An Overview
The pattern so far this November has featured abrupt climate changes that have resulted in a roller coaster ride in temperatures this month. Don't take off your seatbelt yet because the ride has not ended but down the road it appears apparent a more dominant and controlled pattern will take hold that will put an end to this extremely bumpy and fluctuating pattern thus far. Let's break it down in the short/mid/long range aspects to view how the overall evolution will occur.
Short Range:
Short range presents some interesting aspects as of late in the tri-state area the weather has been above average in temperatures these last few days following a few colder days that brought a transitional blast of cold air but once this dissipated and the trough departed and the warmer weather has return and so has the rain. Today we saw copious amounts of rainfall as well as very strong wind associated with the nor'easter. The pressure dropped low in response there was a tight iso-bar gradient however the bulk of the winds were from a strong vort max crossing the area in association with the colder air and winds aloft (250mb) because no strong high was situated to the NW therefore the strong winds were more a result of frontogenesis within the lower levels from the affects of adiabatic warming and cooling which created vertical motion and stronger winds. Of course we can't discount how strong the system was and its relative location to our area.
The effects from the system can already be felt as it tugged in much colder air behind it and established a deep trough in the eastern United States that gave interior and northern sections of the northeast some good snows. Also the winds off the waters (lakes) have resulted in Lake Effect Snow for the areas usually prone to is such as NY, VT, PA. The warm waters that are still unfrozen coupled with the cold air aloft creates the most suitable and conducive conditions to good LES events.
Expect a Clipper to swing down into the tri-state area by Wednesday night which will start off with some snow however coastal areas including the city will most likely see a change to some rain Thursday. Remember however that clippers don't pack much moisture and are fast moving so it will most likely quickly depart by later Thursday. No snowfall accumulation expected in the city however inland areas may see a trace to an inch or so. The problem is that this clipper will result in minimal temperatures and an oceanic influence should warm up the surface temperatures Thursday. As the clipper cutts inland it will allow the winds to turn Sand E off the water not only pumping up the heights and temps but allowing the oceanic influence. For this reason see it hard for any accumulations to occur in coastal areas including NYC however inland where temps should be somewhat cooler and areas of higher elevation should see minimally more optimal conditions for some snow that may accumulate slightly especially those areas prone to orographic lift which can enhance the snow. Also the thermal differential between the water temps and air temperatures will allow storms the potential to "blow up" a bit more and throw up a little more moisture.
Temperatures from Wednesday through Friday will not exceed 40 degrees except for the exception of Thursday which for factors and reasons I already mentioned may by a smidget pass 40 degrees.Thanksgiving Forecast for NYC: Light snow in the morning hours followed by a mix of some rain and snow mainly light. High Temperature of 42 degrees. Slight breeze associated with the clipper low 4-9mph in correspondence with the strong vorticity.
Mid Range (11/26-12/1):
As this low moves into Canada there is some Greenland ridging that may help to establish some blocking features which can ultimately effect other factors such as North Atlantic Oscillation or difference of sea level pressure and heights between Iceland and the Azores. This would help to maintain the troughiness however it appears that any ridging will not become sustained and will dissipate to allow the block to fall apart and the trough or colder air over the northeast to moderate as a result of a dominant Pacific flow. Some moderation will really start to occur around the 27th however this will not be a trend. In the 11/28-12/2 timeframe a single or series of strong lows will cut into the interior of central United States (possible infux temps (ridge) ahead of systems associated with trough (S wind influence) only because the blocking has dissipated to allow this to occur. This event however is significant because it will pull down the colder heights into the western United States which will retrograde with the pattern east and the succession of storms will convolute the Pacific or break it down and eventually result in the formation of a blocking pattern and make the Atlantic suitable for a winter type setup pattern however this will really occur in the long range but the factors and elements are present in the mid range.
Long Range (12/2-12/6):
Ridge in association with the PNA should pump ridge out west downstream the results are amplification of the trough and with the block in place from the inland cutting storms the PV and vortex should slide S and E towards the Hudson Bay. The pattern than will continue to improve and shortwaves will reamplify the trough and blocking will keep the eastern United States in a troughy pattern. As far as storminess its hard to pinpoint however with a possible rex and split flow I would not be surprised to see how some STJ interaction between 12/4-12/7 however the exact pinpoint details at this time is silly but with the pattern I feel its possible to see a SECL in the 12/4-12/7 period. Factors continue to improve especially as a result of the blocking etc.
Current Indixes:
22Nov2005 -0.61909E+00 0.12193E+01 0.67667E+00 -0.14159E+01 AO NAO PNA AAO
NAO was negative a bit ago while some blocking was established and there was more troughiness expect a return to slightly positive or negative values during this next bout of temporary blocking and troughiness than possible another period of return to positive between 11/27-12/3 and then possibly negative again after blocking occurs and pattern changes 12/4+. Helps to prevents the blowout of the pattern by the Pacific. PNA will be the result of the western ridge and downstream amplification of eastern trough. AO or Atlantic Oscillation should follow in becoming improved.
http://www.nco.ncep.noaa.gov/pmb/nwprod/analysis/namer/gfs/12/fp0_384.shtml
http://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/daily.index.ascii
Quick Notes:
I will post another updated outlook tomorrow on the clipper to discuss any changes or new ideas and I also from now on won't just throw everything together I will explain maps and models etc. as opposed to just including the links like this time because of lack of time. When I have more time I will also go more in depth on the indixes and pattern for those more skilled. Sorry for this quick unorganized writeup due to lack of time. Also watching new trends on models going colder with the clipper maybe more optimistic for the clipper will see tomorrow! Thats all for now.
