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Talking October 2012, its never too early


Rainshadow

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Between the super typhoon and the big mountain torque event, I don't see how we don't stay blocky through at least Oct 15

Well that would be good to remove warm Octobers (top third) during weak el ninos from the list. Of the 5, three ensuing winters were warmer than the current normal, one was warmer than the long term median and only one was cold (1919-20). Weak el ninos and "normal" Octobers were a 50/50 split.

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Between the super typhoon and the big mountain torque event, I don't see how we don't stay blocky through at least Oct 15

could you break down how to read and what the mountain torque means in terms of weather? Like for instance the MJO has each phase that plays a different role on storm development and temperatures for the area. Is Mt torque more of a thing where it helps jump start or get the ball rolling for -nao developments or what not?

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could you break down how to read and what the mountain torque means in terms of weather? Like for instance the MJO has each phase that plays a different role on storm development and temperatures for the area. Is Mt torque more of a thing where it helps jump start or get the ball rolling for -nao developments or what not?

In general, positive mountain torques lead to more zonal flow initially, then more meridional flow in the medium range (and vice versa for negative mountain torques).

The schematic I use in my head is a positive mountain torque adds more angular momentum to the atmosphere, which then makes baroclinic instability more likely, meaning wave breaking events are more likely. Adding the angular momentum makes the flow more zonal, the wave breaking makes the flow more meridional.

The last piece is determining where the wave breaking will occur. Himalayan mountain torques are correlated with the EPO and mountain torques from the Rockies are correlated to the NAO.

MTs aren't the be-all end-all (e.g. the MJO is a stronger teleconnection), but they are one more piece in helping nail down the MR forecast.

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In general, positive mountain torques lead to more zonal flow initially, then more meridional flow in the medium range (and vice versa for negative mountain torques).

The schematic I use in my head is a positive mountain torque adds more angular momentum to the atmosphere, which then makes baroclinic instability more likely, meaning wave breaking events are more likely. Adding the angular momentum makes the flow more zonal, the wave breaking makes the flow more meridional.

The last piece is determining where the wave breaking will occur. Himalayan mountain torques are correlated with the EPO and mountain torques from the Rockies are correlated to the NAO.

MTs aren't the be-all end-all (e.g. the MJO is a stronger teleconnection), but they are one more piece in helping nail down the MR forecast.

where can you get the forecast for them? and how did you read a map of the Mtn torque?

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where can you get the forecast for them? and how did you read a map of the Mtn torque?

Here is the link for MT analysis: http://www.esrl.noaa.gov/psd/map/images/reanalysis/aam_total/gltaum.90day.gif

There really isn't a forecast product for them. The Himalayan torques can be tied to the MJO (P4/5 is usually a positive torque event), but otherwise, you have to wait until you see them (well, at least I do, maybe some other people can forecast them). The good news is: they're a 8-14 day leading indicator of the synoptic flow, so you don't necessarily need to forecast them all that well.

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Mark is going to crunch the numbers, but since 1967 outside of the two big snow cover Octobers and nina Octobers, not seeing an eye popping temp correlation for us locally. Maybe the Euro part of Eurasian is skewing the stats.

BUT, given the current 22.4" normal, there have been 15 above normal seasons and 29 below current normal seasons since 1967 (granted there are a number of them around 20"). Have greater coverage of snow in October, your chances for an above normal season rises to 50%, have a below normal coverage of snow for October, it drops to 18%.

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