dallen7908

EPS Percent chances that BWI exceeds 1, 3, 6, and 12" through early next week

EPS BWI

Always best to look at the median

EPS chances of >1, 3, 6, and 12" at BWI through early next week. DCA's EPS has a 78% chance of >1" of snow and similar chances as BWI of >3, 6, or 12. According to the EPS, far northern MD has approximately a 50% chance of >1" of snow and similar chances to DCA and BWI of > 3, 6, and 12".

I get the output from weathermodels.com

Percent of EPS ensembles giving BWI > 1, 3, 6, and 12"

A main purpose of the off hour Euro runs is to provide boundary and initial conditions for regional models used by member states.

http://theweathercentre.blogspot.com/2012/10/east-based-v-west-based-negative-nao.html

"Starting with the 00Z 19 December cycle, the FV3-GFS uses GFDL microphysics instead of the Zhao-Carr microphysics in the GFS." Saw this in the information (i) section of the FV3-GFS comparison site. Is this referring to 2018 or 2017?

EPS Percent Chances of BWI exceeding 1, 3 6, and 12" of snow/sleet through early next week

EPS Probabilities for >1, 3, 6, and 12" of snow/sleet for Baltimore

UKMET precipitation at 144

CPC outlook for December 15 to 28 issued this past Friday (Dan Collins lead forecaster) "Temperature forecasts from the ECMWF, CFS and JMA model consensus, as well as the SubX MME, predict likely above normal temperatures along the Pacific coast of the CONUS, and from the Pacific Northwest across the Great Plains into the eastern U.S., more consistent with statistical forecasts that consider El Nino conditions. " This does not scream "extended big warmup" but we should have our fair share of days in the upper 40s and low 50s.

Rollercoaster ride continues: Percent of EPS ensembles that give Baltimore (BWI?) at least 1, 3, 6, and 12" of snow/sleet through early next week

Baltimore MD EPS Chances of >1,3,6, and 12" of snow through next weekend's possible storm

EPS chances for >1, 3, 6, and 12" of snow at Baltimore through next weekend's possible storm

Percent of EPS ensembles giving Baltimore more than 1, 3, 6, and 12 inches of snow/sleet during the next 10 days from time listed on the left >1” >3” >6” >“12” Dec 01 12UT 68 48 34 10 Dec 01 00 UT 42 28 22 2 Nov 30 12 UT 56 46 16 0 Nov 30 00 UT 44 26 0 0 Nov 29 12 UT 34 16 0 0

Man that H is in a hurry to move out; 1035H north of Bermuda as precipitation reaches DC;

Cold perhaps but none of the 51 EURO ensembles give "us" as much as 3" of snow total during the next 15 days. One or two give us an inch. The GEFS mean snow fall during this period is a bit over an inch. The good news is 15 days will bring us to the 10th when climatology is a weaker enemy.

Another encouraging point is that the bias between the forecast and observed NAO has been near zero since the beginning of November. Last winter the forecast NAO had a low bias of 0.5 to 1.0 units at the 10-14 day time frame.

Alexey Karpechko gave a talk on SSW predictability. He found that last year's event was hinted at 12-13 days out, predicted by 30% of ensembles 11 days out, predicted by 100% of ensembles 4 days out. Here is the abstract from a recent paper by him. The skill of the Arctic stratospheric retrospective ensemble forecasts (hindcasts) of the European Centre for Medium-Range Weather Forecasts extended-range system is analyzed with a focus on the predictability of the major sudden stratospheric warmings (SSWs) during the period 1993–2016. Thirteen SSWs took place during this period. It is found that forecasts initialized 10–15 days before the SSWs show worse skill in the stratosphere than forecasts initialized during normal conditions in terms of root-mean-square errors but not in terms of anomaly correlation. Using the spread of ensemble members to estimate forecasted SSW probability, it is shown that some SSWs can be predicted with high (>0.9) probability at lead times of 12–13 days if a difference of 3 days between actual and forecasted SSW is allowed. Focusing on SSWs with significant impacts on the tropospheric circulation, on average, the forecasted SSW probability is found to increase from nearly 0 at 1-month lead time to 0.3 at day 13 before SSW, and then rapidly increases to nearly 1 at day 7. The period between days 8 and 12 is when most of the SSWs are predicted, with a probability of 0.5–0.9, which is considerably larger than the observed SSW occurrence frequency. Therefore, this period can be thought of as an estimate of the SSW predictability limit in this system. Indications that the predictability limit for some SSWs may be longer than 2 weeks are also found; however, this result is inconclusive and more studies are needed to understand when and why such long predictability is possible.

Random notes From a talk by Amy Butler of NOAA Impacts of SSW extend to 60 days in the troposphere ... with the biggest impacts downstream of North American jet ... cold anomalies midlatitudes/Switzerland ... warm anomalies eastern Canada, sub-tropics Downward coupling does not occur after all SSW ... and that SSW occur in context of other forcings such as ENSO, MJO Phase .. SSW forecasts exceeding 15 days have no skill Week 3/4 skill is much larger when models are initialized with a weak polar vortex. Stronger more organized MJO when the 50 hPA QBP index is easterly

Which is more likely, another December like this one or another February like last one? My hunch is that February 2015's weather was less abnormal but haven't run the statistics. Thoughts?

Remember Ian's article about how uncommon 1" and above snows are becoming at DCA. Well in today's Washington Post there is a non-technical article by Reid Wilson on California's drought that speculates that melting of Arctic ice may be 'contributing to a slowing of the jet stream contributing to colder wetter weather in the eastern U.S. and more persistently dry conditions in the west". I guess for every winner there is a loser. Kind of reminds me of spring 2010, when several hopeful posters here speculated that 2009/2010 could become the new norm or last winter when several scientific articles predicted that melting of Arctic ice could be responsible for warmer eastern U.S. winters and colder European winters.