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: Wednesday, June 13, 2007, 11AM central time
Short-term (present to 48 hours):
Day 1 (Wednesday 6/13/2007 noon to Thursday 6/14/2007 noon): Relative Risk of Insect migration into the Midwest: LOW (5-10%): Greatest risk area is west of US 59 south of I-90 and east of US 83, including southern South Dakota, far southwestern Minnesota, Nebraska, far western Iowa, far northwestern Missouri, and Kansas.
Click Here For The Day 1 Risk Map (opens a new window)
The surface weather maps this morning show an elongated stationary frontal boundary across the Plains from central North Dakota southward into western Kansas and points south. Showers and thunderstorms are rather common along the entire length of the boundary, but are currently staying mostly west of I-29. Further east, high pressure continues to hold firm across the northern Great Lakes, blocking the front and associated precipitation from moving to the east. Due to the position of the high pressure, winds with an easterly component are found to the east of the Mississippi River, with southerly winds focused to the west of the Mississippi River but still with an easterly component.
From now until midday Thursday, little is expected to change to the overall weather pattern across the forecast area from previous days, with some weakening in the strength of the front and its associated precipitation. Winds will continue to be rather weak in the vicinity of the front and precipitation, with most of the activity expected to stay west of US 59 but east of US 83 as the front maybe moves a few miles or kilometers to the east. With a decrease in strength and a continuation of winds with an easterly component versus those with a predominant southerly component that we look for in terms of insect migration, only a Very Low risk of insect migration is forecast mainly south of I-90 and west of US 59, but east of US 83 closer to active insect source regions and possible scattered precipitation today into tomorrow. No risk exists to the east of I-35 due to the influence of high pressure and unfavorable migratory winds.
Day 2 (Thursday 6/14/2007 noon to Friday 6/15/2007 noon): Relative Risk of Insect migration into the Midwest: VERY LOW (2-5%): Greatest risk area is west of I-35 mainly south of US 2, including North Dakota, South Dakota, Nebraska, Kansas, western Minnesota, western Iowa, and northwestern Missouri.
Click Here For The Day 2 Risk Map (opens a new window)
The frontal system across the Plains states is expected to continue to weaken and become ill-defined, so a more focused concentration of precipitation (potential insect drop zones) will be harder to come by during the Day 2 period compared to what has been observed the past several days. The high pressure over the Great Lakes will continue its residence over that region, so wind flow will continue to be rather weak despite a low pressure area rapidly moving across far southern Canada. This low pressure area, however, will provide little to change the weather across the Plains despite maintaining weak southerly flow. A Very Low risk is forecast to the west of I-35 to account for local migration of insects and possible scattered insect drop zones where precipitation does occur, but the threat does not appear to be anything to write home about at this time.
Long-term (Day 3 to Day 5: Friday through Monday):
Days 3-5 (Friday 6/15/2007 noon to Monday 6/18/2007 noon): Relative Risk of Insect migration into the Midwest: Days 3-4: VERY LOW (2-5%) on Day 3 with LOW (5-10%) on Day 4: Greatest risk is west of I-35 and north of I-80, including the Dakotas, northern Nebraska, western Minnesota, and northwest Iowa. Day 5: LOW (10-15%): Greatest risk area is mainly south of US 2 between US 83 and a line from Ironwood, Michigan to Des Moines to Wichita.
Click Here For The Days 3-5 Risk Map (opens a new window)
The quick-moving low pressure is expected to continue to move east across southern Canada, keeping the chance of scattered precipitation and southerly winds across the Plains states on Day 3, so a Very Low risk to account for any localized insect drop zones is forecast mainly west of I-35 and north of I-80 in closer proximity to the low and where precipitation is likely to be more focused where it does occur. The high pressure that has meandered across the Great Lakes states for the past several days, however, will finally begin to move to the east in response to a stronger developing low pressure center over the northern Rockies by the end of the Day 3 period. The high pressure will continue to control the weather over the eastern forecast area, however, so no risk of insect migration is forecast to the east of I-35 on Day 3.
By Days 4 and 5, a more potent low pressure area is expected to move from the northern Rockies into the Plains and upper Midwest, bringing a return of respectable southerly flow and the next chance of more widespread precipitation to especially the western forecast area through Day 5. On Day 4, the low pressure area is expected to be in eastern Wyoming or Montana, with a developing warm front between the I-90 and I-94 corridors east to I-35. Some precipitation is expected to develop near this boundary, and with southerly winds making a return to the Plains, a Low risk of insect migration is warranted mainly north of I-80 to the west of I-35 where precipitation is expected to be best focused. No risk of insect migration is forecast to continue across the eastern Midwest to the east of the Mississippi River as high pressure continues to move to the east. On Day 5, the low pressure and attendant frontal systems continues to deepen and move to the east, increasing southerly winds across a larger part of the Plains and Midwest in addition to increasing precipitation coverage (insect drop zones). The system is not expected to be as strong as the last major system that passed through the area approximately a week ago, but will likely still be a potential insect mover given good southerly flow and precipitation mainly west of the Mississippi River through Day 5. A high-end Low risk of insect migration is forecast from Sunday into Monday between US 83 and roughly I-35 south of US 2.
Corn earworm counts are increasing especially across the southern areas of the forecast area (southern Missouri and southern Illinois), with significant increases noted in extreme southeast Missouri and southwestern Illinois since this past weekend. As favorable hosts continue to develop and become more attractive to CEW and other migratory insects further north, a potential increase in counts may occur in association with this system early next week so we will continue to monitor conditions and provide updates in future outlooks on areas that are at elevated risks of insect migration.
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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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