12/12/16 Winter Threat Assessment Blog – Storminess Leading Up to Christmas Week
Synopsis: First things first, for details on winter storms and weather in the 1-7 day range, email us at “Info@BAMwx.com” to sign up today! Welcome again for another update of the winter threat assessment blog! As we dig deeper into the next couple of weeks things start to get a little bit more difficult as for picking out specific systems in this pattern. There have been glimpses over the past 2 weeks of signs of a southeast ridge popping up near the week of Christmas and the more we dig into the latest data…the more we see evidence of this. Now, a southeast ridge can act as a “steering” mechanism to force systems into the Ohio Valley, and at the same time, when there is little to no blocking present (AO/NAO) it can force winter systems to the north and west of the Midwest even (depending on the strength of the -PNA).
(Image Source: TropicalTidbits.com)
Also, how we determine the strength of the southeast ridge is by looking at the strength of the PNA…below is the latest forecast of our teleconnections and we can see going forward deeper into December the trend is a negative PNA…below that is an illustration of what this pattern reflects at 500mb and near the surface.
Negative PNA (Image source: http://climate.ncsu.edu)…we can see the -PNA sets up a trough in the west and a ridge in the east, specifically the southeast ridge in this case. How strong the negative PNA sets up determines where the track of the winter systems move through the Midwest, Ohio Valley and Interior Northeast.
Next Targeted System (December ~23rd): This is the timeframe we are basing our next targeted winter threat that is 7+ days out…it gets trickier in this timeframe because of the influence of the southeast ridge.
Eastern Asia has a trough ~13th, so if we add the 6-10 days to this date we get our target date.
Just for additional support I wanted to show the CFS that has as trough digging in during this timeframe as well…so we do have multiple sources of data that suggests a winter storm during our target date.
Winter Threat Assessment:
Despite any fluctuations in temperatures over the next 2-3 weeks, we have solid data sources that tell us the pattern continues to be active…so check back often for updates to the blog!
Confidence and Risk:
- Increasing confidence of ridging starting to build across the southeastern US near Christmas week
- Average confidence we see a -PNA in the medium to long-range, which increases confidence of ridging
- Below average confidence in our system ~Dec 23rd given the volatility in the pattern we are still in and because the track of our system depends on the strength of the southeast ridge
Interested in getting the details any of these systems within 7 days, including timing, intensity, precipitation-type etc? Send us an email to “Info@BAMwx.com” expressing your interest and we will get you taken care of (both personal/commercial services as well)!
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