Indiana fall weather absent a 'dominant driver' this year

October 1, 2013  

WEST LAFAYETTE, Ind. - The lack of a developing, dominant weather system coupled with erratic changes over the past year indicate that Indiana could be in for wide swings in weather in the early weeks of autumn, the State Climate Office says. 

The October outlook is for above-normal temperatures with equal chances for above- normal, normal and below-normal precipitation. Weather beyond October is more difficult to assess because climatological systems such as El Niño and La Niña that would drive Indiana weather into November are still evolving.

"This is a time when we should be cautious about looking too far into the future, especially when we don't have a dominant driver," said Dev Niyogi, state climatologist based at Purdue University. "There are some years when we have very strong indicators. When El Niño and La Niña are active, they tend to dictate the weather of our upcoming season, and we can project with higher confidence whether it will be warmer or drier."

The fall season will be influenced by multiple air masses, any of which could dominate at any time, Niyogi said.

"If we have a tropical atmosphere becoming more active, then we can expect more warmer and humid weather conditions, with more storm activity," he said. "On the other hand, if that is not the dominant factor, then we might have the potential for a colder, drier air mass coming to Indiana more frequently."

Which pattern might develop as the stronger of the two is in question at this time.

"And therein lies our dilemma at this point in drawing one strong, singular conclusion as to what will dominate," he said. "But one thing that we can say for certain is in the absence of one strong driver and that we will be influenced by multiple air masses, it is very likely that Indiana will witness wide swings in its week-by-week weather as we go into the new season."

Adding to the difficulty in forecasting is the unusual weather Indiana has experienced in the past couple of years, especially since last year when drought was so severe that it led to fire and watering bans and drastically lowered crop yields. Indiana emerged from drought over the winter with frequent precipitation, which was followed by an abundance of spring rain that delayed many farmers in planting their crops.

Then, in another turnabout, Indiana this summer again fell into an extended dry period that brought back drought to some areas and lowered high expectations for excellent crop yields.

The U.S. Drought Monitor update of Sept. 26 showed that heavy rains the previous week brought some relief to Indiana. Several counties in the state's midsection that had been in moderate drought - the lowest level of drought - improved to abnormally dry. Some other counties got enough rain to eliminate dry conditions.

Niyogi said the climate office will continue to monitor the situation to determine whether any particular weather driver seems to become dominant. The office will provide an updated outlook later in the fall.

Ken Scheeringa, associate state climatologist, said autumn typically is a difficult time for forecasting because the state is transitioning from the summer to weather patterns that will establish themselves for the winter.

"Sometimes there is a very sharp cutoff between seasons, but that's not happening," he said.

One thing about the fall that Scheeringa could say with absolute certainty - and with tongue in cheek: "Autumn arrived at 4:44 p.m. EDT on Sept. 22 - exactly as predicted well in advance."  

Writer: Keith Robinson, 765-494-2722,  

Sources: Dev Niyogi, 765-494-6574, 

Ken Scheeringa, 765-494-8105, 

Related website:
Indiana State Climate Office

Ag Communications: (765) 494-2722;
Keith Robinson,
Agriculture News Page

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