Wednesday, November 6, 2013

2013-2014 Official Winter Forecast

Part I:Teleconnections
NAO
As many of you know, the Northern Atlantic Oscillation is a big time driver during the winter months that could bring big snowstorms to the east coast, as well as bring record high temperatures. Unfortunately, there aren't any definite indications that would hint at significant blocking from the NAO but there are a few.

Turning to the waters near Greenland, you can find warmer than average waters just to the west and under Greenland which is a good indication that ridging could be more likely than not during the winter months but these waters aren't as warm as you would want them to be to have a clear indication of ridging dominating much of the winter in the area. None the less, its still a plus if your rooting for a negative NAO. Also, low sunspot activity for majority of this year is also a big plus as this typically allows for more high latitude blocking to occur during the winter months but mid October the sun begun to become active and as i write this, it continues to shows activity. With that being said, this could certainly reduce your chances of seeing blocking from the NAO, but this would have to continue for a longer period of time rather than a couple of weeks.
AO
Much like the NAO, the Arctic Oscillation is just as big of a factor, if not bigger. This oscillation is your mailman when it comes to the cold air! This oscillation controls where the cold air goes. When the AO is positive, most of the cold air is bottled up in the polar region, but when the AO is negative, it brings cooler than normal air into the lower 48(sometimes into Siberia, but thats during a cross polar flow which is set up via the upper level pattern). Unlike the NAO, there are plenty of factors that indicate the AO being negative(which brings the cold air into the US) for majority of the winter season.
This chart in simpler terms shows how much ice is present in the Northern Hemisphere. Although this doesn't really effect where the cold air goes in the northern hemisphere, it does show that there is a lot of cold air present, which means there is more colder than normal air for us to tap into if the Arctic Oscillation does indeed move negative this winter.
The Northern Hemisphere snow cover has been studied to to have an effect on the Arctic oscillation during the winter months by reflecting what happens during the month of October. When you see continuous above average readings through out the month of October, this could lead to a continuous negative oscillation during the winter months. Now, this doesn't mean record amounts of negative readings from the Arctic Oscillation, this just means more confidence in having a negative AO more times than a positive one.
PNA
The PNA isn't as big of a factor like the NAO, and AO but this is still an important thing to note during a winter forecast as this 99% percent of the time could show were ridging and troughing is present in the united states.
Right now, there is a really good indication of the PNA being neutral to positive for much of the winter months judging by the warmer than normal waters in the pacific ocean. These waters are expected to continue to warm over the winter months which is why I'm confident in ridging continuing in the pacific which would allow for a trough to try to set up in the Midwest/East coast.
PDO
The Pacific decadal oscillation is also another driver in the weather pattern during the winter months and over the last few months i really dug into data and tried to figure out just how the PDO well effect us during this winter. Long story short, i dug deep enough to find some years just like this one regarding the PDO and the ENSO cycle and what i found was actually some good news. Currently the PDO values are running slightly negative and once again by data, this would mean warmer than average conditions for the east coast........ not so much, in fact i found out that even when you have slightly negative values(running from -0.8 to -0.1) during a warm neutral ENSO year, you end up with a winter like this one...
Also, these warmer than average waters in the Pacific are slowly but surely trying to warm over some of these cooler than average temperatures in the PDO region but judging by the main area of warmer than average waters, which is under Alaska, i don't think the PDO region will warm much more than it is. Speaking values, i don't think the PDO will get over 0.3 to 0.6. Even if this was the case, it would only add to the confidence in a cooler than average east. QBO
The Quasi-Biennial Oscillation is a periodic wind reversal near the equator which is influenced by atmospheric waves that start in the tropical troposphere, progress northward into the stratosphere. The study of the QBO has made it aware to be a major influence during the winter months.
Typically you would want to see a east based QBO(Negative QBO) during the winter months which promotes cold in the eastern portion of the US, but the current state of the QBO would be positive, which again, by statistic would lead to a warmer winter. BUT research shows the coldest winters judging by the QBO occur during values ranging from -8 to +8 and this months value is at +11.69 which confirms this weakening positive QBO. Over the last 3 months , this positive QBO has been on a decline and could end up in this +8 to -8 range by mid winter, only to enhance the cold prospects for this winter. Even though this QBO is weakening into a possible cold pattern, its still in a phase 6 positive reading.
(These maps were created by a meteorologist by the name of Michael J. Ventrice to sorta simplify the QBO)


