|HydroClim Minnesota - February 2002
A monthly electronic newsletter summarizing Minnesota climate conditions and the
resulting impact on water resources.
Distributed on the Wednesday following the first Monday of each month.
State Climatology Office - DNR Waters
WHAT HAS HAPPENED
- January precipitation was very light across
Minnesota. Precipitation totals were near or below one quarter of an inch
for all but southeastern Minnesota. Most southeastern Minnesota
communities reported precipitation totals of around two thirds of an inch.
Precipitation fell short of the historical norm by approximately one half
inch over most of Minnesota.
- keeping with a pattern established in November, temperatures in January
finished 9 to 14 degrees above the historical mean across the state. Many
Minnesota communities set all-time maximum temperature records on January
8, January 9, and January 25. Some communities in south central and
southwestern Minnesota reported temperatures in the mid to upper 50's on
January 8. The temperature at the Twin Cities International Airport fell
below zero for the first time this winter on January 18. This set a record
for the longest stretch into winter without a below-zero temperature.
According to preliminary statistics from the Midwestern Regional Climate
Center, the November through January period was the warmest such period
for the State of Minnesota by more than two degrees.
WHERE WE STAND NOW
- snow depths are less than four inches across the
southern two thirds of the state, as well as far northwestern Minnesota.
Snow cover left by last week's winter storm affecting south central and
southeastern Minnesota will erode due to this week's seasonally mild
weather. Snow cover in north central and northeastern Minnesota is
variable, ranging from three to ten inches. Many locations adjacent to the
north shore of Lake Superior report snow depths of less than three inches.
The January 31 snow depth ranking map shows that values over nearly all of
Minnesota ranked below the 20th percentile for the date. Snow depths
across large regions of the state were below the fifth percentile, and a
significant number of Minnesota communities were at the first percentile.
For an area ranking in the first percentile, it means that snow depths
were at or below the all-time minimum value for the date.
- heavy late November rainfall and snowfall brought relief to areas
affected by precipitation deficits established during the later part of
the 2001 growing season. Because the considerable November precipitation
fell before soil freeze-up, the soil moisture profile was amply recharged
in most areas. There are reports from western Minnesota of dry soil near
the surface due to the limited winter snowfall.
- as of January 29, the National Drought Mitigation Center designates most
of the southeastern one quarter of Minnesota and portions of northwestern
Minnesota as "Abnormally Dry". The remainder of the state is
free of any drought designation. The NDMC index is a blend of science and
subjectivity where intensity categories are based on six key indicators
and numerous supplementary indicators.
- the February 2 Palmer Drought Severity Index (PDSI) from the Climate
Prediction Center places south central, central, and east central
Minnesota counties in the "Moderate Drought" category. Other
areas are categorized as "Near Normal". The Palmer Drought
Severity Index is used for assessing long-term meteorological conditions.
- the U.S. Geological Survey indicates that discharge values for all
Minnesota streams (where winter reporting is possible) are in the normal
to above normal categories for the date.
- soil frost depth data gathered on January 29 by the U.S. Army Corps of
Engineers and the University of Minnesota indicate that frost depths, as
measured under a sod surface, were 4 to 10 inches in the south, 12 to 18
inches in the west and north. Soil frost penetration depths would
typically be twice that of this year's levels.
- the February precipitation outlook from the
Climate Prediction Center shows no significant tendencies away from
climatological probabilities. Historically, February is Minnesota's driest
month with precipitation normals ranging from less than one half inch in
northwestern Minnesota to near three quarters of an inch in eastern
sections of the state. The median snow cover at the end of February ranges
from under 5 inches in the southwest Minnesota, to over 18 inches on the
ground in northeastern Minnesota (greater than 30 inches in the Lake
Superior highlands). The February temperature outlook also shows no
significant tendencies away from climatological probabilities. Normal
February high temperatures climb from the mid to upper teens early in the
month to the mid to upper 20's by month's end. Normal February lows begin
the month from near minus 10 degrees in the far north, the single digits
above zero in southern Minnesota. By late February, normal lows are in the
low single digits above zero in the far north, and near 10 degrees in the
- the 90-day precipitation outlook for February through April shows no
significant tendencies away from climatological probabilities. The
February though April temperature outlook also shows no significant
tendencies away from climatological probabilities.
- the National Weather Service produces long-range probabilistic river
stage and discharge outlooks for the Red River, Minnesota River, and upper
Mississippi River basins. A hydrologic model is initialized using the
current conditions of stream flow and soil moisture across a basin. The
model is allowed to run into the future with multiple scenarios using more
than 30 years of climatological data. The climatological data are weighted
by the 90 day outlooks for temperature and precipitation trends. The model
output offers a complete range of probabilistic values of stream stage and
discharge for numerous forecast points. The product offers a risk
assessment tool which can be used in long-range planning decisions
involving flooding or low-flow concerns. These products are part of the
National Weather Service's Advanced Hydrologic Prediction Service (AHPS)
and will be produced near the middle of each month.
FROM THE AUTHOR
- staff from various state and federal agencies
gathered at this year's annual interagency spring flood coordination
meeting on January 29. To state the obvious, spring flood potential was
declared be quite low at this time. It was interesting to note that this
meeting was very well attended in spite of the lack of pressing flooding
concerns. Minnesota's water resource professionals recognize the need for
interagency communication and cooperation when dealing with flood
situations. These individuals utilize opportunities such the annual
meeting to build relationships, and to share concerns and ideas. We
Minnesotans are most fortunate to have them overseeing the protection of
lives and property against the threat of flooding. In keeping with that
theme ... it was announced at this year's meeting that Gary McDevitt,
hydrologist at the National Weather Service Forecast Office in Chanhassen,
has recently won the prestigious "Isaac M. Cline" national award
for hydrology. Gary was recognized for his outstanding service to the
citizens of Minnesota during the 2001 spring flood episode.
- in the discussions above, I point out that two of the national drought
monitoring indices depict portions of Minnesota in developing or ongoing
drought categories. The indices reflect the scarcity of winter snowfall
and the extraordinarily warm winter temperatures, and attempt to quantify
the present climatological anomaly. Precipitation deficits that occur
during the Minnesota winter have a profound affect on the winter
recreation industry. However, from a water resource standpoint we must
recall that on average, the total water volume deposited by winter
precipitation is small when compared to annual precipitation. Therefore,
below normal winter precipitation has a much smaller impact on water
resources than deficits established during the growing season.
NOTES FROM AROUND THE STATE
- beginning this spring, the National Weather
Service will issue probabilistic river stage and discharge outlooks for
the Mississippi River above Red Wing. Previously, probabilistic outlooks
were available only for the Minnesota and Red River basins.
UPCOMING DATES OF NOTE
- February 14, Climate Prediction Center releases
30/90 day temperature and precipitation outlooks
- February 14-21, Probabilistic Flood Outlooks issued by National Weather
- February 20, Interagency Flood Planning Coordination Meeting - National
Weather Service, Chanhassen
- February 22, Narrative Flood Outlook issued by National Weather Service
WEB SITES FEATURED IN THIS EDITION
http://climate.umn.edu - Minnesota Climatology Working Group
http://enso.unl.edu/ndmc/ - National Drought Mitigation Center
http://www.cpc.ncep.noaa.gov - Climate Prediction Center
- U.S. Geological Survey, Minnesota
- U.S. Army Corps of Engineers, St. Paul District
http://www.crh.noaa.gov/ahps/index.html - National Weather Service - Central Region Headquarters
- Dan Luna, Hydrologist in Charge, National Weather
Service - North Central River Forecast Center
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