Ph.D. Student - Earth System Science (UC Irvine), B.Sc. - Atmospheric Sciences (Cornell University)
By: Zachary Labe , 8:47 PM GMT on November 20, 2011
Thanksgiving is just about here and the holiday shopping season has already kicked off in full swing! While no resemblance to winter outdoors, signs of the holiday month are dotting street corners and shopping malls. The first semester at Cornell is just about over with the last week of classes immediately following Thanksgiving. It has been a very busy period the last two weeks with mounting homework assignments and projects. In fact many of us spent our Saturday night at one of the libraries until they decided to close early that evening. And then my Sunday transforms quickly into a mob of people outside the library just as they are opening the doors. This is Cornell's black Friday. It will be refreshing to spend time back at home over the short Thanksgiving break away from the stresses of school. After the October record snowstorm, I know many people are antsy for the next snow. But it is only November and snowfalls are usually limited to the higher elevations. Here is a quick look at any pattern change in the foreseeable future...
Fig. 1- Temperatures anomalies for the last seven days as of November 12.
Noting current temperature anomaly maps, it is obvious that placement of a ridge over the east and trough over the east has been dominating the jet stream across the contiguous United States. This has been associated with unfavorable teleconnections including a +NAO which is associated with lower heights over Greenland and a weaker pressure gradient. This allows for a transient jet without any favorable blocking. A -PNA has also allowed for a very steep trough over the western United States.
Fig. 2- The GFS (GEFS) ensembles continue to indicate a high standard deviation positive EPO.
The +EPO has allowed for the unfavorable placement of an Alaskan polar vortex associated with near historic cold across parts of central Alaska.
NOAK49 PAFG 200954
PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE FAIRBANKS AK
1254 AM AKST SUN NOV 20 2011
...THE RECORD COLD CONTINUES AT FAIRBANKS...
THE COLD SNAP CONTINUES TO RE-WRITE THE RECORD BOOKS AT
FAIRBANKS. THE CURRENT COLD SNAP IS ONE OF THE MOST SEVERE ON
RECORD FOR SO EARLY IN THE WINTER SEASON. HAD THE COLD SNAP
OCCURRED IN DECEMBER...JANUARY...OR EVEN TOWARD THE VERY END OF
NOVEMBER IT WOULD NOT BE AT ALL UNUSUAL. WHAT MAKES THIS COLD
SNAP MORE UNIQUE IS THAT IT OCCURRED THE WEEK BEFORE THANKSGIVING.
SATURDAY WAS YET ANOTHER RECORD SETTING DAY AT FAIRBANKS. THE
HIGH OF 23 BELOW AT THE AIRPORT WAS ANOTHER RECORD LOW MAXIMUM
TEMPERATURE. THE OLD RECORD OF 22 BELOW WAS ESTABLISHED WAY BACK
IN 1911. THE LOW OF 36 BELOW BROKE THE RECORD OF 33 BELOW FROM
SATURDAY MARKED THE 5TH CONSECUTIVE DAY WITH A LOW TEMPERATURE OF
30 BELOW OR COLDER AT THE AIRPORT. THIS TIES WITH 1956...1969 AND
1989 FOR THE MOST CONSECUTIVE DAYS WITH A TEMPERATURE OF 30 BELOW
OR COLDER SO EARLY IN THE WINTER SEASON.
THE LOW TEMPERATURE HAS NOW BEEN 35 BELOW OR COLDER EACH OF THE
LAST 5 DAYS. THIS HAS NEVER HAPPENED BEFORE SO EARLY IN THE
WINTER SEASON AT FAIRBANKS. THE OLD RECORD WAS ONLY 2 DAYS...AND
WAS LAST RECORDED IN 1989.
THE HIGH TEMPERATURE HAS NOW BEEN 20 BELOW OR COLDER EACH OF THE
LAST 4 DAYS. THIS BREAKS THE RECORD OF 3 DAYS IN 1989 FOR THE
MOST CONSECUTIVE DAYS WITH A HIGH TEMPERATURE OF 20 BELOW OR
COLDER SO EARLY IN THE WINTER SEASON.
Given the unfavorable teleconnections, the MJO also has maintained a strong influence given the unfavorable phases 1-5 it has been circulating through the past few weeks.
Fig. 3- MJO phase 3 anomalies for November favoring warmth over much of contiguous United States.
So given the start of the meteorological winter will be beginning in a short two weeks, many snow lovers are certainly looking for some colder weather. Given many winter forecasts favoring a colder than normal December, many people are left wondering when the cold air will penetrate south of the Arctic.
The pattern currently is about as bad as it can get for snow lovers. The incredible and near record strength polar vortex south of Alaska is the kiss of death for Northeast snow. We need to see dramatic changes in the current wavelengths across North America and even into Asia. Looking at long term guidance, it appears that a pattern change may loom far in the future with finally some indication of a relaxation of the +EPO regime.
Fig. 4- The MJO GEFS prognostic indicates weaker forcing as we cycle through phases 4 and 5.
The current MJO prediction is to enter phases 3-5 over the next two week period. As noted in the graphic above, those phases tend to allow for a milder regime over much of the CONUS. But given the weaker forcing, we may be able to counteract the MJO with other teleconnections becoming more favorable.
Fig. 5- GEFS mean prognostic for 384 hours.
Current GEFS prognostics indicate a general shift in the current jet stream position in the general end of the two week period. While it is long range, we can note the shift of the PV to the north along with a +PNA regime. Also some blocking can be noted south of Greenland. While slightly displaced, any blocking helps at this point.
The map above looks encouraging, but issues remain in regards to blocking and the MJO forcing. In fact looking at the wavelengths, it would appear the troughing over the east is transient in nature. The step down pattern I have continued to mention will definitely reign as far as the next two weeks. I do not expect to see any sustainable cold and therefore pattern change until at least December 20. I think while the warmest anomalies will certainly be the several day period after Thanksgiving, there will continue to be an up and down temperature pattern through mid to late December. Slowly but surely colder air will penetrate farther south with each cold front. In fact I would expect temperatures to only average a degree or two above normal for December. I cannot rule out though higher anomalies.
This setup does not mean we cannot get any snowfall. In fact I think this active setup will lend itself to several snow chances through December 20. Towards Christmas and beyond, a very wintry pattern may be setting up. Long term analysis of the stratosphere indicates a dramatic stratospheric warming event may be progged towards January. This will allow the AO to drop negative with a surge of arctic air towards the CONUS.
Generally after December 5 or so, snow chances should be on the increase despite lacking a sustained cold weather pattern. The period immediately following Thanksgiving will allow for near record warmth in some areas!
I will post a new weekly weather blog on Tuesday with forecasts for the Thanksgiving storm which will generally be rain for most all areas.
"Local Harrisburg Radar"
(Courtesy of WGAL)
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