January 2014 Archives - Page 2 of 5 - New York Metro Weather

Transition to colder, snowier pattern becoming likely

January 16, 2014/0 Comments/by John Homenuk

Forecast models in the medium to long range,continue to show a pattern change throughout the northern hemisphere — characterized by a west coast ridge and a large, anomalous trough in the Eastern United States. This has been mentioned several times over the last week as our forecasters have suggested the pattern change by the end of January. Exactly how the pattern plays out remains a mystery at this juncture, especially as some continue to overanalyze and interpret operational model guidance — which is never smart. The individual nuances of the pattern are going to take days to iron out.

The first development of note is that the ECMWF has finally caved to the GFS and GEFS interpretation of tropical forcing which will increase later this week and help the development of some major pattern changes. The ECMWF had previously been very stubborn in insisting against this development and keeping the impulse quite week. This cave is very important for the eventual changes in the Pacific including the development of a +PNA regime (i.e the west coast ridge).

MJO forecast from the ECMWF model.

Dense fog takes over NYC, in photos

January 15, 2014/1 Comment/by John Homenuk

The story of the morning, undoubtedly, was the development of dense fog which initially began in only patchy areas of the suburbs early this morning. But by sunrise the fog had lowered and thickened, in addition to spreading throughout the area — including into lower manhattan. The sunrise and aforementioned development of dense, low fog created a terrific (and somewhat rare) picture opportunity as the tops of building and bridges stuck out of the low cloud deck.

Often misunderstood, fog forms as water vapor condenses into tiny water droplets in the lower levels of the atmosphere. Fog is not water vapor itself (Water vapor cannot be seen), nor is it “smog”, a variation of the word which is used to describe lowered visibilities that occur as a result of pollution. But this morning was a more classic case of low fog, more typical in London or San Francisco. The occurrence was a terrific photo opportunity for some of New York City’s best photographers (and webcams). We’ve included some of the best shots below.

The National Weather Service continues a Dense Fog Advisory through noon today, and also urges caution for those who are traveling. Visibilities near zero are possible in some areas, and the fog is expected to cause delays not only on the roads but also at the area airports. The fog is expected to lift by this afternoon, with a chance of scattered showers and high temperatures generally in the mid to upper 40’s.

NYC in fog this morning. Image via Earthcam, twitter.

SPC set to add two new risk categories in 2014

January 14, 2014/0 Comments/by John Homenuk

The Storm Prediction Center has used the same risk categories for a large part of most of our meteorological careers. Although they have adjusted the probabilities, percentages, and yes even the colors — the categorical risk areas have remained the same. In Spring 2014, that will change. The Storm Prediction Center currently uses a simple categorical risk system which highlights the potential for severe thunderstorms across the country. The risk areas of Slight, Moderate and High are triggered by percentage chance of a type of severe weather within 25 miles of any point. And while the newer outlooks also highlight the potential for general non-severe thunderstorms across the country, Spring 2014 will mark a dramatic change in the outlooks.

The main change will be the addition of two risk levels, both falling on opposite sides of the “Slight” risk of severe thunderstorms. “Marginal”, a new risk category, will highlight the potential for severe thunderstorms that includes a 5-10″ chance of wind and hail and a 2-5% chance of tornadoes — but does not trigger a slight risk. “Enhanced” falls on the other side of “Slight”; in other words the risk levels are enhanced (30-45% risk) but not organized or widespread enough to trigger a Moderate Risk. Below, the Storm Prediction Center has released a new probability to categorical description table to help understand the changes.

The new SPC risk categories expected to be implemented in 2014.

Chances for cold and snow are significantly increasing to close the month

January 14, 2014/1 Comment/by Doug Simonian

As we are currently in the midst of a January thaw, many people are looking ahead to find out when this thaw will end and when snow chances will begin. Some rumors had been spreading about a snowfall event on Wednesday/Thursday, and again around Saturday, but both of these threats appear unlikely to produce much in the way of snow. It is not until next week and beyond when we expect the pattern to become more favorable for snow.

Taking look at the threat, or lack-there-of, for Wednesday into Thursday, the main problems stem from a progressive pattern and one that is still in flux.

Today’s 12z European model shows an unfavorable look for a snowstorm on Wednesday night with a very progressive pattern. Image credit goes to the WSI Model Lab.

The above image is the 500mb pattern and vorticity that is forecast by the European model for Wednesday night. There is a large area of vorticity in the southeast states, but notice how it is very elongated and not consolidated. Also notice how there is another disturbance right on its heels in the Northern Plains and Midwest. This leads to shortwave ridging in the Ohio and Tennessee Valley, which penetrates the trough and forces it to be very narrow and progressive. Also working against the potential for a bigger system is the lack Atlantic blocking to help the pattern to buckle. Instead, the entire country has a NW to SE axis to the heights, instead of a more meridional north to south flow. Thus, there is no room for the trough to grow and amplify. So this disturbance slides out to sea, and does not impact the area. There may not be any precipitation at all in the Wednesday night into Thursday time period.

The same general theme holds true for the threat on Saturday.

Today’s 12z European Model valid for Friday night shows a slightly improved pattern for snowfall, but still not one that ultimately supports a snow event. Image credit goes to the WSI Model Lab.

Moving forward to Friday night, we can notice a few important features. First of all, there is still a strong PNA ridge out west, which promotes a tough in the East, and could theoretically favor snowstorm chances. That being said, the Atlantic and Arctic blocking are still nowhere to be found, so the trough cannot buckle. It’s still a progressive pattern — one with a NW to SE height orientation throughout most of the country, which leaves no room for major trough amplification. We have a trough in the East, but once again, the vorticity is relatively disjointed and the trough is being pushed eastward. There is another disturbance right on its heels again in Minnesota, which forces weak shortwave ridging in Illinois, further preventing major amplification of any trough. By the time the trough is finally able to amplify and consolidate, it is already out to sea, with maybe a few passing snow showers. Eastern New England could potentially receive a couple of inches of snow, however.

Tag Archive for: January 2014

Posts