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| Special Report to iowasnowmobiler.com: 2004-05 Winter Preview (from 12/13/04) |
By Harry Hillaker, State Climatologist
Iowa Department of Agriculture & Land Stewardship
There certainly has not been much snow so far in Iowa. The statewide
average snowfall has been only about an inch through mid-December
with no single location having more than about 2.5 inches on the ground
at any one time.
There is not much to go on for making an outlook. We are experiencing
a fairly weak El Nino event at the moment and a weak to moderate El
Nino is expected to be in place for the winter season.
El Nino generally does not have a major impact upon the total amount of
snow that we see in Iowa; however, the distribution of that snow within
the season, as well as our mid-winter temperatures, usually is different.
Typically, we see more snow during the fringes of the winter season
when El Nino is around. Thus, snow amounts in late October to early
December and from late February to late April are frequently greater
than usual while temperatures during that time are usually a little cooler
than normal. The mid-winter season (mid-December to mid-February)
is usually much warmer than usual while snowfall averages a little less
than usual.
The overall result of this typical sequence of events is that whatever
snow we get does not stick around as long as usual. The bulk of snow
comes in the fringes of the season when temperatures usually are
marginal for maintaining a snow pack. Meanwhile, the mid-season
brings less than the usual amount of snow and also contains more mild
periods than usual, thus limiting the persistence of whatever snow
should fall.
This year, we seem to have jumped straight into the mid-winter El Nino
pattern of milder temperatures and less precipitation and did not see the
colder/wetter pattern we have seen in many other El Nino falls (1991
and 1997, for example).
There is plenty of very cold air present in the Arctic right now.
However, this very cold air is not currently located in an area where it is
likely to quickly come in to our part of the U.S. (i.e., the cold is in
northeast Canada and all across Siberia; things are pretty mild in the
region ‘upwind’ of Iowa in Alaska and the Yukon). This pattern has
been very persistent.
Finally, ‘weak’ El Ninos, such as our current one, are much poorer
predictors than strong El Ninos. Thus, just as this past autumn outlook
was a ‘bust’, the odds that the upcoming season outlook will not verify
is higher than usual.
Iowa Department of Agriculture & Land Stewardship
There certainly has not been much snow so far in Iowa. The statewide
average snowfall has been only about an inch through mid-December
with no single location having more than about 2.5 inches on the ground
at any one time.
There is not much to go on for making an outlook. We are experiencing
a fairly weak El Nino event at the moment and a weak to moderate El
Nino is expected to be in place for the winter season.
El Nino generally does not have a major impact upon the total amount of
snow that we see in Iowa; however, the distribution of that snow within
the season, as well as our mid-winter temperatures, usually is different.
Typically, we see more snow during the fringes of the winter season
when El Nino is around. Thus, snow amounts in late October to early
December and from late February to late April are frequently greater
than usual while temperatures during that time are usually a little cooler
than normal. The mid-winter season (mid-December to mid-February)
is usually much warmer than usual while snowfall averages a little less
than usual.
The overall result of this typical sequence of events is that whatever
snow we get does not stick around as long as usual. The bulk of snow
comes in the fringes of the season when temperatures usually are
marginal for maintaining a snow pack. Meanwhile, the mid-season
brings less than the usual amount of snow and also contains more mild
periods than usual, thus limiting the persistence of whatever snow
should fall.
This year, we seem to have jumped straight into the mid-winter El Nino
pattern of milder temperatures and less precipitation and did not see the
colder/wetter pattern we have seen in many other El Nino falls (1991
and 1997, for example).
There is plenty of very cold air present in the Arctic right now.
However, this very cold air is not currently located in an area where it is
likely to quickly come in to our part of the U.S. (i.e., the cold is in
northeast Canada and all across Siberia; things are pretty mild in the
region ‘upwind’ of Iowa in Alaska and the Yukon). This pattern has
been very persistent.
Finally, ‘weak’ El Ninos, such as our current one, are much poorer
predictors than strong El Ninos. Thus, just as this past autumn outlook
was a ‘bust’, the odds that the upcoming season outlook will not verify
is higher than usual.