Tropical Weather

Tropical Update: That Escalated Quickly

Hurricane Dorian continues to blast Grand Bahama Island this afternoon, but elsewhere, the Atlantic is getting active quickly.

As of early Tuesday afternoon, Hurricane Dorian was centered about 65 miles north of Freeport, Grand Bahama Island. Dorian is no longer stationary, but it’s not exactly racing along, drifting toward the northwest at 5 mph. After peaking as a Category 5 on Sunday, Dorian has weakened to a Category 2 hurricane this afternoon, with maximum sustained winds near 110 mph. The eyewall has finally moved away from Grand Bahama Island, so continues will slowly improve today.

Dorian’s eye shows up rather nicely on radar from Florida this afternoon. Loop provided by the College of DuPage.

At it’s peak, Dorian had sustained winds of 185 mph, which is tied for the 2nd highest on record in the Atlantic Basin, and the highest for a storm that far north. Only Hurricane Allen in 1980 was stronger, with top winds near 190 mph. Dorian’s lowest pressure of 910mb, is tied for the 9th lowest on record in the Atlantic. It is the strongest hurricane ever to make landfall in the Bahamas.

As for Dorian’s future, the thinking really hasn’t changed much in the past few days. The slow northwestward motion has started, and a turn more toward the north with some acceleration is expected later today and Wednesday as a trough of low pressure approaches the East Coast. This should keep the center of the storm 75 miles or so off the Florida coastline. The outer bands of Dorian will continue to impact coastal Florida, with bouts of heavy rain and gusty winds at times. A Hurricane Warning remains in effect from central Florida up into parts of South Carolina.

Model forecasts for the track of Hurricane Dorian. Image provided by Tropical Tidbits.

To the north, Dorian should start to turn northeastward later Wednesday into Thursday, coming very close to the coastline of both South and North Carolina. This will bring hurricane conditions to these states, and a Hurricane Watch has been issued. Although the official forecast from the National Hurricane Center keeps the center offshore, it will be close enough that even a slight wobble to the left could result in landfall. Whether it makes landfall or not, strong winds, torrential rainfall and very rough surf are expected in these areas over the next couple of days.

GFS model forecast for rainfall across the Southeast through Friday. Image provided by Weathermodels.com

Once past the Carolinas, Dorian should continue northeast, and start to transition into an extratropical storm. That doesn’t mean that it’s done impacting land though. It could graze Cape Cod and the islands with some rain and gusty winds late Friday into early Saturday, but over the weekend it will likely have a significant impact on Atlantic Canada. Heavy rain is likely across parts of Nova Scotia, New Brunswick, Prince Edward Island, and into Newfoundland. While some locations could pick up 2-4 inches of rain, the biggest impact will be from the wind. Sustained winds of 30-50 mph are expected with gusts of 60-70 mph or more, especially along the coastline.

Peak wind gusts expected across Atlantic Canada through Sunday evening according to the GFS. Image provided by WeatherBell.

Dorian isn’t the only active storm in the Atlantic any more. Tropical Storm Fernand formed this afternoon in the Gulf of Mexico. As of early Tuesday afternoon, it was centered about 160 miles east of La Pesca, Mexico, moving toward the west at 7 mph. It has maximum sustained winds near 40 mph, and is expected to strengthen a little more over the next 24 hours. A Tropical Storm Warning has been issues for parts of northeastern Mexico. The system will likely make landfall late Wednesday, with the biggest impact likely to be from heavy rainfall. Rainfall totals of 6-12 inches and locally heavier will produce flooding and mudslides across the area. Heavy rain is expected across parts of South Texas, where 2-4 inches may fall, resulting in some flash flooding.

Forecast track for Tropical Storm Fernand. Image provided by the National Hurricane Center.

But wait, there’s more! There are two other systems in the Atlantic that are being monitored this afternoon. The stronger of the two is a few hundred miles west of the Cape Verde Islands. This system will likely become a tropical depression later today or tonight. It should turn more towards the northwest and stay harmlessly out at sea for the next several days likely not impacting any land areas at all.

