Thursday, February 2, 2012
Feb 2, 2012: Will Winter Ever Come This Year?
- Partly/mostly cloudy Sunday; storm likely stays south
- Mild start to next week, colder ending possible
- Storm potential between February 10 and 16
The latest radar above shows no precipitation across the entire region, as a weak storm from this morning left the region by the late afternoon after having produced light rain in the southern and central Mid Atlantic, with parts of southern Pennsylvania even reporting sleet mixing with the rain. The stretch of unseasonably mild temperatures will continue straight through the middle of next week, with a weak storm most likely staying to the south of the area this weekend, although a temporary pattern change that has been discussed as a potential recently is increasingly likely to develop towards the second half of next week, bringing what may be the best and perhaps the only opportunity left for the region to see a widespread snow event this winter.
Unseasonably mild temperatures will continue through tomorrow as well, with high temperatures expected to peak in the lower to mid 40s inland and the mid 40s across the rest of the area along with mostly sunny skies. These temperatures are approximately 5-10 degrees warmer than average.
Weekend Outlook: Slightly Cooler, Storm Stays South
Mostly sunny skies are expected to continue through Saturday with temperatures similar to those of Friday. By Sunday, a storm is likely to reach the region, but is more likely to stay to the south of the area. The blizzard that will affect Colorado into Nebraska over the next day will slowly begin to move east as a cutoff low, but will be unable to completely phase with the northern stream over the region at the same time. The result will be a suppressed storm most likely staying to the south of the area. Some of today's afternoon models brought light snow into the area, such as the CMC and NOGAPS, while the GFS and NAM are going with a much further south scenario. While I expect the NAM and GFS to trend further north to bring precipitation at least into southern and/or central New Jersey, it is unlikely at least based on the latest data that the area sees precipitation, with a more likely scenario bringing mostly cloudy skies. A scenario that needs to be watched, however, is where more phasing takes place and light snow makes it up to the NYC area. Right now this is a less likely scenario and is less likely to verify, but it will be watched in case probability decreases or increases. High temperatures will again end up in the lower to mid 40s for Sunday. Stay tuned for more information on Sunday's outlook.
Next Week - Next Weekend: Colder Pattern Temporarily Develops
Until this point, there have been several attempts by the model guidance to bring a pattern change to the region supporting more cold and snow; these potentials have been shown originally for December, then early January, with the most recent one in mid January. Although the pattern did temporarily change for a few days in the middle of January, the changes were unable to sustain themselves and the pattern quickly retreated back to where it has been until now. Although my outlook from January 14 for a warmer pattern redeveloping was off by a couple of days and was a bit too short, the pattern change has failed to sustain itself, and a warmer pattern has redeveloped as expected for the last two weeks. This time, however, there are much more solid signals that while any changes won't be sustained, there are temporary changes coming to the pattern.
Some of the biggest issues this winter regarding why the cold and snow never came involve the stubborn polar vortex near Alaska and the lack of any blocking near Greenland, two important factors that are needed for sustained cold and snow in the East. Without the support of these variables, it is very difficult to get snow events for the area and cold usually is not sustained. Alaska has seen the most winter-like weather across North America, although the true winter conditions are locked up on the other side of the globe; extreme cold and snow are affecting places that typically do not see winter weather this extreme, with cold and snow taking place down to the Mediterranean and even in parts of northern Africa. Around the middle of January, the Alaskan PV was temporarily displaced, which brought down some more cold air towards Canada, although the PV quickly returned, bringing the pattern back to where it has been until then.. In this case, however, there is already a much stronger model consensus that starting from the 84 hour range, the Alaskan PV will be displaced for a longer period of time, with stronger ridging developing near the western US, an important factor needed for a better East Coast trough potential. These changes are far from an ideal cold/snow pattern, as there is still no blocking near Greenland, and the MJO is in phase 7 which is not very supportive of cold and snow, unlike phase 8 which is unlikely to be reached for a long period of time, if at all, although they are more supportive of cold and potentially snow than what the region has seen so far.
With the above considered, a colder ending to next week is likely; while temperatures may not be below average, temperatures are more likely to end up closer to average. With the temporarily colder pattern, there could also be a storm potential; the GEFS mean has been hinting at a storm potential around February 10-13 for the last few days, with the 12z GEFS for hour 216 posted to the left, from the Pennsylvania State University E-Wall (direct link to GEFS maps), clearly showing this potential with strong ridging near the western US and above average 500mb height anomalies through Greenland and into the polar regions, leaving the polar vortex displaced further south near southern Canada at the same time that the set up appears to be indicative of a phase near the eastern US. The GEFS is currently the most bullish with such a potential, and the GEFS has a history of exaggerating pattern changes over the last 2 months, although the other models show the temporarily colder pattern as well. While it is not a guarantee that the area sees snow in the middle of February, the pattern has the best potential of producing such an event between February 10 and 16. It is just as possible that trends repeat themselves and no storm forms, leaving the area with cold and dry conditions before the pattern may trend warmer again after this time frame, but if a storm is to take advantage of the slightly more favorable conditions and produce snow for parts of the region, possibly including the area, this time frame would be when this could happen. This post is titled "Will Winter Ever Come This Year?"; to conclude the discussion, winter in terms of prolonged cold and snow will not come to the area this year. However, a few time frames over the next month and a half, especially around the middle of February, could give the area a taste of what winter is actually supposed to be like.
Posted by NYC Weather at 11:06 PM