John Homenuk

Labor Day weekend begins with sun

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Low clouds and fog burned off and broke up this morning, and the sun made an appearance shortly after noon in New York City. A weak disturbance sliding east/southeast off the coasts of New Jersey and Long Island was the culprit for the morning clouds, but the backdoor cold front which hampered Thursdays weather has weakened and washed out this afternoon. Winds will flip from east-northeast to west-southwest, helping to keep temperatures a bit on the warmer side today especially in areas that get more sun. Highs in the mid 80’s look to be a common theme. Pleasant weather is expected through tonight, with lows in the 60’s to lower 70’s.

Visible satellite imagery and regional observations from the afternoon of August 30th, 2013.

Visible satellite imagery and regional observations from the afternoon of August 30th, 2013.

The Labor Day Weekend forecast is not as straight forward, however, as multiple perturbations in the mid level flow will cause unsettled weather in the area beginning on Saturday. High temperatures will reach into the mid to upper 80’s on both Saturday and Sunday, but thunderstorms look to become more likely as the weekend draws on. The storms should be relegated to the western suburbs on Saturday, but may become more widespread on Sunday. We aren’t looking at a threat for widespread heavy rain, but any storm could certainly put a hamper on outdoor activities.

A frontal system comes through on Monday with a low pressure passing north of the area — with showers and storms likely from Sunday night into Monday. As it stands now, Saturday looks like the winner of the weekend..with warm temperatures and good beach weather, despite the chance of scattered storms. Stay tuned for more details and have a wonderful Friday!

John Homenuk

PM Update: Clouds break, unsettled trend continues

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Mostly cloudy skies, including the presence of drizzle and some fog, hampered the forecast for the majority of Thursday. Although temperatures still reached into the 70’s and near 80 with humidity on the rise, the sun was absent — a poor beach day for those who are still clinging to the last few available this summer. The humidity and mugginess in the air may have left Thursday feeling somewhat uncomfortable. A weak disturbance will pass through the area overnight tonight, and with a backdoor cold front in the area a few storms are possible over the far interior suburbs and Northwest PA. Generally, however, dry conditions are expected through the majority of the area this evening. Low temperatures are expected to fall into the 60’s throughout most of the area tonight.

Water Vapor satellite imagery and observations from 6pm on 8/29/13

Water Vapor satellite imagery and observations from 6pm on 8/29/13

The backdoor front will wash out a bit by Friday, and with the easterly flow (which caused the clouds/fog on Thursday) weakening and backing to a south-westerly flow, we are expecting a warmer day with more sun. Highs should top out in the lower 80’s in most areas. The weekend looks to remain unsettled, with a chance of storms each day — fairly difficult to pinpoint, but no threats of widespread heavy rain. Saturday looks like the winner of the weekend, with highs in the 80’s and a chance of storms mainly relegated to the western suburbs. Storm chances increase both Sunday and Monday before a cold front crosses the area.

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Doug Simonian

Arctic Sea Ice Loss Not Nearly as Bad as Last Year

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Global climate change has been a pretty hot topic in the world of meteorology and climatology for quite some time now. Skeptics and pro AGW (Anthropogenic — meaning human as opposed to natural — Global Warming) have raged on and on. One of the main components that people like to look at to track the degree of warming is the amount of Arctic Sea Ice loss. As the calendar slides through August and into September, we get closer and closer to the minimum ice extent for the year, before recovering for the fall and winter. Arctic Sea Ice has really declined in the past several years — potentially due to AGW, as the amount of loss last year was absolutely staggering. In fact, the entire 2007-2012 period saw unprecedentedly low levels of Arctic Sea Ice that led many to become quite worried about this being the new normal.

Most global climate simulations indicate that the area of greatest warming would be in the Arctic — mainly because it is easier to heat something that is cold than what is hot. Decreasing the amount of Arctic Sea Ice could lead to lots of devastating climate feedbacks on the Earth’s system, such as a lot less radiation being deflected back into space, and further yielding warming. This is because ice and snow have a higher albedo (ability to reflect heat radiation back into space) than water. Thus, a warming arctic –> more water and less ice & snow –> lower albedo in the arctic –> less heat radiation is reflected back into space (and is instead absorbed by the water) –> warming arctic. This means that the feedback helps to amplify the original effect of warming the arctic, without increasing the warming effect itself.

When the Artic regions are quite warm, this is obviously bad for many ecosystems alike. But it would also greatly alter the weather patterns in that it would change the jet stream configuration, since if you are warming the Arctic a lot more than the equatorial latitudes, you are decreasing the temperature gradient between the two, which is what fuels the jet stream to begin with. There are a lot more climate feedbacks and such, but to save time, we won’t get into that for now.

Arctic Sea Ice extent from this year (red) is much higher than from last year (black). However, it is still well below the 1979-2006 averages.

Figure 1: Arctic Sea Ice extent from this year (red) is much higher than from last year (black). However, it is still well below the 1979-2006 averages.

Arctic Sea Ice can be measured in two ways: ice extent and ice area. The National Snow and Ice Data Center explains the differences well here, but essentially, the analogy is swiss cheese. Extent would be the distance from the edges of the cheese and all of the space inside the edges — so it does not include the holes, whereas the area takes the holes into account. There are pros and cons to using each method, but the NSIDC uses extent.

The chart above shows the Arctic Sea Ice extent from the past several years, in comparison with the 1979-2006 averages. Obviously, we are still well below the 1979-2006 averages, so it is not time to “cancel” global warming. However, we have had a very significant recovery from this time last year — it is almost two million square kilometers above last year’s level! This is great news. Although we are really only near the 2009 level and not necessarily that deviant from the past several years, the increase is quite significant and a bit unprecedented, since year-to-year increases of this magnitude are rare.

 

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Sun, warmer air return for midweek

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A low pressure system scooting quickly off the coast of Long Island has kept some clouds and showers around early this morning, mainly over New York City and eastward through Long Island. Water vapor satellite imagery (pictured above) shows drier air moving in behind the aforementioned low pressure system, diving southward from New York State and Pennsylvania. The result will be clouds giving way to more sun by this afternoon, as the low pressure moves eastward well off the coast.

In addition to the drier air and northerly wind component this afternoon, warmer temperatures will move in aloft. Forecast models indicate 850hPa temperatures increasing from 12-14c this morning to 15-17c by this evening. High temperatures this afternoon will approach the middle to upper 80’s in many areas, and will be warm even down to the area beaches thanks to the north winds. What starts out as a cloudy day across the east end, will turn into a gem of a Tuesday for the majority of the forecast area. Enjoy!

Today: Partly to mostly cloudy skies will give way to plenty of sun, north winds, and highs in the middle to upper 80’s. A tremendous late-summer Tuesday is on the way. No weather hazards or weather-related travel impacts are expected.T

Tonight: Partly cloudy skies return, and pleasant weather is expected early. However, a few isolated showers cannot be ruled out in the late evening to overnight period. Low temperatures falling into the upper 60’s to lower 70’s.