The climatological peak of the Atlantic Basin tropical season comes in mid-September and this year is certainly holding true to form. Tropical Storm Gordon came ashore overnight in the vicinity of the Alabama/Mississippi border region and is now well inland over the central part of Mississippi. While Gordon has been downgraded to tropical depression status, it is likely to contribute to an extended swath of heavy rainfall in coming days. Meanwhile, Florence has intensified into major hurricane (category 3) status out over the central Atlantic. There is still a chance that Florence gets “captured” by an eastward-moving upper-level trough of low pressure this weekend over the north Atlantic, but odds favor it being “left behind”. If indeed Florence is not “captured” by the trough this weekend then strong and expanding high pressure ridging to the north early next week could very well steer it westward towards the US east coast. Any potential impact on the US east coast by Hurricane Florence would likely come during the middle or latter part of next week.
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The climatological peak of the Atlantic Basin tropical season comes in mid-September and this year is certainly holding true to form. There are currently three tropical systems to monitor and other systems are likely to form in coming days. Tropical Storm Gordon is heading towards the Mississippi/Louisiana border region and is likely to make landfall there late tonight. Florence has just reached hurricane status and it is moving on a WNW track out over the open central Atlantic. There is a chance that Florence gets "captured" by a eastward-moving trough this weekend; however, if it is left behind then the evolving pattern could become quite threatening for the US east coast. Yet another system trails Florence relatively close to Africa’s west coast and it will also likely become a concern in coming days.
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The climatological peak of the Atlantic Basin tropical season is around the middle of September and it certainly looks like there will be a ramp up in activity after a relatively quiet month of August. In fact, there very well may be a burst of activity with potentially several named storms over the next 2 or 3 weeks taking us right into the middle of September. Two areas of interest currently exist and the "front-runner" of these two systems could actually have an impact on Florida and the Gulf of Mexico by the early-to-middle part of next week. The second system is still not far off of Africa's west coast and it will have to be closely monitored given the expected strong high pressure ridging next week across the Northeast US and southeastern Canada.
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The Pacific Ocean is the planet’s biggest and its sea surface temperature (SST) pattern has a tremendous influence on all weather and climate around the world. In particular, El Nino conditions (warmer-than-normal) in the equatorial part of the Pacific Ocean can have a tremendous impact on winter weather in the US depending on its intensity and duration. In addition to duration and intensity, the specific location of an El Nino in the equatorial Pacific Ocean can be quite crucial to wintertime temperatures and precipitation patterns in the US and current signs point to a weak-to-moderate strength El Nino that is “central-based” and this raises the prospects for a cold and snowy winter in the eastern US.
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Hurricane Lane weakened some in the past 24 hours as it has encountered increased southwesterly wind shear, but it remains a “major” category 4 storm as it slowly closes in on the Hawaiian Islands from the south. There is still a good chance that Hurricane Lane will not make actual landfall on any of the island chain; however, it'll still generate tremendous amounts of rainfall on parts of the state and some sections can experience hurricane conditions (e.g., Maui, Oahu). The fact that it is a slow mover and will come close to the island chain will allow for a prolonged period of torrential rainfall, especially, on windward facing slopes with up to two or three feet possible on the Big Island. This is very likely not going to be the last tropical threat for Hawaii this season as warmer-than-normal sea surface temperatures and a developing El Nino in the central Pacific Ocean will likely aid in the formation of additional systems in coming days.
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In general, the Pacific Ocean has had more tropical activity this season compared to the Atlantic Basin and that trend should continue in the near term. Sea surface temperatures are playing a role in this trend and they are currently warmer-than-normal in the vicinity of Hawaii with a major hurricane headed in that direction. Fortunately, Hurricane Lane is likely to not make a direct hit on the islands and it should undergo steady weakening in coming days due to increasing amounts of wind shear. Nonetheless, Hurricane Lane will be a formidable storm for the state of Hawaii with potential significant impact in terms of rainfall; especially, on the Big Island. This is very likely not going to be the last tropical threat for Hawaii this season as warmer-than-normal sea surface temperatures and a developing El Nino in the central Pacific Ocean will likely aid in the formation of additional systems in coming days.
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It has been a very wet summer in much of the Northeast US/Mid-Atlantic and significant rain is likely to fall in many areas over the next several days. In fact, I think the chances are quite high that some spots see several inches of new rainfall between late today and the middle of next week and this will fall on already well-saturated grounds. A slow-moving cool frontal system will only grudgingly move across the area over the next 48 hours and this will result in numerous rounds of showers and thunderstorms beginning late today and lasting well into the upcoming weekend. This will make it the 10th weekend of the past 13 with some rainfall in at least parts of the Northeast US/Mid-Atlantic. Another front will approach the area late Tuesday and it’ll be supported by a vigorous upper-level energy which is likely to result in more downpours come late Tuesday/early Wednesday.
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The Atlantic Basin has been relatively quiet in recent days in terms of tropical activity and it continues to look like this will be a less active tropical season compared to 2017. One of the main factors that led us to an outlook for a less active tropical season back in the springtime was the large patch of colder-than-normal water at that time in the eastern Atlantic Ocean. This continues to exist and is quite likely an inhibiting factor for the formation or intensification of tropical activity in the tropical Atlantic and there are a couple other factors as well that are likely deterring activity. First, Saharan Desert (dry) air has persistently flowed westward from western Africa and into the tropical Atlantic and there are signs that this general pattern will continue into at least the near future. In addition, wind shear has been quite prominent across the tropical Atlantic in recent days and there are reasons to believe that this will continue to impede tropical activity in coming weeks. Don’t let your guard down; however, as all it takes is a direct hit by one storm to make it a memorable tropical season.
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A strong cool front is closing in on the I-95 corridor and strong-to-severe thunderstorms are popping over the past couple of hours. Daytime heating is contributing to increasing instability in the atmosphere and the coverage and intensity of shower and thunderstorm activity should increase through the afternoon hours. Any storm that forms over the next several hours can produce brief downpours, damaging gusty winds and even some hail. There is also the potential for some steadier and heavier rain this evening; especially, in areas north of the PA/MD border.
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A low pressure system will form later today along the Delmarva/New Jersey coastal region and it will result in more downpours, gusty winds and perhaps even a period of steady, heavy rain for much of the I-95 corridor. In recent days, the axis of heaviest rainfall has extended from the Chesapeake Bay/DC metro region to central Pennsylvania, but this coastal low pressure system will bring some heavy rainfall to places farther east such as New Jersey and New York City.
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