Posts
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"Stuck" Pattern Regimes Coming The Next Month
Nicholas
Humphrey
25
July, 2018
It
appears many places suffering major extremes will not catch a break
in the month of August...although a couple places may swing the
pendulum.
I
looked at long range models which consider longer averaged anomalies
compared to climatology. They use an ensemble of different model
conditions. From this, we can use these models to forecast the most
likely areas which will have highest chances for above or below
average precipitation and temperatures. It's not the same type of
forecasting as for short range (within days) because it's impossible
to reliably forecast specific temperatures and precipitation amounts
weeks in advance (atmospheric fluid chaos and rapid growth in model
errors prevent this). But the models used in the way described above
can be instead used to estimate areas where anomalies may develop
based on their tendencies and previous performance in forecasts.
Note,
there is no way for me to say how extreme the anomalies I'm
forecasting may be in the end. That is still a short-term weather
prediction situation. However, given what we've seen thus far, any
strong signals produced by the forecast pattern regimes can certainly
lead to more opportunities for extreme events (short-lived or
prolonged) as our climate continues to more abruptly shift to more
extreme conditions. So stay tuned on that front!
So
with that out of the way, let's look at some areas which are
currently under the gun for these major summertime extremes we are
witnessing, exacerbated by our planet's rapidly shifting climate.
Europe
Northern
Europe appears likely to continue to deal with below average
precipitation through the end of August. Especially Scandinavia and
Northwest Russia. Areas to the south, particularly Greece and
Southeast Europe will likely see above average precipitation. Because
of the strong signal and given recent problems with fires, any heavy
precipitation from thunderstorm activity in Greece would be capable
of producing flooding in those areas. As for Northern Europe, these
are not favorable conditions given the widespread drought, wildfires
and crop failures ongoing.
(Ensemble
total precipitation anomalies in Europe through August 23th).
Temperatures
will likely remain above to well above normal over much of Europe
through the first third of August with below normal temps in
southeast Europe. Toward the middle of the month, the heat anomalies
should become more focused on western and central Europe with
continued near or below average conditions near Greece.
(5-Day
ensemble mean temperature anomalies in the lower atmosphere through
August 9th above and August 19th below. Note the pattern signal
decreases with increasing lead time, but abnormal temperatures
appeared favored in central and western Europe going into the middle
of the month).
North
America
There
is a strong signal for above or well-above average precipitation
across portions of the US South, Mid-Atlantic, into southern New
England. These areas have already received and continue to receive
copious amounts of rain with flooding problems and that appears
likely to continue into August. There is a possibility of above
average precipitation over the High Plains into Arizona and New
Mexico as monsoon season continues. The Climate Prediction Center
does indicate some improvement in drought conditions is possible over
that region. However, near normal rainfall on the Southern Plains and
the Pacific Northwest is not enough given previous weeks to months of
dryness and drought conditions may actually worsen in those areas
over the next month into Autumn.
Although
not a particularly strong signal, there is some risk of above normal
precipitation in Quebec with below normal precipitation in parts of
western and northwestern Canada. Given the abnormal dryness in the
West, this would mean increasing drought conditions possible.
(Ensemble
total precipitation anomalies in North America through August 23th).
(Seasonal
Drought Outlook by the US Climate Prediction Center. Widespread
drought likely over the Southern Plains and Midwest into parts of the
South. Will continue over the Southwest US even with the improvement
possible, with expansion over the Pacific Northwest).
(North
American Drought Monitor showing abnormally dry conditions over much
of British Columbia extending into the Prairies as of June 30th).
Overall
Western North America and New England appear to be the most favorable
areas for above normal temperatures going into much of August. Alaska
will also likely see above to well-above average temperatures.
Meanwhile, much of the center of North America (Canada and US) will
likely see below average temperatures. As the month progresses, the
focus of heat anomalies is expected to be more over the US Pacific
Northwest/Southern BC, with continued favored heat over the Northeast
US and eastern Canada. A signal for below normal temperatures is
possible over the Desert Southwest as monsoon activity intensifies.
(5-Day
ensemble mean temperature anomalies in the lower atmosphere through
July 31st above and August 19th below. Note the pattern signal
decreases with increasing lead time, but abnormal temperatures
appeared favored in the US Pacific Northwest and the Northeast as
well as Quebec going into the middle of the month).
Asia
It
looks like the heat anomalies over much of Japan will decrease going
into August, although there will be more persistent heat over Eastern
China and the Korean Peninsula through the earlier days of August.
Temperatures look to be much below normal over much of Siberia in
response to the persistent extreme heat in Europe. Through the middle
of month, some abnormal warmth may continue over northeast China.
Also note, throughout the month Iran has a persistent signal for
above normal temperatures. Drought and heat waves are ongoing there
right now.
(5-Day
ensemble mean temperature anomalies in the lower atmosphere through
August 4th above and August 19th below. Note the pattern signal
decreases with increasing lead time, but abnormal temperatures
appeared favored in the Iran and Northeast China going through the
middle of the month).
As
for precipitation, a much below normal precipitation regime is likely
over northeast China, much of mainland Japan and particularly over
the Korean Peninsula where it has been hot and dry recently. The
dryness appears to intensify through much of August. Significant
negative anomalies are present over parts of India as well.
Meanwhile, above average precipitation is likely over Southeast Asia
and the Philippines, some of which is likely to be related to
tropical cyclone activity. A growing El Nino regime developing in the
Tropical Pacific favors a more active monsoon trough (where
converging winds caused localized lift and widespread thunderstorm
activity can develop low pressure areas and cyclones, if favorable).
Vietnam has been dealing with extensive heavy rain and flooding. The
pattern favorable for this looks to continue into next month.
(Ensemble
total precipitation anomalies in Asia through August 23th).
4:50
pm CDT Tuesday: Edited to add the total precipitation anomaly map for
Asia.
---Meteorologist
Nick Humphrey
