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The Medium Range Thread


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Asian mountain torques continued through the end of last week. I'm still expecting the AO to go negative sometime around Valentine's Day, despite what some of the dynamical guidance is showing right now. Even with the SE ridge in place, I don't think the Northeast, Great Lakes, or Northern Plains will see any prolonged periods of warmth. However, with little in the way of Atlantic blocking expected, I'd guess the primary storm track will be west of the Appalachians mid-month.

The 00z ECWMF seems to vaguely agree with your thoughts... by 240 hours, there is the first real concrete signs of blocking returning over Greenland. Euro Ensembles are not quite on board though.

w88ioh.gif

2dtofhk.gif

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And the ensembles are just as cold, if not colder.

I will record my first <32F this week . My location has probably averaged around a little less than 2 <32F days per season this century (none colder than 26F), and in 9 days I might rake 5 or 6 of those.

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Wouldn't that pretty much make 2010-11 one of NYC's top all-time winters?

For snow lovers, NYC area has been incredibly spoiled over the last 10 years. :lol:

making up for the 70s and 80s lol. I was in grade school in the late 80s and early 90s, and we didnt have a single snow day and I still remember our teachers in HS telling us that we should treasure every snowflake because snowstorms were becoming an endangered species and pretty soon the only places getting snow would be the far north and elevated locations. :arrowhead:

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Here is one example of the statistical MJO forecast I talk about occasionally.

fmaps.7day.MJO.gif

This is consistent with -WPO/+EPO/-PNA pattern that is coming up in the next couple of days. However, with the coherence of the MJO wave continuing eastward, I'd expect blocking in the Pacific to start propagating eastward again so that the EPO goes negative again around Valentine's Day. Combine that with the expected polar vortex disruption due to Asian mountain torques and I don't think we'll be seeing sustained warmth across the Northern Plains, Great Lakes or Northeast anytime soon.

The SE ridge is likely to finally come in around the 10th, so I'd imagine the SE, at least, will be able to escape the cold anomalies they've seen this year.

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Adam,

any chance this will further increase the chances for a Greenland block? So far, the signs aren't too ideal for it.

Like I posted in the PHL/NYC thread, the reforecast ensembles have it, but I don't see the forcing for it, unless it is just a consequence of the -AO. By the end of Feb, the MJO should be in Phase 7 or 8, which would be more favorable from a tropical forcing perspective.

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Here is one example of the statistical MJO forecast I talk about occasionally.

fmaps.7day.MJO.gif

This is consistent with -WPO/+EPO/-PNA pattern that is coming up in the next couple of days. However, with the coherence of the MJO wave continuing eastward, I'd expect blocking in the Pacific to start propagating eastward again so that the EPO goes negative again around Valentine's Day. Combine that with the expected polar vortex disruption due to Asian mountain torques and I don't think we'll be seeing sustained warmth across the Northern Plains, Great Lakes or Northeast anytime soon.

The SE ridge is likely to finally come in around the 10th, so I'd imagine the SE, at least, will be able to escape the cold anomalies they've seen this year.

Not at all what I was hoping to see (hear) - but thanks for the analysis!

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The polar vortex disruption that Jorge and I have been talking about is ongoing. Here are the temperature and zonal wind anomalies in the polar regions.

time_pres_TEMP_ANOM_JFM_NH_2011.gif

time_pres_UGRD_ANOM_JFM_NH_2011.gif

Model forecasts show the wave forcing weakening by next weekend as the Asian mountain torque event is drawing to a close.

ecmwfzm_ta1_f168.gif

Both the GFS and ECMWF are showing the vortex being displaced into our hemisphere as we head towards Valentine's Day, though. That would be indicative of a -AO pattern.

ecmwf30f240.gif

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Today's GEFS D+11 mean isn't that far off from the pattern I expect around Valentine's Day.

814analog.off.gif

After this period, you should see the ridge amplify along or offshore of the West Coast for the 2nd half of the month.