Model forecasts for the track of a tropical disturbance in the eastern Atlantic. Image provided by Tropical Tidbits.

Another disturbance is located several hundred miles south of Bermuda this afternoon. This system is not well-organized, and conditions aren’t very favorable for further development. It will be monitored over the next few days, and may bring some squally weather to Bermuda later this week.

Satellite loop of the Atlantic showing TD7 on the left edge of the screen, Dorian near the Bahamas, a disturbance south of Bermuda, and another disturbance in the eastern Atlantic. Loop provided by NOAA.

If that’s not enough, there’s another wave still over western Africa that will move into the Atlantic later this week. Forecast models are showing the potential for that wave to develop as well. This shouldn’t be a big surprise, September is the peak of hurricane season. This is just the Atlantic – we didn’t even get into the Pacific, where Hurricane Juliette is a Category 3 Hurricane southwest of Mexico, Typhoon Lingling is passing east of Japan on its way towards Korea, Tropical Storm 14W is expected to become a typhoon passing north of the Northern Mariana Islands on its way towards Japan, and Tropical Depression Kajiki is making landfall along the coast of Vietnam.

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Tropical Weather, Weekly Outlook

Weekly Outlook: September 2-8, 2019

Believe it or not, there is weather besides Dorian taking place right now, and some of it will impact us. Oh Dorian may at some point as well, but we’ll get to that.

The week starts off with a cold front approaching from the west. If you’ve got outdoor plans for Labor Day, you should be OK through at least midday. Although we’ll have plenty of clouds around, the showers and thunderstorms we’re expecting should hold off until the afternoon. Some of these showers and storms could produce some heavy rainfall, especially during the late afternoon and evening hours.

The front pushes offshore, with showers ending overnight, then high pressure builds in for Tuesday with mild and drier conditions. The high shifts offshore on Wednesday, allowing warmer and more humid air to move back in. Temperatures should be well into the 80s, and a few places could even get to 90. However, another cold front will move through late in the day, with some additional showers likely. Behind that front, much cooler air settles in on Thursday with high pressure building back in.

Temperatures should get well into the 80s on Wednesday. Image provided by WeatherBell.

This brings us to the Dorian part of the forecast. If Dorian is to have any impact up here, it will be in the Friday/Saturday time frame. Dorian will produce some rough surf along the coastline, but beyond that, we’re not sure if there will be any other impacts. A lot will be determined by the track that Dorian takes, but it should pass well south and east of New England. Whether it’s still a hurricane, a tropical storm, or even an extratropical storm, is too tough to predict this far out. Some of the models have it pass close enough to bring in some heavy rain and gusty winds, especially to Cape Cod and Southeastern Massachusetts. Some of the local TV meteorologists were already hyping this up on the 11pm news Sunday night. Sure, it’s possible that this could happen. It’s also possible that the storm stays far enough offshore to have little to no impact on us beyond the rough surf. For now, we’re going to play the middle ground on the forecast, but obviously, we’ll be doing some special blog updates on Dorian during the week, as it’s future becomes more clear.

Most of the forecast models keep Dorian well south and east of New England, for now. Image provided by Tropical Tidbits.

High pressure will be building into the Northeast for the end of the week and the weekend. If Dorian stays too far offshore, it will be dry and cool around here for Friday through Sunday. If Dorian does have some impact, it’ll just be dry and cool on Sunday behind the storm.

Labor Day: Mostly cloudy with showers and thunderstorms likely in the afternoon. Some of the storms may produce heavy rainfall. High 70-77.

Monday night: Showers and thunderstorms ending, followed by clearing late at night. Low 56-63.

Tuesday: Clouds may linger across Cape Cod in the morning, otherwise partly to mostly sunny. High 74-81.

Tuesday night: Clear to partly cloudy. Low 58-65.

