winterforecast20112012
Post on 15-Jan-2015
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Official 2011-2012 Winter Forecast
2010-2011
Moderate/Strong La Nina Conditions Strong blocking (-NAO) dominated
conditions for December & January Dominantly –AO and +PNA Above Normal Snowfall Much colder than average December
and January; warmer than average February
2011-2012 Overview
Weak La Nina ENSO Conditions Predominate –NAO; strong blocking -AO, +/- PNA, +AMO, -PDO, -QBO Low Solar Activity Amplifying winter pattern towards the
end of November Southeast ridge may become a factor
Overview (cont.)
Slightly Below Normal to around average temperatures
Cold December/January, warm February
Well above average snowfall Equal Chances for precipitation
Snowfall Prediction
Winston-Salem – 15” (Avg – 9”) Greensboro – 13” (Avg – 8.9”) Raleigh – 11” (Avg – 7”) Hickory – 12” (Avg – 7.2”) Charlotte – 7” ( Avg – 5.4”) Asheville – 22” (Avg – 15.4”) Atlanta – 4.5” (Avg – 2”)
ENSO Conditions
Currently a weak La Nina Forecasted to strength into a Moderate
La Nina I currently do not believe it will
strengthen to anything more than a strong weak Nina.
After this winter, ENSO conditions are forecasted to go positive/neutral.
ENSO Conditions (cont.)
CFS model strengthens Nina into the strong category, but that seems a little bullish at this juncture
I do expect the Nina to position itself more east per the current SST anomalies.
Current ENSO SST Chart
North-Atlantic Oscillation
One of the trickiest Oscillations to forecast
A HUGE determinate for wintry weather in the south
Normally a negative means good news for the south in terms of snow, a positive NAO does not.
Really hard to predict/forecast more than a week or two in advance
NAO (cont.)
If NAO is strong enough, it can override ENSO. Most notably last winter season.
I do expect a large part of this winter season to be dominated by a negative NAO.
A moderate, West-based NAO looks like the most viable option; this is one good for snow and cold in the east/south.
NAO (cont.)
I think that the –NAO will dominate most of December and January (with some relaxes, not many)
The pattern should relax more in February, much like it did last year
Overall, the NAO will likely again, set the stage for wintry weather here in the south
Arctic Oscillation
Increased snow cover causes some increased stratospheric warming, due to the thermal effect
This, in turn causes the Siberian High to strengthen, which allows the Arctic jet stream to dig south every-now-and-then, causing what we call massive arctic air outbreaks.
AO (cont.) Normally as winter progresses, high
pressure anomalies are found in the arctic, while low pressure anomalies are found around the mid-latitude oceanic regions
While this occurs, the energy transfer from the upper to lower parts of the atmosphere weakens, in turn allowing for a more north-south flow instead of an east-west flow
AO (cont.)
All of this allows warmer air to enter the polar parts of the atmosphere
All of this is strongly connected to the NAO.
Currently .82, which is really high This is going to lead to another
negatively-dominated AO, which is another good sign for wintry weather here in the south
Quasi-Biennial Oscillation QBO is another Oscillation we look at to
determine possible blocking This oscillation is located slightly above
the equator Winds normally blow west during a
positive phase, and east during a negative phase
It is forecasted that the QBO will be in a weak/moderate negative phase for the upcoming winter
QBO (cont.) During this phase we can expect the
polar vortex to weaken, with an increased potential for SSW (Sudden Stratospheric Warming)
SSW increases high latitude blocking potential, and it helps develop a –AO
The QBO is a big determinate to the NAO. We should continue to monitor this as we get closer to December for a more accurate forecast
Pacific Decadal Oscillation Dominate negative phase for the last
couple of years of this cycle There is evidence of this with the cooler
anomalies in the Gulf of Alaska as well as warmer anomalies located more west of that area
Atlantic Multi-decadal Oscillation This is the index that refers to the SST
anomalies in the North Atlantic region, normally from the equator to 70o N.
In 2005 the AMO peaked, and has been on the decrease since then
During it’s warm phases, it makes the water warmer than normal, and cooler than normal during its cool phases
AMO (cont.)
This winter, the AMO is expected to continue to be in the positive phase, albeit weakening
It should become neutral/negative sometime between 2015-2020
Climate Indices
Current Fall Pattern
We have seen many deep toughing scenarios, with snow in Colorado, Texas, Oklahoma, Nebraska, Kansas, and the Northeast, all before Halloween
In the SE, we have already seen many CAD events, which leads me to believe, this will somewhat be the pattern throughout most of the winter
Fall Pattern (cont.)
With that which comes with CAD is ice In the SE it has been several winter
seasons that we have made it out without a major ice storm, but our luck may have ran out
With these frequent strong High Pressure systems wedging cold air against the mountains, we are just asking for a major ice storm
Fall Pattern (cont.)
Current models are leading to the possibility of some prolonged blocking beginning towards the end of the month, through at least the first half of winter
There is no guarantee, but I do expect a pattern to establish itself, much like the one we saw last December; lots of cold and snow.
Temperature Forecast
Precipitation Forecast
Snowfall Forecast
Final Word Winter should start within a few weeks, without
much notice I am excited of the possibility of a 3rd
blockbuster winter in a row, with well above average snowfall and below average temperatures
I expect the first winter storm to be within the first 10 days of December, but that’s just my guess.
Lastly, I hope everyone enjoys this winter, and any snow/ice that you get!
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