Insect Migration Risk Forecast (IMRF)
2007 Growing Season
ACCEC (Analytical Center for Climate and Environmental Change)
Mike Sandstrom and Dave Changnon
Department of Geography
Northern Illinois University
DeKalb, IL 60115
wxtrw44@yahoo.com and dchangnon@niu.edu
Daily Forecast (updated Monday-Friday by Noon Central Time except holidays)
Forecast Release: Thursday, June 21, 2007, 11:30AM central time
Short-term (present to 48 hours):
Day 1 (Thursday 6/21/2007 noon to Friday 6/22/2007 noon): Relative Risk of Insect migration into the Midwest: LOW (10-15%): Greatest risk area is between US 136 and I-90 west of the Mississippi River and then southeast into Illinois and western Indiana west of I-65 to the east of the Mississippi River. This risk area includes central and eastern Nebraska, extreme southern South Dakota, southern Minnesota, Iowa, extreme northern Missouri, extreme southern Wisconsin, much of Illinois, and western Indiana.
Click Here For The Day 1 Risk Map (opens a new window)
The surface weather map this morning shows high pressure near the Ohio River in extreme southern Illinois and northwest Kentucky. A low pressure area continues to develop in eastern Wyoming with a warm front to the east of the low right along I-90 in South Dakota, extreme southern Minnesota, into central and southern Wisconsin. Two clusters of showers and storms are currently ongoing, one is over the Dakotas and another is primarily in northeast Iowa, southern Wisconsin, and extreme northern Illinois. Southerly or southwesterly winds are found across much of the forecast area, with the best flow especially west of the Mississippi River.
A rather active weather pattern is expected to continue across the Midwest for the next week or so. During the next 24 hours, the low pressure in Wyoming is expected to move little, if any, but the warm front is expected to shift a little further south later this morning into this evening. Showers and thunderstorms will be best focused right along and just north of this frontal boundary, and will traverse off to the southeast after forming in the eastern Dakotas, northern Iowa, or southern Minnesota later today. Southerly winds will feed into the front and provide the fuel for the thunderstorms, but are not expected to be very strong or most favorable for insect migration. Nonetheless, a high end Low risk of insect migration is forecast mainly between I-90 and US 136 east of US 83 to the Mississippi River, then southeast into Illinois and western Indiana along the expected path of the thunderstorm clusters that are expected to form later today. Very Low risks surround the Low risk area to account for southerly winds but more isolated or scattered precipitation coverage that may act to limit the insect drop zones in these areas. No risk of insect migration is forecast across the far northern Plains, upper Midwest, or Ontario.
Day 2 (Friday 6/22/2007 noon to Saturday 6/23/2007 noon): Relative Risk of Insect migration into the Midwest: LOW (10-15%): Greatest risk area is between I-70 and US 20 to the east of US 81 but west of I-69/65, including far eastern Nebraska, northern Kansas, much of Iowa, northern Missouri, northern and central Illinois, and western Indiana.
Click Here For The Day 2 Risk Map (opens a new window)
During the Day 2 period, the frontal boundary is expected to continue to shift to the south a little more as a result of the thunderstorm clusters acting to move the frontal boundary further south. Thunderstorms may be ongoing across especially the eastern areas of the Day 1 Low risk areas in Illinois and Indiana at the start of the period, with redevelopment expected later in the day during peak heating especially in far eastern Nebraska or Iowa and northern Missouri. Where exactly the most focused precipitation is located and where southerly winds begin to diverge due to the influence of thunderstorms (best insect drop zone areas) is just not possible in a very specific area even just a day out, but it appears right along the I-80 corridor in Iowa is a favored area as we see it now. The thunderstorms will move southeast as in previous days, so the insect migration risk is placed between US 20 and I-70 east of US 81 to I-69 and I-65 in Indiana. We will have an update in tomorrow’s outlook to determine if the risk area needs to be shifted based on what happens later today and tonight. No risk of insect migration is forecast across the upper Midwest or Ontario.