Wednesday: Becoming partly to mostly cloudy, breezy, and humid, with showers and thunderstorms likely during the afternoon. High 80-87.

Thursday: Sunshine filtered through increasing high clouds streaming northward from Dorian. High 67-74.

Friday: Partly to mostly cloudy, breezy, and cool with a chance of rain, especially south of Boston. High 63-70.

Saturday: Breezy with a chance of rain early, then becoming partly to mostly sunny. High 69-76.

Sunday: A mix of sun and clouds. High 67-74.

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Tropical Weather

Hurricane Dorian Prepares to Assault the Bahamas

Earlier this week, the models were showing the potential for Hurricane Dorian to smash into Florida and the hype train left the station at full speed. Well, now that the models have shifted, the hype train is on a different track. Dorian is now expected to smash the Northwestern Bahamas on Sunday before heading towards the Southeastern United States.

Dorian is not going to be a welcome visitor to Freeport Harbour on Sunday.

As of 11pm Saturday, Dorian was centered about 125 miles east of Great Abaco Island in the Bahamas, moving toward the west at 8 mph. Maximum sustained winds are near 150 mph, making Dorian a Category 4 Hurricane on the Saffir-Simpson Scale. Hurricane Warnings been been issued for the Northwestern Bahamas except for Andros Island, which is under a Hurricane Watch. A Tropical Storm Watch has been issued for the east coast of Florida, from Deerfield Beach to Sebastian Inlet.

Satellite loop showing Hurricane Dorian east of the Bahamas. Loop provided by the College of DuPage.

Dorian’s immediate future is fairly clear – it will continue westward overnight and into Sunday, passing very close to Freeport in the Bahamas as a powerful hurricane. Rainfall totals to 10-20 inches or more along with a storm surge of 10-15 feet will result in flooding along the coast and across the interior of the islands. While some additional strengthening is possible, some fluctuations are also possible as Dorian will likely start to undergo an eyewall replacement cycle at some point in the next 12-24 hours. The eyewall is where the strongest winds and most intense rainfall of a system are located. In an eyewall replacement cycle, the eyewall starts to collapse, and a new one forms a little farther away from the eye. This new eyewall eventually contracts closer to the eye, but in the meantime, it allows a storm to weaken. These are nearly impossible to predict, but they do occur in most hurricanes, mainly intense ones.

It’s pretty easy to see Dorian’s eye on radar this evening. Image provided by the Bahamas Meteorology Department.

After Dorian moves through the Bahamas, things get very tricky. Dorian is currently being steered westward by a ridge of high pressure located to its north. As a trough of low pressure moves into the Tennessee Valley, it will erode that western edge of that ridge, leaving Dorian in an area with little flow to steer it. It may stall out or move very little late Sunday and Sunday night, which is bad news for the Bahamas, as much of the circulation may remain over the northwestern Bahamas, resulting in catastrophic damage for parts of the region. If Dorian stays in the same place long enough, it may bring cooler water up to the surface in a process known as upwelling. Hurricanes need warm water to help fuel them, so sitting over cooler water could help Dorian to weaken a bit.

Computer model forecasts for the track of Hurricane Dorian. Image provided by Tropical Tidbits.

After that, as the ridge continues to erode and the trough advances eastward, a turn toward the north and eventually northeast is expected. Exactly when this turn occurs is still a rather large question mark. While the majority of the forecast models show this turn occurring offshore, not all of them do. This is mostly good news for Florida, as it would likely keep the worst effects offshore, though gusty winds, some rainfall, and rough surf are still likely along the coast. How far inland the rain and wind penetrate will be determined by the eventual track.

The HWRF model still shows landfall near Cape Canaveral. While a Florida landfall looks unlikely at this point, there is still a chance it can occur.

This is bad news for portions of the Southeast, especially coastal portions of the Carolinas. A track close to the coastline in these areas seems a bit more probable at this point, which means, strong winds, heavy rainfall, and rough surf are likely for a prolong period during the middle of the upcoming week. Although the forecasts are for the center of the storm to remain offshore, it would not take much of a deviation for the center to make landfall, which would increase the threat for damaging winds and storm surge.

