Tropical Storm Helene has strengthened during the past 24 hours and is on the verge of attaining “category 1” hurricane status with sustained winds of 74-95 mph. All indications are that Helene will undergo rapid intensification during the next 24 hours or so given the combination of favorable environmental conditions such as low vertical wind shear and ample moisture, and its movement over very warm water with high oceanic heat content. This expected intensification of Helene will likely result in attainment of “major” hurricane classification on Thursday as a category 3 storm system with sustained winds of 111 mph – 129 mph. Helene should begin to accelerate tomorrow in a north-to-northeast direction likely resulting in a landfall early tomorrow night along Florida’s “Big Bend” Gulf coastal region. As is typical of northward moving tropical storms, the storm surge should be most impactful to the right of the landfall location potentially affecting coastal sections down to areas just north of Tampa Bay. In addition, there will be the threat of tornadoes to the right of the storm’s track including portions of northern and eastern Florida, Georgia and South Carolina.
After landfall, the remnants of the hurricane will move along at a pretty good clip in a general northward direction through the state of Georgia where there is likely to be significant impact including hurricane-force wind gusts and excessive rainfall amounts. In fact, excessive rainfall may extend to throughout much of the southern Appalachians where strong upsloping winds will enhance upward motion and increase overall amounts. By mid-day on Friday, the tropical system will become increasingly influenced by very strong “blocking” high pressure to the north and an upper-level trough of low pressure located in the southern Mississippi Valley. The tropical low will “rotate around” this upper-level trough of low pressure for a brief time in a pattern known to meteorologists as the “Fujiwhara effect” before it ultimately dissipates and gets absorbed by the upper-level low.
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A strong tropical wave continues to churn over the warm waters of the western Caribbean Sea and it is likely to threaten Florida’s Gulf coast as a “major” hurricane by late Thursday. This system should attain named tropical storm status shortly (minimum winds of 39 mph) and then it should take a track in between the Yucatan Peninsula of Mexico and the western tip of Cuba as it heads to the southern Gulf of Mexico. Intensification will then continue as it heads on a general northward track over the warm waters of the eastern Gulf and it could climb to “major” hurricane classification (i.e., category 3 or higher) before a likely landfall late Thursday somewhere near Florida’s “Big Bend” Gulf coast region.
After landfall, the remnants of the hurricane will push in a general northward direction through Georgia and South Carolina producing powerful wind gusts and significant rainfall along the way. At this point, the tropical system will become increasingly influenced by very strong “blocking” high pressure to the north and an upper-level trough of low pressure dropping southeastward into the south-central states. In fact, the tropical low may “rotate around” this incoming upper-level trough of low pressure for a brief time in a pattern known to meteorologists as the “Fujiwhara effect” before it ultimately gets absorbed by the upper-level low..
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A strong tropical wave has developed over the northwestern Caribbean Sea during the past day or so and it is likely to threaten Florida’s Gulf coast as a hurricane later in the week...potentially a “major” hurricane of category 3 classification or higher. A significant change to the overall large-scale weather pattern in the Atlantic Basin is now underway and it is much more conducive to the formation and intensification of tropical systems. This change is the result of a re-positioning of a tropical disturbance known as the “Madden-Julian Oscillation” and it is leading to enhanced upward motion over the Caribbean Sea and Gulf of Mexico. This more favorable weather pattern for tropical cyclone activity will likely last well into the month of October. In the near-term, all residents from New Orleans to Tampa should continue to monitor this current threat closely over the next couple of days.
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The atmosphere is about to undergo a significant change over the Caribbean Sea and Gulf of Mexico which will result in enhanced upward motion in that part of the Atlantic Basin and this, in turn, increases the chance for the development of a hurricane later next week. The change in the atmosphere is largely the result of the re-positioning of a tropical disturbance that propagates eastward along the tropics on a regular basis. This undergoing pattern change with enhanced upward motion in the Atlantic Basin may, in fact, result in additional tropical activity that takes us passed this initial threat and well into the month of October.
