July 31, 2011 Brief Update

Throughout the day, major changes have taken place in the forecast for this week both for the area and in the tropics, which have made the update planned for this evening invalid. A full, detailed discussion will be posted tomorrow morning discussing these changes in more details, and a brief summary of these changes has been posted below:

Tomorrow: Strong to potentially thunderstorms are expected tomorrow afternoon and evening. A cold front which was previously expected to be weak and dry has trended stronger with more moisture and better parameters, which will result in a risk of severe weather. Bulk shear is much lower, however, which may limit the intensity and coverage area of tomorrow’s storms, but mid level lapse rates are much more supportive of severe weather.

Storms should affect the area tomorrow afternoon, and while the storms won’t be as intense or anywhere near as widespread as Friday’s storms, scattered storms are expected, and some of these could become strong or severe, producing small hail and gusty winds, with at least a 15% risk of severe weather expected at this time. Tomorrow morning’s update will include a severe weather risk map.

Wednesday: Some models are showing a strong low pressure affecting the area on Wednesday, bringing a risk of strong to severe thunderstorms, others show the low pressure to the south of the area bringing a chilly heavy rain for NYC, and others only show a weak low pressure with isolated storms. The scenario where the storm tracks to the south of the area is less likely at this time, though there is still a good amount of uncertainty regarding which of the two other scenarios verify. Due to high bulk shear, however, should we see a low pressure to the north of the area, there could be a more widespread severe weather outbreak. Tomorrow morning’s update will discuss this in more details.
Tropics: Invest 91L was originally expected to develop today or tomorrow, but throughout the day, it has split and become much less organized. As a result, both the forecast development time frame and the track of 91L have changed. Stay tuned for an update tomorrow morning in the Tropics page for the new forecast for 91L.

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