GFS model forecast for rainfall through Friday. Image provided by WeatherBell

After forming last weekend, Dorian crosses Barbados and Saint Lucia as a tropical storm last Monday night. After reorganizing a little to the north, it then passes just east of St. Croix in the US Virgin Islands on Wednesday strengthening into a hurricane as it moved across St. Thomas, where it produced sustained winds as high as 82 mph with a gust to 111 mph.

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Tropical Weather

The Tropics Are Starting to Get Active

It’s been a very quiet hurricane season so far, not just in the Atlantic, but in the Pacific as well, but that appears to be changing.

It’s been a quiet season compared to normal across the Atlantic and Pacific this far. Image provided by Colorado State University.

The most immediate concern is Tropical Storm Dorian. As of 2pm Monday, Dorian was centered about 95 miles east-southeast of Barbados, and was moving towards the west-northwest at 14 mph. Dorian has maximum sustained winds near 60 mph, and additional strengthen is expected. Tropical Storm Watches and Warnings are in effect for much of the Lesser Antilles, and a Hurricane Watch is in effect for St. Lucia.

Tropical Storm Dorian is approaching the Lesser Antilles. Loop provided by NOAA.

Dorian is expected to pass very close to Barbados this evening, and then close to St. Lucia or St. Vincent overnight tonight or early Tuesday. Because Dorian is not that large, the worst effects (damaging winds, torrential rainfall) will likely be limited to these islands.

Model forecasts for the track of Tropical Storm Dorian. Image provided by Tropical Tidbits.

Once Dorian moves past the Lesser Antilles, the questions become tougher to answer. The official forecast from the National Hurricane Center calls for Dorian to become a hurricane and turn northwestward, passing close to western Puerto Rico on Wednesday and then eastern portions of Dominican Republic Wednesday night and early Thursday, with some weakening as it interacts with land. In terms of the track itself, most of the forecast models are clustered in this area, give or take 100 miles. The intensity forecast is the biggest question mark for now. The Hurricane Center is calling for the storm to have maximum sustained winds of 80 mph when it reaches Puerto Rico and Hispaniola. However, looking at the various models, they are showing that it could be as strong as a Category 3 system, or as weak as a tropical depression. Intensity forecasts are still the toughest part of forecasting tropical systems, and for a small storm that has dry air all around it, this one is especially tough. Frankly, at this point, we wouldn’t be surprised with any outcome.

Model forecasts for the intensity of Tropical Storm Dorian. Image provided by Tropical Tidbits.

What about when it gets beyond Hispaniola and Puerto Rico? The official track and the various models all show the storm heading into the Bahamas and possibly towards Florida or the Southeast. It is still WAY too early to speculate on that (but that won’t stop the hype machine from Twitter and the Facebook Forecasters). First, we need to see if Dorian even survives that long. The mountains in central Hispaniola rise as high as 10,000 feet. Many storms that cross this area get torn apart by the terrain and dissipate. If (and that’s a big “if”) it survives, we’ll have to see what kind of shape it’s in when it emerges into the Bahamas before we can assess it’s future. This is all presuming the storm turns northwestward and heads towards Puerto Rico and Hispaniola. There’s nothing that says it won’t continue westward and heads towards Cuba or Jamaica. Just because none of the computer models are forecasting it does not mean it can’t happen.

Meanwhile, off the East Coast, a low pressure system is developing about 300 miles southeast of Cape Hatteras, NC this afternoon. This system could become a tropical or subtropical storm later today or tomorrow. As we mentioned in our Weekly Outlook, while the system is expected to stay well offshore and not impact the East Coast, this is far from definite. Some of the forecast models this afternoon show some moisture from the system interacting with an approaching cold front to bring some rain into parts of eastern New England Wednesday night and Thursday. Obviously, this will depend on exactly where the system tracks.

