Today's Featured Post: Updated Long Range Outlook Will be Issued Wednesday at 4:30 PM Central Time.

Thursday, November 3, 2011

2011-2012 Winter: Mid-Upper Level Atmosphere Temperatures at Record Lows

Mid to Upper levels of the atmosphere are currently experiencing all time record lows. As seen in the graph above, you can see how this is the lowest temperature for this time of year in at least the past several years graphed here. Not only is that true, but the same lowest temperature claim can be said for all temperature readings at this time of year since recording began.

What does this mean?
Warm air from storms of any nature rise into the atmosphere. In the summer, this creates instability for thunderstorms. At this point in time going into winter, if these record low temperatures are to continue, one could infer that the warm air rising from a low pressure system would rise higher and faster in the atmosphere, thus creating more energy for the system to work with and in turn creating more snow.


In our eyes, this is a very possible thing to happen. It aligns with basic physics rules and basic temperature movements in the air (warm air rises), so to say.
We will watch this, as it may have a big effect on winter snowfall this year.

NAO Ensembles Head for Negative Territory around Mid-November

Pre-reading notes: The NAO is a variating index which takes into account a semi-permanent high pressure system over the Azores (Azores High) and a semi-permanent low pressure system over Iceland (Icelandic Low). The higher the pressure differences are between this high and low means a +NAO index, while a low difference is a -NAO. -NAO typically gives cool air to the North US and areas around the region.

NAO tracking ensemble models are now in a consensus to head into negative territory beginning mid November. While that is not the official start of Meteorological Winter, it is around the time the Midwest, Plains begin to see their chances for snow significantly rise.
We will carefully watch the NAO and all other variables as we track this potential.

Storm Prediction Center Puts South US in Severe Weather 5 days in advance

In a move only characterized by very strong confidence and only happening a few times a year, the Storm Prediction center has placed the South US in the risk for severe weather 5 days in advance.
To the average person, this 5 days may not seem like much. But to the experienced weather forecaster, this means a lot. It means the SPC has an unusually high amount of confidence this will happen, as day 6 outlooks are rarely released this far out.
The following is the SPC's discussion. We have bolded the parts you as an everyday person will be able to understand, as this discussion is meant for more experienced weather folk.



ON SUN/D4...AN UPPER TROUGH WILL BE DEAMPLIFYING ACROSS THE UPPER MS
   VALLEY/GREAT LAKES REGION...WITH A BROAD BELT OF SWLY FLOW ALOFT
   EXTENDING SWWD INTO THE SWRN STATES INTO THE BASE OF THE NEXT
   TROUGH. WITH SLIGHTLY RISING HEIGHTS ALOFT...SWLY FLOW WILL INCREASE
   OVER THE PLAINS HELPING TO BRING GULF MOISTURE NWD OVERNIGHT.
   
   BY MON/D5...MODELS ARE IN GOOD AGREEMENT BRINGING THE UPPER TROUGH
   AND LEADING EDGE OF HEIGHT FALLS ACROSS THE FOUR CORNERS STATES AND
   INTO THE SRN HIGH PLAINS BY MON AFTERNOON. LOW PRESSURE IS FORECAST
   TO DEEPEN OVER THE TX PANHANDLE AREA...WITH SLY FLOW INTENSIFYING
   THROUGH THE DAY AND OVERNIGHT WITH A 50+ KT LLJ AND AT LEAST LOWER
   60S F DEWPOINTS INTO OK. THE GFS SHOWS A WARM FRONT ALONG THE KS/OK
   BORDER...BUT THE ECMWF SUGGESTS THIS FEATURE WILL BE MUCH FARTHER N
   INTO NRN KS/SRN NEB. WHILE THE NRN EXTENT OF ANY SEVERE THREAT MAY
   BE IN QUESTION...IT APPEARS LIKELY THAT SEVERE STORMS WILL OCCUR
   OVER PORTIONS OF WRN OK AND NWRN TX NEAR THE DRYLINE.  HERE...STEEP
   LAPSE RATE PROFILES SHOULD EXIST.  WHILE INSTABILITY WILL NOT BE
   PARTICULARLY LARGE WITH ONLY NEAR 60 DEWPOINTS...SHEAR PROFILES WILL
   BE QUITE FAVORABLE FOR SUPERCELLS DURING THE AFTERNOON AND EVENING.
   A FEW TORNADOES ALONG WITH HAIL AND WIND WILL BE POSSIBLE. 
   OVERNIGHT...A COLD FRONT WILL EVENTUALLY MOVE INTO CNTRL OK AND TX.
   IT IS POSSIBLE MORE CONVECTION WILL OCCUR ALONG THIS FRONT...BUT THE
   PRIMARY THREAT WILL LIKELY BE WITH DIURNAL SUPERCELLS.
   
   BY TUE/D6...MODELS START TO DIVERGE WITH THE ECMWF LIFTING THE UPPER
   LOW/JET MAX NEWD MUCH QUICKER THAN MANY OF THE MREF MEMBERS. EVEN
   WITH THESE DIFFERENCES...STRONG SWLY FLOW ALOFT WILL EXIST ATOP MID
   TO UPPER 60S F DEWPOINTS AND FORCING ALONG THE COLD FRONT AND
   DRYLINE. THUS...SOME RESIDUAL SEVERE THREAT IS LIKELY FROM E TX INTO
   AR AND LA WITH THE MAIN THREAT DAMAGING WINDS AND A FEW TORNADOES.