John Homenuk

The meteorology behind Hurricane Sandy’s very low pressure

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Nearly three years since Hurricane Sandy, many of her visual scars have faded. The memories of the storm, for many, have not. Meteorologically, Sandy remains just as incredible now as she was then — an unbelievable display of atmospheric power. One of the most fascinating aspects of Sandy was how strong she was, despite entering cooler waters. The meteorology behind her pressure is powerful and intricate, still, three years later.

Hurricanes have a strong warm core at the surface, weaken with height, and are barotropic — meaning there are no temperature or density gradients in their environment. This means that they are symmetric — their warm core is entirely surrounded by slightly cooler, but still abundantly warm air. The combination leads to hurricanes being vertically stacked (not tilted with height). Thus, hurricanes need warm water and weak upper-level winds in order to strengthen. Strong upper-level winds can choke a hurricane’s outflow channel, and advect in new airmasses of different temperatures — providing temperature gradients that hinder their development.

In further south latitudes, waters tend to be warmer, and the jet stream tends to be weak. As you head further north, however, the water becomes colder and the jet stream strengthens, leading to stronger upper-level winds. This helps to weaken a hurricane’s warm core at the surface, and tilt its vertically stacked structure, weakening the storm. However, as Sandy headed north, she was able to maintain category one hurricane strength with abnormally low pressures and eventually went on to cause widespread devastation. Why?

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John Homenuk

Midweek storm system likely to bring widespread rainfall

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It has been quite some time since our area experienced an area-wide moderate rainfall event. That looks to change during the middle of this coming week, as the remnants of Hurricane Patricia interact with another atmospheric dsiturbance over the Central United States. The resulting low pressure system will develop through the Great Lakes and into Canada, allowing the northward surge of moisture along the East Coast and toward our area on Wednesday.

Interestingly enough, the indirect impacts from Patricia will be enough to bust a pattern which had been continuously dry in our area. Moderate drought conditions continued in much of Northern New Jersey, NYC, Long Island and Connecticut to start this week, still lingering from the very dry summer months. New York City is still running 8″ behind the average seasonal rainfall total. This weeks rainfall event, then, may be “welcomed”.

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John Homenuk

Clearing out late Sunday, cooler to start the week

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Showers, clouds, and dreary conditions were widespread on Sunday morning as a cold front and associated moisture slowly made its way through the forecast area. The moisture and atmospheric forcing for precipitation will shift east of the area by early this afternoon, and as it does so, drier air will begin to filter into the area. This will help skies clear out during the afternoon hours. Mid level atmospheric temperatures will also still remain “warm”, with the coldest air lagging behind the cold fronts precipitation from this morning. So high temperatures on Sunday afternoon may actually be quite pleasant.

Colder air will begin to filter in to the area by Sunday Night into Monday morning, as mid and upper level atmospheric temperatures drop as well. With northerly winds taking over on Monday, high temperatures will struggle into the middle 50’s during the afternoon hours. It will feel quite brisk compared to the past few days, even with abundant sunshine expected. While the cooler temperatures are expected to continue through the early part of the work week, some moderation in temperatures is expected by Tuesday and Wednesday.

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John Homenuk

Here’s how to see archived model runs of historic storms

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The Blizzard of 2006 was a tremendous snowstorm in our local area. While it did fall in the middle of a warm and otherwise uneventful winter, it featured some tremendous dynamics and impressive banding. Do you remember what forecast models were showing prior to that event? Me neither. Up until now, it’s been fairly difficult to find archived model images dating back to the mid 2000’s, and even if you accessed them, the images were coarse and the graphics difficult to comprehend.

That has changed. Unknown to some, there is an easy and simple way to  access model data from the wildly popular free model data website at Penn State University. Known as “Ewall” to meteorologists and hobbyists alike, this website has been around for many years, and has served as a central hub for model data while remaining “new” to the times with upgrades and new graphics. The website also houses a freely accessible archive of model images dating back to 2004.

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