Model forecasts for the track of a developing system off the East Coast. Image provided by the University of Wisconsin.

Whether or not the system has any impact on New England, it will likely bring some gusty winds and heavy rain to portions of Atlantic Canada toward the end of this week. Rainfall totals of 2-4 inches and locally heavier are possible along with winds gusts to 50 mph along the coast, possibly higher, depending on how strong the storm gets. While this seems like an average Nor’easter, it will come on the heels of a non-tropical system that will bring heavy rain and strong winds to the same area tonight into Wednesday. Not exactly an ideal ending to summer for parts of the region.

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Heavy Rain/Snow, Tropical Weather

Trouble Brewing in the Gulf

It’s been a fairly slow start to hurricane season in the Atlantic, which is fairly normal, but things are starting to heat up in the Gulf of Mexico.

A disturbance dropped southward from the Tennessee Valley over the weekend, moving into the Gulf of Mexico on Tuesday. With plenty of warm water and only a little wind shear, the system is starting to get organized this afternoon, and could become a tropical depression later today or on Thursday.

Thunderstorm activity is getting more organized in the northern Gulf of Mexico this afternoon. Loop provided by NOAA.

As of 2pm Wednesday, the system was centered about 155 miles east-southeast of the mouth of the Mississippi River, moving toward the west-southwest at 8 mph. It is producing sustained winds of 30 mph, with some higher gusts. Steady strengthening is expected for the next few days. A Tropical Storm Watch has been posted from the Mouth of the Mississippi River to Morgan City, Louisiana. A Storm Surge Watch has also been posted from Pearl River to Morgan City.

Forecast tracks for Potential Tropical Cyclone Two from various forecast models. Image provided by WeatherBell.

The forecast models are fairly unanimous that the system will continue westward for the next 36-48 hours, but after that point things become unclear. A turn toward the northwest and eventually north is expected as an upper-level trough moves into the Great Plains, but when that turn occurs has a very significant impact on the system. A quicker turn means that the storm spends less time over the warm waters of the Gulf, and thus has less time to strengthen. A later turn means the opposite, more time over water, more time to strengthen, and the greater likelihood of it becoming a hurricane. Intensity forecasts are notoriously poor to begin with, and this system is no different. Very few models are predicting the system to reach hurricane strength, but the National Hurricane Center’s official forecast does call for the system to become a hurricane before landfall. As we mentioned already, the eventual track of the system will play a large part in determining this.

Intensity forecasts from various models for Potential Tropical Cyclone Two. Image provided by the University of Wisconsin.

Storm surge is a danger with any storm system, and this one is no different. Storm surge of 2-4 feet is likely near where the center makes landfall. Since much of southern Louisiana is already low-lying, this could result in flooding for much of the region. Wind damage will also be a concern across the region, which again will be dependent on the strength of the system. Winds will pick up Friday night across portions of Louisiana and possibly eastern Texas, with landfall most likely on Saturday right now, but this is obviously subject to change.

Rainfall forecast for the Gulf Coast for the next 6 days. Image provided by Weathermodels.com

By far, the biggest threat with this system will be rainfall. Tropical systems produce copious amounts of rainfall, and this one will be no different. Rainfall totals of 6 to 12 inches are expected across parts of the Gulf Coast, with some amounts to 20 inches possible. This would produce widespread flooding across the region, but in this case, it will just exacerbate existing flooding problems. The Mississippi River remains above flood stage across the region, and this will only worsen the flooding. On top of that, thunderstorms dropped up to 10 inches of rain on parts of New Orleans Wednesday morning, and that’s before the precipitation from the system even reaches the area. The Mississippi River is expected to crest in New Orleans at a level of 20 feet, which is also the same height that the levee system protects the city to. Obviously this will bear watching. Upstream, the River has been above “Major Flood” stage in Baton Rouge since February 26. It’s not likely to drop below flood stage until at least some time in August, if then.

River forecast for the Mississippi River at New Orleans. Record flooding is not expected, but the levee system will likely be tested once again. Image provided by NOAA.