Brian - Meteo101 and the NYMetroWx Forecasting Team
The pattern so far this November has featured abrupt climate changes that have resulted in a roller coaster ride in temperatures this month. Don't take off your seatbelt yet because the ride has not ended but down the road it appears apparent a more dominant and controlled pattern will take hold that will put an end to this extremely bumpy and fluctuating pattern thus far. Let's break it down in the short/mid/long range aspects to view how the overall evolution will occur.
Short Range:
Short range presents some interesting aspects as of late in the tri-state area the weather has been above average in temperatures these last few days following a few colder days that brought a transitional blast of cold air but once this dissipated and the trough departed and the warmer weather has return and so has the rain. Today we saw copious amounts of rainfall as well as very strong wind associated with the nor'easter. The pressure dropped low in response there was a tight iso-bar gradient however the bulk of the winds were from a strong vort max crossing the area in association with the colder air and winds aloft (250mb) because no strong high was situated to the NW therefore the strong winds were more a result of frontogenesis within the lower levels from the affects of adiabatic warming and cooling which created vertical motion and stronger winds. Of course we can't discount how strong the system was and its relative location to our area.
The effects from the system can already be felt as it tugged in much colder air behind it and established a deep trough in the eastern United States that gave interior and northern sections of the northeast some good snows. Also the winds off the waters (lakes) have resulted in Lake Effect Snow for the areas usually prone to is such as NY, VT, PA. The warm waters that are still unfrozen coupled with the cold air aloft creates the most suitable and conducive conditions to good LES events.
Expect a Clipper to swing down into the tri-state area by Wednesday night which will start off with some snow however coastal areas including the city will most likely see a change to some rain Thursday. Remember however that clippers don't pack much moisture and are fast moving so it will most likely quickly depart by later Thursday. No snowfall accumulation expected in the city however inland areas may see a trace to an inch or so. The problem is that this clipper will result in minimal temperatures and an oceanic influence should warm up the surface temperatures Thursday. As the clipper cutts inland it will allow the winds to turn Sand E off the water not only pumping up the heights and temps but allowing the oceanic influence. For this reason see it hard for any accumulations to occur in coastal areas including NYC however inland where temps should be somewhat cooler and areas of higher elevation should see minimally more optimal conditions for some snow that may accumulate slightly especially those areas prone to orographic lift which can enhance the snow. Also the thermal differential between the water temps and air temperatures will allow storms the potential to "blow up" a bit more and throw up a little more moisture.
Temperatures from Wednesday through Friday will not exceed 40 degrees except for the exception of Thursday which for factors and reasons I already mentioned may by a smidget pass 40 degrees.Thanksgiving Forecast for NYC: Light snow in the morning hours followed by a mix of some rain and snow mainly light. High Temperature of 42 degrees. Slight breeze associated with the clipper low 4-9mph in correspondence with the strong vorticity.
Mid Range (11/26-12/1):
As this low moves into Canada there is some Greenland ridging that may help to establish some blocking features which can ultimately effect other factors such as North Atlantic Oscillation or difference of sea level pressure and heights between Iceland and the Azores. This would help to maintain the troughiness however it appears that any ridging will not become sustained and will dissipate to allow the block to fall apart and the trough or colder air over the northeast to moderate as a result of a dominant Pacific flow. Some moderation will really start to occur around the 27th however this will not be a trend. In the 11/28-12/2 timeframe a single or series of strong lows will cut into the interior of central United States (possible infux temps (ridge) ahead of systems associated with trough (S wind influence) only because the blocking has dissipated to allow this to occur. This event however is significant because it will pull down the colder heights into the western United States which will retrograde with the pattern east and the succession of storms will convolute the Pacific or break it down and eventually result in the formation of a blocking pattern and make the Atlantic suitable for a winter type setup pattern however this will really occur in the long range but the factors and elements are present in the mid range.
Long Range (12/2-12/6):
Ridge in association with the PNA should pump ridge out west downstream the results are amplification of the trough and with the block in place from the inland cutting storms the PV and vortex should slide S and E towards the Hudson Bay. The pattern than will continue to improve and shortwaves will reamplify the trough and blocking will keep the eastern United States in a troughy pattern. As far as storminess its hard to pinpoint however with a possible rex and split flow I would not be surprised to see how some STJ interaction between 12/4-12/7 however the exact pinpoint details at this time is silly but with the pattern I feel its possible to see a SECL in the 12/4-12/7 period. Factors continue to improve especially as a result of the blocking etc.
Current Indixes:
22Nov2005 -0.61909E+00 0.12193E+01 0.67667E+00 -0.14159E+01 AO NAO PNA AAO
NAO was negative a bit ago while some blocking was established and there was more troughiness expect a return to slightly positive or negative values during this next bout of temporary blocking and troughiness than possible another period of return to positive between 11/27-12/3 and then possibly negative again after blocking occurs and pattern changes 12/4+. Helps to prevents the blowout of the pattern by the Pacific. PNA will be the result of the western ridge and downstream amplification of eastern trough. AO or Atlantic Oscillation should follow in becoming improved.
http://www.nco.ncep.noaa.gov/pmb/nwprod/analysis/namer/gfs/12/fp0_384.shtml
http://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/daily.index.ascii
Quick Notes:
I will post another updated outlook tomorrow on the clipper to discuss any changes or new ideas and I also from now on won't just throw everything together I will explain maps and models etc. as opposed to just including the links like this time because of lack of time. When I have more time I will also go more in depth on the indixes and pattern for those more skilled. Sorry for this quick unorganized writeup due to lack of time. Also watching new trends on models going colder with the clipper maybe more optimistic for the clipper will see tomorrow! Thats all for now.
Brian - Meteo101 and the NYMetroWx Forecasting Team
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