Some great backend winter analogs in that list AMPSU. Specifically looking at 1955-56 and 1966-67.... really fits in with the snowy March idea (and perhaps even latter part of February.)

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It does look like we get some sort of a reprieve for several days perhaps as we head towards the 11-15 day. However, after that time..there are signs of a -nao trying to develop along with a more west based -epo ridge. This may turn the country colder once again beyond mid month. I know it's two weeks out, but that's been a signal for a few days it seems. The MTN torque events and perhaps the SW also will have to be watched, but these events may just be starting to be felt my numerical guidance.

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The Don S warm surge after Valentine's Day is well modeled this morning

814analog.off.gif

This map makes me barf. Gotta agree that the negative PNA is coming, though the USA truly got its money's worth out of the first few days of Feb (and probably until next Thu as well!)

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Are you speaking "from your gut" or do you have data to back up your claims?

Yes, there could be a warm period for a week or so, but indications are a cooler regime will return to the east/south to end the month and start March.

I'm on the boat that winter ends for the Deep South after next weeks cold air shot. Barring a March '93-like superstorm, things down south look rather warmish past Feb 12th until next winter.

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Are you speaking "from your gut" or do you have data to back up your claims?

Yes, there could be a warm period for a week or so, but indications are a cooler regime will return to the east/south to end the month and start March.

I'm not including the east, just sincluding the Deep South (TX, LA, AL, MS, GA, FL). Almost every winter ends with February in those states, yeah, it might be colder (not even sure about that, but there are reasons to think it might), but widespread subfreezing/wintry precip is rare in March. With a SE ridge establishing the second half of Feb, with no real favorable MJO wave in sight, nor real super strong high latitude ridging before March, and a negative to neutral PNA, I'm thinking of no more widespread cold.

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I'm not including the east, just sincluding the Deep South (TX, LA, AL, MS, GA, FL). Almost every winter ends with February in those states, yeah, it might be colder (not even sure about that, but there are reasons to think it might), but widespread subfreezing/wintry precip is rare in March. With a SE ridge establishing the second half of Feb, with no real favorable MJO wave in sight, nor real super strong high latitude ridging before March, and a negative to neutral PNA, I'm thinking of no more widespread cold.

CPC ends winter, mid-month:

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This map makes me barf. Gotta agree that the negative PNA is coming, though the USA truly got its money's worth out of the first few days of Feb (and probably until next Thu as well!)

And the vast majority of the eastern US has got more than their money's worth this winter. No room to complain for most. :snowman:

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It does look like we get some sort of a reprieve for several days perhaps as we head towards the 11-15 day. However, after that time..there are signs of a -nao trying to develop along with a more west based -epo ridge. This may turn the country colder once again beyond mid month. I know it's two weeks out, but that's been a signal for a few days it seems. The MTN torque events and perhaps the SW also will have to be watched, but these events may just be starting to be felt my numerical guidance.

This is still looking good, though delayed. There are some signals of a ridge retrogressing from Western Europe towards Greenland around the 17th. If that occurs, that will set up a battleground in the Mid-Atlantic (DC/PHL) between the -NAO and SE ridge.

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This is still looking good, though delayed. There are some signals of a ridge retrogressing from Western Europe towards Greenland around the 17th. If that occurs, that will set up a battleground in the Mid-Atlantic (DC/PHL) between the -NAO and SE ridge.

Yeah I was just talking about this in the sne thread. I think we definitely should not be rushing the change, after all..it seems like models always do this, but we know to usually back off from the change for several days at least. The -NAO progged is fairly weak on the EC ensembles, but might be enough to sink that boundary south into the nrn tier of the US.

I think there are still some questions, so my guess is that we'll have a better idea on what may happen, a week from now. It seems the MJO forecasts don't offer much of a strong signal either.

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This map makes me barf. Gotta agree that the negative PNA is coming, though the USA truly got its money's worth out of the first few days of Feb (and probably until next Thu as well!)

Psshhh.

I've had 0 snow so far this winter. Okay, a couple light dustings, but it's my turn already!

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