Elsewhere, the Atlantic remains quiet, with no other systems expected to develop in the next week or so.

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Extreme Temperatures, Heavy Rain/Snow, Severe Weather, Tropical Weather, Winter Weather

Hurricanes, Severe Weather, and Snow, All at the Same Time (not the Same Place)

For the third year in a row, the “M” storm in the Atlantic is prepared to wreak havoc on a populated area, but Michael isn’t the only headline maker in the weather at the moment.

Hurricane Michael isn’t the only storm in the news, but it is the biggest threat at the moment. As of early Tuesday afternoon, Michael was centered about 335 miles south of Panama City, Florida, moving toward the north at 12 mph. Maximum sustained winds are near 110 mph, making Michael a Category 2 Hurricane. Additional strengthening is expected over the next 12-18 hours as the storm moves over the warm waters of the eastern Gulf of Mexico. Hurricane and Storm Surge Warnings are in effect for the Florida Panhandle and the Big Bend area of Florida, with Tropical Storm Warnings and Watches surrounding the Hurricane Warnings. Tropical Storm Watches are also in effect for the Atlantic coast from northeastern Florida into South Carolina.

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Michael is going to pack quite a wallop when it slams into the Florida Panhandle Wednesday afternoon. Image provided by the National Hurricane Center.

Michael is expected to make landfall in the Florida Panhandle Wednesday afternoon, likely as a Category 3 storm. Strong winds, torrential rainfall, storm surge, and some tornadoes are all possible with this storm. Unlike Florence, which hung around the Carolinas for days and dumped incredible amounts of rainfall on the region, Michael is expected to keep moving at a steady pace, emerging off the Mid-Atlantic coast by Friday morning. Rainfall totals of 5-10 inches are still expected in parts of the region, which will produce flooding in some areas, especially in Carolinas, where many areas are still recovering from Florence. Right along the coast, a storm surge of 6-12 feet is possible, especially in the Big Bend area of Florida. Fortunately, this area is not heavily populated, but for the residents that do live in this area, storm surge flooding is a significant threat.

Once it moves back into the Atlantic early Friday, it should pass well south of our area. The northern edge of the rainfall from the system could reach the South Coast, but the bulk of the heavy rain should remain well to the south.

This is the 3rd year in a row that the “M” storm is expected to result in significant damage to a populated area. In 2014, Category 5 Hurricane Matthew left a path of death and destruction across parts of Haiti, Cuba, the Bahamas, and eventually parts of the southeastern United States. Last year, Category 5 Hurricane Maria devastated the northeastern Caribbean, including Puerto Rico and the US Virgin Islands. While Michael is not expected to become a Category 5 storm, it is still expected to result in significant damage to parts of Florida and the Southeast.

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Tropical Storm Leslie has been around for near 2 weeks and still looks rather healthy. Loop provided by NOAA.

Meanwhile, in the eastern Atlantic, Tropical Storm Leslie refuses to go away. As of midday Tuesday, Leslie was centered a little more than 1000 miles west-southwest of the Azores, moving toward the south-southeast at 13 mph. Maximum sustained winds are near 65 mph. The forecast for Leslie calls for a turn more toward the east over the next few days while it strengthens back into a hurricane. Leslie is expected to remain over open waters for the next few days, and could become an extratropical storm this weekend while continuing on a general easterly track.

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Nadine is a fish storm. Nothing to worry about here. Image provided by Tropical Tidbits.

To the south, Tropical Storm Nadine as formed nearly 500 miles southwest of the Cabo Verde Islands. Nadine has maximum sustained winds near 40 mph, and is moving toward the west-northwest at 9 mph. Nadine is expected to remain fairly weak over open waters for the next several days while turning more toward the northwest. As it moves over colder water late this week and this weekend, it should weaken and eventually dissipate.

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What month is it again? 70s and 80s early in the afternoon on October 9th? Image provided by WeatherBell.

