hitting Seattle in 6 days. The first model run is called the OPERATIONAL model. No matter what happens the weather forecaster must ask himself "what is the reliability of weather scenario this model is depicting ? " The best and oldest known way is to ask if the weather model "solution" makes meteorological sense.. So if the model says it is going to snow in Chicago 3 inches in early May -- that solution is NOT likely to be correct.
But back in the 1990s with the rise of advanced computers it was realized that you can use the new computing power to run the same model over and over again. The result is a spread of solutions NOT just one. Hence the term "ENSEMBLE" . So lets say you have 20 versions or MEMBERS of the American or Canadian weather model along side the operational Model run.
Now lets go back to that hypothetical storm that the model shows hitting Seattle in 6 days. With the Ensemble a forecaster can now compare the Operational Weather Model to the other members of the Ensemble. This gives a forecaster a degree of certainty and probability that did NOT exists before. Thus in our case.... while the Operational Model shows the Big Low hitting Seattle in 6 days but 10 other versions of the ensemble show NO storm at all... and 8 versions show only a weak cold front... the forecaster can say with Much higher confidence that it is unlikely a Big storm will hit Seattle in 6 days.
Or on the other hand the Operational American weather Model is famous for developing whacky weather scenarios after day 7 in North America. It may show a Hurricane suddenly developing in the Gulf of Mexico. By using the ensemble the forecaster can get a good idea of whether such a scenario even possible or likely.
The American model ENSEMBLE has 21 members and is run twice a day out to 16 days... but the grid point resolution ( the DOTS) are spaced fairly far apart. This model is undergoing an upgrade. The Canadian Model also has an ensemble which features 17 members that run out to 10 days but it is only run once in the early morning hours. The European weather model ensemble has 51 members and has the best resolution of any of the Medium range weather models and is available in the pre-dawn hours and again around 11am CDT. The Navy model has a 9 member ensemble out to 10 days and is run once in the early morning