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: Tuesday, July 17, 2007, Noon central time
Short-term (present to 48 hours):
Day 1 (Tuesday 7/17/2007 noon to Wednesday 7/18/2007 noon): Relative Risk of Insect migration into the Midwest: LOW (10-15%): Greatest risk is east of US 81, south of I-94, north of US 136 west of the Mississippi River and north of a line from Quincy, Illinois to Paducah east of the Mississippi River, and west of I-75, including eastern South Dakota, eastern Nebraska, southern Minnesota, Iowa, northern Missouri, northern and central Illinois, extreme southern Wisconsin, extreme southern Michigan, Indiana, western Ohio, and northwestern Kentucky.
Click Here For The Day 1 Risk Map (opens a new window)
The surface weather map this morning shows a low pressure center over central Montana with a weaker low pressure in southeastern South Dakota. A stationary front stretches from the central Montana low to the South Dakota low, then southeast through Des Moines, Quincy (Illinois), Evansville, and Lexington, Kentucky. Numerous clusters of showers and thunderstorms are found along and just north of the front from eastern Iowa into Illinois and Indiana. Wind flow north of the front is from the east or southeast, while immediately south of the front, winds quickly shift to the south or southwest and cover much of the southern Midwest and mid-south in active insect source regions.
During the next 24 hours, what you see is what you get. The frontal boundary is expected to move little over the next 24 to 36 hours, so areas that have experienced rainfall in the past 12 hours or so will likely see additional rainfall and also possible insect drop out. The current areas of showers and thunderstorms will likely dissipate somewhat throughout this afternoon before regeneration occurs over Iowa and southern Minnesota as southerly winds feed into and over the frontal boundary to the south. The showers and thunderstorms will then spread southeast along the frontal boundary into Illinois and Indiana. Southerly wind flow into the frontal boundary is not particularly strong due to a lack of a good high pressure over the eastern United States, so we are only going to keep the insect migration risk in the higher end Low category across the Corn Belt, with a Very Low risk surrounding the Low risk area, especially to the south. No risk of insect migration is forecast across the far northern Midwest and northwestern Plains, along with the majority of the upper Great Lakes region and Ontario.
Day 2 (Wednesday 7/18/2007 noon to Thursday 7/19/2007 noon): Relative Risk of Insect migration into the Midwest: LOW (5-10%): Greatest risk area is east of US 83, south of I-90, and north of I-70, including eastern Nebraska, extreme southern South Dakota, northern Kansas, northern Missouri, Iowa, extreme southern Minnesota, northern and central Illinois, Indiana, and Ohio.
Click Here For The Day 2 Risk Map (opens a new window)
The only change from Day 1 to Day 2 is a possible slight southern movement to the frontal boundary, so to account for this the risk area is dropped further to the south to near I-70. Low pressure is expected to remain over the Plains states, but with high pressure dropping south from Canada, the low pressure and attendant frontal boundary will likely be nudged a little further south. This will place the front a little closer to active insect source regions in the mid-south and extreme southern Midwest, but southerly winds south of the front are expected to decrease in speed a little bit, so a Low risk of insect migration is maintained in the forecast basically across the same area but a touch south compared to Day 1. High pressure will bring no risk of insect migration into the upper Midwest, most of the upper Great Lakes states and Ontario, and also across the northwestern Plains. It is also important to note that the strength of shower and thunderstorm clusters will also dictate where the front sets up, so we will monitor conditions later today and tonight and provide an update in the forecast tomorrow morning.
Long-term (Day 3 to Day 5: Thursday through Sunday):
Days 3-5 (Thursday 7/19/2007 noon to Sunday 7/22/2007 noon): Relative Risk of Insect migration into the Midwest: Day 3: LOW (5-10%): Greatest risk area is south of I-72 and US 36, mainly east of US 81, including eastern Kansas, Missouri, central and southern Illinois, Indiana, Ohio, and Kentucky. Day 4: VERY LOW (2-5%): Greatest risk area is south of I-44 and I-70, including southern Missouri, southern Illinois, Kentucky, southern Indiana, and southern Ohio. Day 5: VERY LOW (2-5%): Greatest risk area is west of US 81, including the Dakotas, Nebraska, and Kansas.
Click Here For The Days 3-5 Risk Map (opens a new window)
During Days 3 and 4, the low pressure system is expected to move east as the front moves to the south, due to high pressure building in across the upper Midwest. Showers and thunderstorms will continue to develop along the frontal boundary and move east or southeast, but in time will be focused more and more across the southern region of the forecast area, mainly south of I-80 and I-72 on Day 3 and then south of I-44 and I-70 by Day 4. Southerly wind flow to the south of the front is expected to continue to be rather light, however, and so the risk level on Day 3 is in the Low category but by Day 4, the risk level is dropped into the Very Low category as the best risk will actually be in or very near active insect source regions so migration is not a big factor. The front is expected to move to the south and east of the forecast region by Day 5, so no risk in association with this front is in the Day 5 period.
Attention by late in the Day 4 and Day 5 period then shifts back to the Plains as high pressure over the Great Lakes begins to drift to the east and low pressure develops over eastern Montana once again. Southerly winds are expected to return to the Plains states by late in the Day 4 period or by Day 5, so at this point a Very Low risk is justified mainly west of US 81 for the Day 5 period. No other risk area is forecast across the region for Day 5.
Corn earworm trap counts have increased at least a little bit (a few moths a night) in northeast Arkansas the past few mornings, and a continued rather stable population of CEW exists south of I-40 at this time. Over the next few weeks, we will have to monitor weather systems that could move these insects further north so please stay tuned as the second generation for the Midwest begins to come into play.
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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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