SUMMER   FORECAST   2001

Click HERE to see the Winter 2000- 2001  forecast.
Click HERE   to see the Summer 2000  Forecast.

The Summer of 2001 is going to be a fairly active Summer weather wise with a number of Important contrasts.

This Summer forecast was Orginially released to the clients of WXRISK  in Middle May.  The forecast contains the WXRISK Summer 2001 Forecast as well as a review of what some of the other major forecast services are saying  and the Meteorological reasoning behind the WXRISK forecast and some Risk Assessment. A Non intensive Summer forecast will be  made available on on the web site for the General public over the next week but it will not contain nearly the information that THIS product  has.

The overall pattern will be one with the Mean trough  (or average) position over the HIGH Plains and Western Plains -- that portion of the US between the Rockies and the MISSOURI River and the  Mean ridge position will be located over the Southeast  states and the offshore waters of the Southwest Atlantic ocean. On the WXRISK  summer forecast maps... Temperatures (fig 1)   and Precipitation (fig 2) the Mean Jet stream position can be seen by the large PURPLE line... the dashed blue line is the mean trough position.

TEMPERATURES


temps1.gif (61488 bytes) 

With mean Jet stream position setting up as shown (the PURPLE Line) the Pacific NW will see Below Normal temperatures. WXRISK sees a large 500 MB trough located off the coast of Northern Br. Columbia  for most of the Summer  that will keep the Jet stream rather active across the Pacific NW... Northern Rockies and High Plains and perhaps the Northern Mississippi valley as well.  North of the Jet stream Temperatures will stay Below Normal.  The area most likely to see Above and possibly even MUCH Above Normal Temperatures is the Southeast US. This area has been in a prolonged 3 year drought   that has seen some recent improvement with the rains of the late Winter and Spring 2001. But the vast majority of climate studies show that there is a strong correlation between above Normal temperatures and drought conditions. In addition the latest grouping of Long range Climate models still show a significant drought right through the Summer 2001. (more on these models later).  In the areas between the Below Normal area and the Above Normal areas --- the central Plains... Central  Mississippi Valley... the Tennessee valley and the Ohio Valleys will see close to normal temps for the season.

Note that the WXRISK Temperature forecast is substantially different from the Official CPC  (Climate Prediction Center)   forecast for summer 2001. With respect to Temperatures  CPC has the below Normal Temperature areas located over the CENTRAL Plains Near Kansas City and St. Louis.

PRECIPITATION

precip.jpg (110144 bytes)

With mean Jet stream position setting up as shown ( the purple Line) The HIGH Plains will be the area mot likely to see Above normal rainfall this summer. The strong jet stream powered by a deep Upper Level Low off the Northern Br Columbia coast will bring in numerous systems into the Pacific NW. With the position of the strong Ridge over the southeast states at 500 MB... these Pacific systems will likely reach maximum strength  (go negative for those of a meteorological   orientation) over  HIGH Plains.  There is a 40% risk of seeiong Minor to Moderate Flooding over the Upper Plains and Upper Mississippi valley  ( SD ND MN IA WI)  this early summer.  Not 1993 mind you  but a good threat of excessive rainfall that can do significant crop damage.

Keep in mind  the Mean Jet stream position is a shifting moving  feature ...so at times during the summer the Jet will be a bit further east or west of the forecast position or even to the north or south. 

Over the Southeast... as stated above above.. the ongoing drought in that area (despite some recent rainfall over the Southeast)... will anchor a strong Ridge of High pressure in the upper atmosphere (at 500 MB). This will keep the southeast hot and dry.

The trickiest forecast as far as the precipitin forecast for summer 2001 is the Ohio  and Tennessee Valleys (The Eastern Corn Belt).   It is possible that the  ridge over the southeast US may expand North across the Ohio valley for  a few weeks or perhaps Longer.  IF this were to happen    IF ... the the Ohio valley (and the ECB) would turn appreciably hotter   and drier than the  WXRISK summer 2001 forecast.

SECOND HALF SUMMER FORECAST WILL BE ISSUED   JULY 4-5.