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Hurricane Francine is closing in on the central Louisiana coastline as a strong category 1 storm and maximum sustained winds of around 90 mph. After landfall later today, Francine will slowly weaken as it pushes in a general northeasterly direction reaching southern Mississippi by early Thursday. From there, the remnants of Francine will become increasingly influenced by very strong high pressure ridging over southern Canada and its northward progression will grind to a halt over the western part of the Tennessee Valley. With the atmospheric blocking still in place later this weekend, new low pressure is likely to form somewhere near the Carolina coastline. This system will have plenty of available tropical moisture and its rain field could push slowly to the north early next week…potentially bringing some beneficial rains to the Mid-Atlantic region.
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After a lengthy quiet period in the Atlantic Basin with no named tropical storms, Francine was born this morning over the southwestern Gulf of Mexico and it is likely to threaten the Louisiana coastline on Wednesday as a hurricane. A tropical wave that has been meandering over the warm waters of the SW Gulf in recent days has now attained named tropical storm status and it is likely to strengthen into a hurricane on Tuesday and then head towards the Louisiana coastline for a possible landfall later in the day on Wednesday. Francine is expected to bring heavy rainfall and the risk of flash flooding all the way from coastal sections of far northeast Mexico to southern Mississippi and an increasing likelihood of storm surge inundation.
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The climatological peak of the Atlantic Basin tropical season is just around the corner and there are now as many as five systems to monitor in coming days after a very lengthy quiet period. In fact, there has not been a newly named tropical storm in the Atlantic Basin since “Ernesto” first reached that designation on August 12th, and this is the longest such quiet stretch since the late 1960’s. With five separate tropical systems currently showing some life in the Atlantic Basin and near-term changes coming to the overall weather pattern, the absence of named tropical storms is very likely to soon come to an end.
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The month of September is now underway and there are three tropical waves to monitor in the Atlantic Basin in coming days, but none of these has yet to attain named tropical storm status. In fact, there has not been a newly named tropical storm system in the Atlantic Basin since “Ernesto” formed back on August 12th. The time period from the 13th of August until today, September 3rd, is the first such quiet stretch since 1968 without a newly named tropical system.
At the same time the tropics are showing some life after a quiet stretch here in early September, cool, crisp and dry air is dominating the scene from the Great Lakes/Upper Midwest to the Mid-Atlantic/Northeast US. Numerous locations early this morning were quite close to their record low temperatures for the date and indeed, there were a few spots that actually set daily low temperature records.
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The month of August will likely end up with very close-to-normal temperatures in much of the Mid-Atlantic region and Northeast US and it looks like September will get off to cool start. Indeed, a cool blast of air will push into the Upper Midwest and Great Lakes region later this weekend and then arrive in the Mid-Atlantic region and Northeast US on Monday, Labor Day following the passage of a couple of cold frontal systems. The initial cold front this weekend will likely result in numerous showers and thunderstorms later Saturday and Saturday night across the northeastern states and then a secondary cold front can produce some shower activity on Sunday and Sunday night. By Monday and Tuesday, highs will be confined to the 70’s across the Mid-Atlantic/NE US and overall humidity will be at very comfortable levels.
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A taste of fall is coming to the Mid-Atlantic region for the Tuesday, Wednesday, and Thursday time period following the passage of a cold front later today. That frontal system will produce scattered showers and thunderstorms this afternoon and evening and some of the storms can be on the strong side. Temperatures for the next few days should peak in the 70’s for afternoon highs all along the DC-to-Philly-to-NYC corridor which is well below-normal for this time of year. Temperatures in the overnight hours will bottom in the lower 50’s in much of the I-95 corridor – coolest so far this season – and some spots could bottom out in the upper 40’s well to the northwest of the big cities.
Elsewhere, Ernesto has intensified slightly during the morning hours over the North Atlantic with latest observations showing 90 mph maximum sustained winds. This classifies Ernesto as a strong category 1 hurricane which is somewhat unusual in that it weakened to tropical storm status on Sunday after passing by the island of Bermuda. Ernesto will rush past Newfoundland later tonight and then it can very well impact Ireland/United Kingdom later in the week as an extratropical storm.
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