Winter begins: The first cold blast of the season for the East Coast

Current synopsis and overview:
Winter is fast approaching and I figured that it’s about time to resurrect the blog ahead of the requests for “When is it going to snow and how much?” Now that I have more time, I can write my thoughts out again.
A cold front passed through this morning, around 7AM as evidenced by a wind shift from the South to a Northwest wind at the Ithaca Airport. Temperatures have dropped from a high of 45 in the morning to 39 currently. Over the next week, temperatures will remain well below normal as arctic air pours out of Canada into the Eastern US. We will likely see our first snows during this period. Currently, I am looking at two chances of accumulating snow over the next week.

12z (7am) analysis of fronts and observations (WPC/NOAA)

Wave 1 Thursday into Friday (11/7-11/8)
A weak low pressure system is currently forming along the front which will direct moisture northwards. Precipitation is expected to start as rain but is expected to change over to snow as temperatures drop from the 40s into the low 30s.

The following forecast for this event is done based on the short term models the HRRR and the 3k NAM:
The changeover will first occur at the higher elevations surrounding Ithaca around 3-4 PM. Changeover for the city will probably be delayed for 1-2 hours due to warmer temperatures.
Steady light to moderate snow will end around 8PM tonight as the front passes and the weak wave moves offshore. Expect that very little snow will accumulate due to warm surface temperatures and weak snowfall rates, perhaps a dusting on elevated surfaces.

HRRR model showing rain and snow associated with the cold front and low pressure wave

As the low draws away, colder air will filter in from the NW, resulting in the development of lake effect snow bands. Current model trends suggest that we could receive 1-2 inches of windswept snow during the day. Temperatures will fall into the lower 20s Friday night as the winds lessen.

NAM 3K model forecast for Friday morning into afternoon showing lake effect snow showers

The following forecast is done based on global models:

Arctic front Sunday into Monday (11/10 -11/11)
Sunday night, a weak disturbance will pass to our north as the arctic front makes its way through. Strong southerly winds the Sunday will ensure that temperatures spike above freezing to the mid to upper 40s before dropping again. A few rain or snow showers can be expected with the frontal passage. This front will set the stage for the next potential event.

Wave 2 Tuesday into Wednesday (11/12 -11/13)
Southern stream energy will combine with northern stream energy to for some kind of low pressure  during this time. Although models have been more consistent on the presence of the energy, but are not in agreement on the evolution. The general progression is that after the front swings through, low pressure will ride the front northwards. Southern stream energy will be drawn in and interact with northern stream energy to energize the system. However, how consolidated the storm(s) are is still up in the air. More northern and southern stream interaction, called phasing, will result in a stronger, more consolidated storm that takes a more westerly track. Less phasing results in two more distinct waves of precipitation, one from the northern stream and one from the southern stream.
In the more phasing scenario, tropical moisture from the southern stream system will act to juice up the system, resulting in more precipitation but a stronger and more northerly storm. Depending on the front position, we would be looking at a all snow or rain to snow scenario. This scenario would bring the highest chance of significant snow accumulations over 6in. In this case, only part of the southern stream energy is expected to phase.

In the less phased scenario, the northern stream energy would likely run out ahead of the southern stream. Snow is still possible, but would probably be a light to moderate event similar to the one today. We would likely be too far north for the southern stream system to impact us.

Of course, another option is that all the disturbances wash out and we are left with just a dry frontal passage with lake effect snow. In conclusion,, given that the storm is still 5 days away, there are a multitude of scenarios that could possibly happen. I am currently leaning towards a s less phased solution with moderate (2-6 in) snowfall. In any case, we can probably expect some more lake effect snow showers as temperatures plunge into the teens following the cold front.

Flowers make my day

Haven't posted in a while. Here, have a photo of some succulents in flower in my dorm room.

Irmagerd, don't panic yet

While Harvey was wreaking havoc on Texas, a tropical wave just off the coast of Africa quietly spun into a tropical storm named Irma. The next day, it became a hurricane, and by the end of that day, a major hurricane, the easternmost Major Hurricane to form in August and the 4th easternmost anytime of the year.

Hurricane Irma satellite imagery http://tropic.ssec.wisc.edu/#

Computer models have been hinting that Irma could affect the US since Irma's birth. Although climatologically, such a strong storm so far out is favored to go harmlessly out to sea, Irma's track is unusual, forced west by strong high pressure. It's also the infamous "I" storm, which have been quite damaging in recent years. Of the 16 "I" storms since 2001, 8 of them have been retired. Interestingly, Irma was selected to replace Irene, which impacted the East Coast in 2011. Storms are retired when the reuse of the name would cause confusion or panic, generally since they have cause major damage.

Retired hurricanes with names staring with "I" since 2001 (Credit: weather.com)

What we know:
Irma is expected to move WSW over the next 3 days as it approaches the Lesser Antilles (beginning of the Caribbean) before beginning a turn to the WNW. All models have the turn happening early enough that Irma will scrape across the northern islands without entering the Caribbean Sea. However, since the sea temps are warmer there, the storm will also get stronger. Right now the National Hurricane Center predicts a Category 4, but a Category 5 hurricane is not out of the question and has been forecasted by nearly every model (including the GFS and ECMWF). As Irma heads west, its direction should turn more northerly, potentially affecting the Bahamas and other landmasses.

Official NHC Forecast issued 11PM EDT, September 2 2017

What is to be seen:
We have little idea about which piece(s) of land will be affected in the longer term. Any potential US landfall is more than a week away, somewhere around September 10th or 11th. Computer models are pretty accurate within 5 days so nailing something 9-10 days away would be an absolute miracle so I'm just going to leave them out for now.  Currently, it seems that the East Coast of the US is going to feel some effect from Irma. Whether it's just a scrape or a full blown landfall is another story.

Either way, it may be wise to review disaster plans and stock up on some essentials such as water and non-perishable foods. Just in case. I will keep you posted.