June 29, 2011 Brief Update

4:40 PM: The next full update will be posted early tomorrow morning, however there are some changes with the latest forecast which will be discussed in more details with tomorrow morning’s update, which will include an updated 5-Day Forecast. The latest models have trended towards a direction in which the trough currently over the region fails to exit; it remains stuck just off the coast and even intensifies next weekend, almost completely blocking the ridge from moving into the area and instead bringing a single warm day with upper 80s followed by lower 80s with clouds and rain chances. The main models showing this are the GGEM and ECMWF, and the NAM’s latest 18z run trended towards this scenario as well. The GFS still does not show this, but it has been trending towards this solution with its last 6 runs, and may begin to trend colder by tonight’s 18z/00z runs.

Should the originally expected scenario verify, which is still a possibilty but not a very likely one, temperatures would reach the upper 80s to lower 90s across the area on Saturday, with Sunday the hottest day with temperatures potentially reaching the mid 90s in the immediate NYC area, followed by upper 80s to lower 90s persisting through Wednesday with occasional thunderstorm chances. We are still under a negative NAO and positive PNA pattern with no significant pattern change expected through early July, however, and especially considering the pattern we’ve been under so far this year, there is some reason to doubt such a long lasting major heat spell. While today’s scenario on the models is only a very recent change, it may very well be more likely than the original prolonged heat wave solution, as the pattern this year seems to be repeating itself over again with long range heat potentials that turn into slightly below average temperatures along with rain chances. Tomorrow’s update will discuss this potential change in the forecast in more details.

Tropics: Tropical Storm Arlene, the first named storm of the Atlantic hurricane season, formed last night from Invest 95L, which was mentioned in yesterday’s afternoon update. Arlene is currently a moderate tropical storm, with 50 mph sustained winds and a minimum pressure of about 1000 mb. While Arelene likely does not have enough time to intensify into a hurricane prior to landfall tonight, it is expected to peak as a strong tropical storm, with sustained winds between 60-70 mph, when it makes landfall in Mexico. Other than Arlene, there is no tropical disturbance that may develop into a tropical cyclone over the next few days.

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