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GREAT LAKES FREEZE-UP OUTLOOK
NATIONAL WEATHER SERVICE CLEVELAND OH
1256 PM EST Wed Nov 06 2024


...Great Lakes Ice Season for 2024-2025 Expected to Be Below
Average Ice Cover...

But...not as low as the anomalous 2023-2024 season.

In a summary preface, a weak La Nina is expected into the winter
months, temperatures have been above normal on the whole over the
past few weeks and will continue into the next couple of weeks, and
surface water temperatures across all Great Lakes are also running
above normal for this time of year. Ice development may be delayed
and the forecast for the season is below normal ice coverage for
2024-2025. The details follow.


As we head deeper into the the Fall season, we are in the midst of
the transition from the strong El Nino experienced in the winter of
2023-2024 into La Nina, but currently are at neutral conditions.
Long range forecasts are predicting this La Nina to be on the weaker
side and persisting through the winter.

It is important to note that the status of El Nino/La Nina is not
the sole determining factor in the long range winter outlooks, but
it does set many things into motion. It will have influence on the
other teleconnections such as the Arctic Oscillation (AO), the
Pacific/North American teleconnection (PNA), and the North Atlantic
Oscillation (NAO), and the influences are not always the same
despite similar statuses of El Nino/La Nina of past years. These
teleconnections will often times have more of a direct impact on the
seasonal conditions for the Great Lakes region. They will respond to
the El Nino/La Nina occurring at the time and can then affect the
local surface and upper level patterns over the Great Lakes for
significant periods of time, ultimately influencing the behavior of
the Great Lakes water temperatures and potential for freezing.

Over the next two weeks, none of the teleconnections are showing any
strong signals either way, although the AO and the NAO will be
slightly positive. This can translate to milder conditions compared
to early/mid November normals over the Great Lakes.

The Oceanic Nino Index is a measure of the relative strengths of El
Nino/La Nina over a three month period at a specific portion of the
equatorial Pacific Ocean. There were 4 winter seasons since records
have been kept where a weak La Nina emerged in the Oceanic Nino
Index after an early Fall transition period like we are in now, and
after a strong El Nino the previous winter that was characteristic
of below average ice cover. These winters that followed were also
characteristic of below average ice cover for the Great Lakes on the
whole in 3 of the 4 similar events.

Looking back over the past month, October has run 1-3 degrees
Fahrenheit above normal for the southern portion of the Great Lakes,
and 3-6 degrees Fahrenheit above normal for the central and northern
portions of the Great Lakes. Long range model ensemble forecasts
over the next two weeks depicts the overall potential for milder
than normal conditions continuing through the middle of
November. There is good consensus for this to occur amongst the
different long range forecast model ensembles.

Along with the warmer than normal conditions overall for the month
of October, water temperatures across all of the Great Lakes are
entering the cold season significantly above normal as well. With
data compiled from 1995 onward, surface water temperature averages
are running around 2-3 degrees Fahrenheit above normal for early
November. Given these sets of information, the start of the ice
season could be delayed unless some significant weather pattern
changes that bring about more persistent cold airmasses into the
Great Lakes occur for the end of November and into December.

Something to watch during the winter is the potential for a more
active larger scale pattern for the Great Lakes with higher amounts
of precipitation, but also perhaps with weather systems producing
higher amplitude swings of temperature. It is important to note that
a long range prediction of slightly milder than normal temperatures
for the region can still include cold air outbreaks, but with the
net average still being above normal over an extended period of
time. One component of this we will watch is the stratospheric polar
vortex. If it weakens, this allows colder airmasses to drop
southward from the polar regions more easily as opposed to when the
vortex is strong where it becomes more difficult for the colder
airmasses to migrate southward, which was the case last season. But
in the end, these may be only short lived features that exit and
then rebound to mild winter temperatures once again.


Keep in mind that ice could develop earlier or later since ice
development is highly dependent on the occurrence of cold air
outbreaks and warm periods across the Great Lakes during the next
two months.

Ice formation is determined by two factors: The amount of heat
stored in the water from the summer and how fast that heat can be
removed by arctic outbreaks of Polar/Arctic air and high winds. Long
range outlooks do not consider the "storminess" factor which can
significantly alter the thermal structure of the lakes over short
periods of time.



THE LATEST HARBOR WATER TEMPERATURES COMPARED TO PREVIOUS YEARS:

                 2024 2023 2022 2021 2020 2019 2018 2017 2016 NORMAL

DULUTH            49   49   51   44   40   40   42   44   48    44
SAULT STE MARIE   54   47   51   48   48   46   42   44   50    47
CHICAGO           56   53   55   52   47   44   46   44   52    53
ALPENA            51   51   54   49   47   42   42   46   50    48
DETROIT           56   49   51   47   52   44   43   42   50    52
CLEVELAND         59   53   55   53   53   51   48   50   55    56
BUFFALO           57   55   56   53   50   52   49   46   50    54

WATER TEMPERATURES FROM THE MID-LAKE BUOYS OR NEARBY SHIPS COMPARED
TO PREVIOUS YEARS:

LAKE SUPERIOR
WEST              47   43   45   48   45   44   44   52   49    47
CENTRAL           48   44   44   MM   41   43   41   52   47    47
EAST              49   45   45   MM   42   46   41   52   52    48

LAKE MICHIGAN
NORTH             53   52   48   56   50   51   49   56   59    54
SOUTH             57   54   51   59   47   50   51   58   61    56

LAKE HURON
NORTH             48   46   51   57   49   49   45   51   56    53
SOUTH             58   53   54   56   46   49   49   59   57    55

LAKE ERIE
WEST              56   54   54   60   MM   53   53   56   61    56
CENTRAL           59   55   57   60   55   56   53   63   62    58
EAST              58   55   56   60   53   54   53   62   59    57


FREEZING DEGREE DAY ACCUMULATIONS AT SELECTED STATIONS
COMPARED TO NORMAL CALCULATED ON Tue Nov 5:

LOCATION           DATE   NORMAL CURRENT
----------------------------------------

   DULUTH,   MN  NOV    4    0    0
MARQUETTE,   MI  NOV    4    0    0
SAU_S_MAR,   MI  NOV    4    0    0
 GREENBAY,   WI  NOV    4    0    0
MILWAUKEE,   WI  NOV    4    0    0
  CHICAGO,   IL  NOV    4    0    0
 MUSKEGON,   MI  NOV    4    0    0
   ALPENA,   MI  NOV    4    0    0
  DETROIT,   MI  NOV    4    0    0
   TOLEDO,   OH  NOV    4    0    0
CLEVELAND,   OH  NOV    4    0    0
  BUFFALO,   NY  NOV    4    0    0


NORMAL TEMPS FOR SELECTED LOCATIONS AROUND THE
GREAT LAKES FOR Tue Nov 5

LOCATION     HIGH LOW
----------------------------------------------

    DULUTH,MN  38  24
 MARQUETTE,MI  39  27
  GREENBAY,WI  45  28
 MILWAUKEE,WI  48  34
   CHICAGO,IL  50  33
  MUSKEGON,MI  48  33
    ALPENA,MI  45  29
   DETROIT,MI  50  35
    TOLEDO,OH  50  34
 CLEVELAND,OH  51  37
   BUFFALO,NY  49  36


THE NEXT FREEZE-UP OUTLOOK WILL BE ISSUED IN APPROXIMATELY TWO WEEKS.


$$

Marsalek