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Extreme cold over Siberia will drop toward China and allow a big temp gradient with Tropical Asia. This will surge a Jet out of the Pacific and make North America an active weather pattern. (you see this with the models already next 2 weeks)
MJO forecast will result in an up & down pattern for Ohio Valley but head into a Phase 8 for mid February which is a colder phase for Eastern U.S
PNA becomes positive for mid February also supporting a Western Ridge
Last cold was impressive because below 0F temps happened with a bare ground with storm tracks to the south.
Southeast ridge might be stronger this time around but this means more chances of wintry weather.
Quote:
Area Forecast Discussion
National Weather Service Louisville KY
329 PM EST Thu Jan 25 2018
Moving into Thursday, another storm system is poised to move the
region. This will bring rainfall to the region during the day on
Thursday. As colder air pushes in from the northwest, a switch over
to snow is likely Thursday night and will likely continue into early
Friday. Some accumulation of snow will be possible with this system
and it will be watched closely over the coming week.
Beyond Thursday and into February...
From a hemispheric view, large negative temperature anomaly
currently is centered over eastern Siberia. This will drop
southward into China over the next week and bring very cold weather
to much of east Asia. This will result in a very strong temperature
gradient down in the tropics of east Asia and allow the east Asia
Jet to surge out into the Pacific. The Pacific is expected to
remain fairly active, yet progressive in nature. The progressive
nature will lead to an active weather pattern across North America
through late January and into early February.
Currently the MJO resides squarely in the phase 4/5 phase space
which for January is a milder pattern for the eastern US. The
latest dynamical forecasts suggest that the MJO will translate into
the phase 5 and 6 pattern late this week and into next week before
getting into the phase 7 by early February. The net result locally
in the Ohio Valley will feature an up and down temperature pattern
with warm ups before weather systems followed by cool downs behind.
Experimental signal analysis completed earlier this week are in very
good agreement with a strong signal passing through the region at
the end of the long term period (mentioned above). Another series
of signals will cross the region in the 2/5-8 time frame which may
bring periods of active weather. A stronger signal looks to impact
the region the 2/10-12 time frame. Our analysis suggests that this
system may be the lead system that brings the resurgence of colder
into the region for mid-late month. The resurgence of a colder
pattern has been well advertised over the couple of weeks in the
RRWT (Recurring Rossby Wave Train) analysis along with the dynamical
modeling suggesting the MJO entering the phase 8 and then phase 1 by
mid-late month. For reference, MJO phase 8 and phase 1 strongly
correlate to much below normal temperatures for the eastern US in
February. Supporting the dynamical MJO forecasts are other
teleconnection patterns. The PNA pattern is expected to become
quite positive which results in a large amount of ridging over the
western US and results in a downstream trough across the east. In
addition, the Pacific is expected to see a mild/strong -EPO signal
which is also supportive of cold in the eastern US. The QBO signal
remains strongly negative which in a La Nina base state results in
cooler conditions across the eastern US.
While the cold signal seems to be well advertised in the extended,
there remains questions about the quantity of a moisture feed we`ll
see across North America during February. In the previous cold wave
(Late Dec/Early Jan) we saw the cold dominate and push the storm
track well to our south. So much of our cold was a dry cold and
impressive nonetheless with below zero temperatures over bare
ground. This time around may be different as tropical forcing may
keep the SE ridge a bit more pronounced. This is not surprising in
a background La Nina state. If that ridge can be a bit more
pronounced, we could see a pattern where deeper moisture from the
Pacific may get entrained into the southern branch of the jet
leading to the threat of more wintry systems from mid-late month
good morning, our warmth lately is from a non-zonal pattern unlike the last two winters. I'm guessing that's why mild + not too windy isn't happening in the mountains
Looks like winter is definitely over judging by the latest model trends. Hope we don't turn cold/wet in April or May, would like to see an early summer.
Looks like winter is definitely over judging by the latest model trends. Hope we don't turn cold/wet in April or May, would like to see an early summer.
La Nina years usually have bad springs. I hope for another spring of 2016 when it got warm and sunny in April.
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might change after 1st week though