Long-term (Day 3 to Day 5: Saturday through Tuesday):
Days 3-5 (Saturday 6/23/2007 noon to Tuesday 6/26/2007 noon): Relative Risk of Insect migration into the Midwest: Day 3: LOW (5-10%): Greatest risk area is west of US 81 including western Kansas, western Nebraska, and western South and North Dakota. A secondary area also exists to the east of US 71 but west of I-75, and south of US 24, including much of Missouri, central and southern Illinois, much of Indiana, western Kentucky, and far southwestern Ohio. Days 4 and 5: LOW (10-15%): Greatest risk area on Day 4 is west of I-35 including the Dakotas, Nebraska, Kansas, western Minnesota, western Iowa, and northwestern Missouri. The greatest risk area on Day 5 is primarily west of I-39 or US 51, including the Dakotas, Nebraska, Kansas, Minnesota, western Wisconsin, Iowa, western Illinois, and Missouri.
Click Here For The Days 3-5 Risk Map (opens a new window)
The theme through this forecasting period will be the persistent area of low pressure expected to remain over the northern Plains states in the vicinity of eastern Montana, northeast Wyoming, or the western Dakotas. This weather setup allows southerly winds to be rather persistent for a longer duration of time, so migration of insects is possible from source regions not only locally but also far to the south in the south and mid-south regions of the United States.
On Day 3, redevelopment of thunderstorms is possible yet again further south along a decaying warm front across Missouri, Illinois, Indiana, southwest Ohio, and western Kentucky. Some of these areas are currently in insect source regions (especially CEW over southeast Missouri and southwest Illinois), so local migration on even weak southerly winds will be possible into this area. Despite a gradual weakening and coverage of thunderstorms in this area, the close proximity to source regions warrants a Low risk of insect migration across this area. A secondary area of insect migration risk exists west of US 81 in the western Plains as southerly winds are expected to increase in strength across this area. The coverage and amount of precipitation and subsequent more widespread insect drop zones is not expected to be really overwhelming, so just a lower end Low risk of insect migration is forecast at this time.
By Days 4 and 5, the warm front that is likely to produce heavy rainfall across the Midwest during the next 24-48 hours is expected to decrease or shift off to the north as heat and humidity build into the Midwest and Plains states on ever-increasing southerly winds. Precipitation during this time period is expected to be focused closer to the low pressure area or warm frontal boundary, especially north of I-94 and west of the Great Lakes. Southerly winds will continue to increase in speed and expand to the east, so despite a lack of precipitation across areas further south of the front, the speed of southerly winds will likely transport migratory insects further north from infested source regions further south due to the duration of time that southerly winds are expected, so a rather broad area of Low risk is forecast. On Day 4, the risk is west of I-35, and on Day 5 is west of US 51 or I-39 but east of US 83 as the low pressure and front may move far enough east to limit the risk across the far western Dakotas and the Nebraska panhandle.
Numerous insects have moved north on southerly winds over the past couple weeks, so if additional insects are currently active across the southern or mid-south states, or even further north into the Corn Belt, they will have the opportunity to move even further north into the Dakotas, Nebraska, Minnesota, and Wisconsin later this weekend and into early next week. We encourage much of the Midwest and Plains states to closely monitor insect trends (not just for CEW but other migratory insects as well) over the next week or so. Risks further east are not as high, but some migration especially on a local or regional basis is possible.
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Mike Sandstrom and Dave Changnon
Department of Geography
Northern Illinois University
DeKalb, IL 60115
E-mail: wxtrw44@yahoo.com and dchangnon@niu.edu
Temporary IMRF website: http://www.maplecity.com/~sand/cew/imrf.html
DISCLAIMER: The content in this document, and any associated figures, is strictly the opinion of the authors, and should be used for informational purposes only. The authors
assume no liability to those who may use the above content for IPM or other processes.
NOTE: This forecast, while initially developed specifically for migration of corn earworm (CEW), is applicable for all other migratory insects in the Midwest as well, such as the potato leafhopper and armyworm.
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