Here you can see the QBO clearly in phase 6 and judging by its composite, could mean the chance at seeing a southeast ridge developing for the first half of winter as i expect this QBO weakening over time.

Part II: ENSO

Current ENSO cycle would suggest we should remain in the neutral territory but a warm neutral at that. By textbook, this means that the ENSO shouldn't have much effect on the weather pattern across the nation but having a warm neutral ENSO that's continuously warming in regions 4 and 3.4 could indicate a possible west based El Nino type pattern.
This circled region shows these warmer than average water anomalies approaching the surface and in fact, some models are indicating these waters to continue to warm but judging by the time of the year, i do not expect much of an effect from this warming over the eastern us for the first half of winter, although if the ENSO does indeed make it into weak El nino category, then winter could be a whole new ball game by the second half of winter. This is something that i will have to continue to monitor over the first half of the winter so make sure you like my facebook page just in case of changes!

Part III : Atmospheric Conditions
The state of the stratosphere can often hint at what type of conditions could be evident along the surface, let me explain that a little bit more in depth. 2 things can happen in the stratosphere that could cause different types of weather patterns across the world and that's when the stratosphere warms or cools. I could write a 10,000 word article on what the stratospheric conditions could do to the weather across the lower parts of the atmosphere so in simpler terms, warming along the stratosphere allows for below normal heights near the surface, and the opposite for when the stratosphere cools.
This chart shows 50mb temperature comparison to average in the stratosphere and the first thing i want to point out would be the time frame of Nov to mid Dec of last year. You notice that the red line is slightly below the dotted green line representing the atmosphere being cooler than normal along these dates. Any one remember how warm this time frame was last year? This is because with cooling occurring in the stratosphere, it lead to higher heights(above average conditions) across much of the US. The next time frame i would like to point out is between mid January and mid February, any one remember how cold this period was? You should catch were I'm going with this. Now the final thing to look at is the current time frame and as you can see, the stratosphere is running at are slightly above average in temperatures.
According to the GFS, the stratosphere is expected to continue to warm.

Conclusion: Stratospheric conditions would support the idea of high latitude blocking trying to set up along the northern hemisphere allowing cooler than normal temperatures to attempt to spread across a portion of the lower 48.
Part IV: Outlook
Temperatures
Snowfall
Not yet confident in snowfall for the east coast just yet. There certainly be opportunities for snow events, just not sure how much. Remeber one good storm in the south and these areas could easily be above average and i do believe this is possible.
Part V: Summary
December
Northeast- Around average
Midwest -Slightly to well below average, most of the snow events will be located in this region.
South-East- Near normal to slightly above average, possibly drier than normal as well
South- Near normal
Pacific -Northwest Slightly cooler than average, very wet
Pacific Southwest- Near normal
January
Northeast- Slightly below average temperatures, potential for multiple storm systems
Midwest- Slightly below normal, possibly drier than usual
South-East- Best chance for cold and snow in this region
South- Near normal to slightly below normal, wet conditions
Pacific Northwest- Warm and wet
Pacific Southwest- Warm and dry
February
Northeast- Slightly below average temperatures, moderating to normal. Potential for a few snow events
Midwest- Constent below normal temperatures, potential for a few snow events
South-East- Near normal to slightly below normal, very active sub tropical jet, wet
South- Near normal, wetter than usual
Pacific Northwest- Warm and dry
Pacific Southwest- Warm and dry

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