Warm, dry conditions ahead

After another wet weekend and cooler temperatures to start this week, it may be surprising to hear that conditions will be changing back to warm and dry for the next several weeks.  Climate models are strongly favoring above-normal temperature throughout the rest of September with a slight favoring of below-normal precipitation.  Abnormally dry conditions continue to persist in counties across northern Indiana, but the spatial extent is gradually shrinking  (Figure 1).  It is too soon to tell if the upcoming warm and dry outlooks will be strong enough to expand and intensify those drier areas or if a few periodic rain events will be enough to keep conditions relatively stable.  Monthly (October) and seasonal (September-October-November) outlooks were released on 15 September 2022.  For both of these time frames, the outlooks are favoring above-normal temperatures to continue with below-normal precipitation across Indiana (Figure 2).

With each day that passes, we get closer to the first fall freeze event – whether that is defined at 32°F, 28°F, or some other temperature threshold.  Over the past several decades, with increasing temperatures, the story has been an expanding growing season defined as the consecutive number of days between the last spring freeze and first fall freeze.  Is this expanded season highly variable from year to year or relatively stable?  If the growing season, on average, is expanding, is it due more to earlier last spring freeze dates or later first fall freeze dates?  The Midwestern Regional Climate Center (mrcc.purdue.edu) has developed a new tool that allows users to peruse the historical data and find answers to these questions and more.  This tool will be formally launched later this fall, but a webinar is being offered this next Wednesday, September 21, 2022 at 11am EDT (https://www.zoomgov.com/j/1605071265) for anyone wanting sneak peek and learn more about what the findings say.  This is a project that was supported by the USDA Midwest Climate Hub with a focus on agricultural impacts and awareness regarding climate trends and extremes.

Finally, as temperatures gradually cool, the accumulation rate of modified growing degree days (MGDD) slows down.  Figures 3 and 4 show the latest accumulation totals and departure from climatological average, respectively. MGDDs now range from slightly over 3400 units in southern Indiana to around 2000 units in the northern counties.  These accumulations are around 150-200 units above normal across central and southern parts of the state and near normal in the northern third counties.

drought monitor

Figure 1. U.S. Drought Monitor for data through August 30, 2022.

climate outlook

Figure 2. Climate outlook for the 3-month period of September-October-November from the national Climate Prediction Center. Levels of shading indicate levels of confidence for above- or below-normal conditions to occur. Temperature outlook is on the left; Precipitation outlook is on the right.

growing degrees

Figure 3. Modified growing degree day (50°F / 86°F) accumulation from April 15-September 13, 2022.

growing degrees

Figure 4. Modified growing degree day (50°F / 86°F) accumulation from April 15-September 13, 2022, represented as the departure from the 1991-2020 climatological average.

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