 

OTHER SUMMER FORECASTS  2001

C.P.C.   Climate Prediction Center

summer-outlook2001.gif (85713 bytes)  As you can see  CPC has the summer 2001 area most likely to see Above Normal rain over the central Plains... which I think is too far south.  The rest of the CPC forecast seems reasonable.

GWS  -- GLOBAL WEATHER SERVICES

summer01.gif (15479 bytes)   GWS 's summer forecast seems to be the opposite of the CPC and WxRISK forecast. The dry area ( the Yellow shaded area) is hard to see meteorologically speaking.

EARTH SAT  SUMMER  2001  FORECAST

GIFtoGIFServlet.gif (34036 bytes) The 4 Panel summer foreast from Earth Sat  Corporation seems more confusing than it is. The Left side is  Temperaturesa forecast. The Upper Left refers to the areas Above/Below the Lower Left refers to the actual mean temps.  The RIGHT side refers to the  RAIN... Upper right panel refers to the  Above/ Below Normal and the bottom right represents WSC forecasted rain amounts. From where I sit the Earth Sat forecast is fairly close to mine.


METEOROLOGICAL REASONING...

The mean or Averaging of the 5 main climate Models from NCEP's  CDC (climate Diagnostics Center)  branch gives us this   a) Ensemble Mean 500 MB pattern  June July August  fcst.z500.ENSavea.gif (13653 bytes) and    B)    Ensemble Mean 500 MB pattern July August  September fcst.z500.ENSaveb.gif (12964 bytes).

These models shows a fairly strong Ridge of HIGH pressure over the Southeast states while another ridge is located well Off the West Coast of CA.  Over NW  Canada... note the development of a deep 500 MB Low.  This feature when combined with the two HIGH pressure ridges creates a rather  Diffluent & strong Jet streak across the US Canada Border... and this is supportive of above normal rainfall for the Upper Plains and Upper Mississippi Valley. For the later half of summer  the NW Canada Low is still there but now there is a general weakens in the atmosphere  with a mean trough over the Rockies. Instead of  strong Diffulent pattern  over the US   Canadain Border  the amosphere seems much quiter.

The CCA Model  (aka the NCEP model) shows this development nicely; JAS  (July August and September) show the   2 mean troughs one over the Rockies the other over the SE states and the Gulf coast.

  1to3fcst.z500.CCA.gif (11532 bytes)   2-4fcst.z500.CCA.gif (11957 bytes)

CCM3

The April  CCM3 is presented here as part of the reasoning behind the Summer forecast issued in Middle May.  As of June 25 the CCm3 climate model has run in May and June. The CCM3  correctly showed the persistent trough over the pacific NW at 500 MB and the moderate temps over the Plains   --- in other words No major Heat pattern setting up for the Plains..

asst.mjj01.500ano.n_amer.gif (24789 bytes) pst.mjj01.500ano.n_amer.gif (29441 bytes)

ECHAM    from  APRIL

Did not make a whole lot of sense; the Model showed a ridge over the West coast of N.america  and Blocking or above normal heights over Hudson's Bay with little hint of any eastern US Trough.  The Blocking over the western US is over done since the first half of summer 2001 there was been a strong Trough over the Br.Columbia coast or just offshore.

pst.mjj01.500ano.n_amer.gif (24867 bytes)  asst.mjj01.2mtano.n_amer.gif (28332 bytes)

NSIPP  from April 2001

The Newest Climate Model the NSIPP   appears to have a great forecast at 500 MB from the April run. The pattern appears to be dead on.

asst.mjj01.500ano.n_amer.gif (25100 bytes)

AGCM FROM MAY 6

The AGCM is perhaps WXRISK's  Favorite or preferred Climate Model  as it did such a great Job  with the Winter 2000-01  forecast for Temperatures and Precipitation. The Summer months  ( June July August   and July Aug Sept)  appear to quite DRY  over the southeast and portions of the Southeast.  Temps over most of the US are depicted as normal.

 xprecip_us_current.gif (16750 bytes)  xstemp_us_current.gif (14305 bytes)   xz200mb_current.gif (27828 bytes)