Ag Weather Forum              09/16 09:37

   Between Two Jet Streams: Meandering Storm Bringing Rainfall to Central US

   A system that has found itself cut off from both jet streams across North 
America will only slowly move through the U.S. through early next week.

John Baranick
Staff Meteorologist

   The jet stream can generally be thought of as the storm track. It is where 
the majority of storm systems originate, and the movement of the jet stream can 
give you the basic idea on where those storms are going to track. However, 
under certain conditions, storm systems can either get cut off from the jet 
stream or develop from other means. Without a jet stream affecting their 
development and movement, their track can be erratic or wobbly and their speed 
is usually very slow.

   Such has occurred during this past weekend as two jet streams have split 
across North America. The stronger, northern one has found itself largely over 
northern Canada, while the weaker, southern one stretches from southern 
California through the Gulf. In the area in-between, several disturbances have 
found themselves, seemingly drifting slowly through weak steering currents.

   During the Sept. 12-15 period, one of those disturbances moved from the 
central Rockies into the Northern Plains and up through central Canada. Showers 
and thunderstorms were widespread as the system was able to tap into the 
abnormal heat and humidity in the driftless area between the two jet streams. 
The multi-day rain period produced some heavy amounts over 3 inches in some 
cases in the general region.

   But this isn't the only meandering disturbance out there. There is another 
that is currently found in the central Rockies. This one is forecast to move 
into the Plains today, Sept. 16. Like its predecessor, it should be a slow 
mover. These types of systems are not forecast as well as those tied to a jet 
stream, but the general forecast is for it to drift eastward into the Midwest 
during the weekend before getting pushed eastward early next week.

   Some areas will have four or more days of shower chances that could mean 
heavy rain. However, these types of systems are also ones that cause more 
sporadic showers and thunderstorms and are less organized than their jet stream 
counterparts. This makes the forecast difficult to pin down the "where, when, 
and how much" questions that are the most important for those of us on the 
ground.

   With that in mind, a general 1 to 2 inches of rain with pockets of heavier 
amounts are in the forecast for much of the Plains and Midwest west of the 
Mississippi River. The system moves a little quicker as it gets eastward during 
the weekend into early next week, and rainfall amounts drop down to more like 
an inch or less east of the Mississippi River.

   But with the multiple-day rainfall event, there are bound to be some areas 
that see much more precipitation than forecast. And similarly, the sporadic 
nature to the rainfall could mean some areas get completely left out.

   Those from Arkansas and Mississippi up through the Northeast, which have 
been on the drier side for the last six weeks or longer, have seen drought 
conditions rapidly increasing, bringing a poor end to the growing season for 
agriculture, and causing the water on rivers to fall to very low levels.

   That includes both the Ohio and Mississippi Rivers -- major transportation 
routes for the country. Some of this rainfall will undoubtedly help, especially 
for the Mississippi River, but it will not be enough to reverse the dryness and 
drought conditions that have quickly built up in the region. Much more rain 
will be necessary here, but the long-range forecast is not promising.

   To find more weather conditions and your local forecast for free from DTN, 
head over to https://www.dtnpf.com/agriculture/web/ag/weather/interactive-map.

   John Baranick can be reached at john.baranick@dtn.com




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