Back in the United States, unseasonably warm conditions remain in place across much of the eastern half of the nation. Temperatures are in the 70s and 80s across much of the region, which is 15 to 25 degrees above normal. A strong frontal system is located in the Plains states this afternoon, separating the warm air in the East, from much cooler weather behind it in the Plains and the Rockies. Right along this front, which hasn’t moved much for the past 24 hours, severe weather and heavy rainfall are common this afternoon.

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That’s snow in Colorado, and heavy rain along with severe weather from Texas into the Central Plains this afternoon. Loop provided by WeatherTAP.

Several tornadoes have been reported already today, including a few in the Oklahoma City area, and more are expected later today and tonight. Heavy rainfall is also expected from Texas into the Central Plains and parts of the Upper Midwest. Rainfall totals of 1-3 inches and locally heavier may produce flash flooding in some areas. Flash flood watches are in effect for much of the region.

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Several inches of snow is expected form the Plains into the Upper Midwest over the next few days. Image provided by Pivotal Weather.

On the other side of the front, where much cooler weather is in place, rain is expected to change over to snow as low pressure rides along the front and into the Midwest. Winter weather advisories have already been posted for parts of the region. Snow is already falling in parts of Colorado this afternoon, and several inches may fall over the next 36-48 hours from western portions of Kansas and Nebraska into the Dakotas and northern Minnesota.

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Some heavy rain is possible across our area on Thursday as a strong cold front approaches the region. Image provided by WeatherBell.

As the system moves eastward, it will spread some heavy rain and thunderstorms into our area on Thursday. We’re not expecting any severe weather, but some heavy downpours are possible, especially from western Massachusetts into southern New Hampshire. Some localized flooding may result. Once this front pushes offshore, much cooler weather will settle in for the Friday and the weekend.

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Tropical Weather

Tropical Update: Subtle Changes

Since our last blog post about the tropics yesterday, we’ve had some subtle, but important changes with most of the systems we’re watching.

As of early Wednesday afternoon, Hurricane Florence was centered about 485 miles southeast of Wilmington, North Carolina, moving toward the northwest at 15 mph. Maximum sustained winds are near 130 mph, making Florence a Category 3 Hurricane. Florence may strengthen a bit today as it moves over the warmer waters of the Gulf Stream while continuing on a northwestward track. Once it gets close to the coastline is where things start to get complicated.

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GFS forecast for the track of Hurricane Florence. Loop provided by Tropical Tidbits.

The upper-level steering currents will collapse as the storm nears the coastline, which will cause the storm to slow down, and perhaps even stall out. Many of the models show this stall, followed by a slow drift toward the southwest. Exactly where it stalls is somewhat important. If the storm makes landfall, and then stalls out over southern North Carolina, it will quickly weaken, lessening the wind impact, but prolonging the heavy rainfall. If the storm stalls while the center is still offshore, it will weaken more slowly as it slowly churns up the warm water it is sitting over, but this will prolong the wind and storm surge impacts along the coast.

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Tremendous amounts of rain are still expected in the Carolinas, leading to catastrophic flooding. Image provided by Weathermodels.com

These changes are actually a bit of good news for some areas, and bad news for others. This shift in track will significantly lessen the impact and amount of rainfall expected across the Mid-Atlantic states and even northern parts of North Carolina. While heavy rain is still expected, rainfall totals of 2-4 inches and locally heavier will not cause as much flooding as 6-12 inches of rain would. To the south, this is bad news – really bad news. The impact of rain, wind, and storm surge will be prolonged across southern North Carolina, and now will extend into a large portion of South Carolina. If the southwest trend in the track were to continue even longer, as a few models of shown, these impacts could even spread into parts of Georgia.

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Model forecasts for the track of Tropical Storm Isaac. Image provided by Weathermodels.com

To the south, Tropical Storm Isaac is looking even weaker today, and the threat to parts of the Caribbean is diminishing. As of early Wednesday afternoon, Isaac was centered about 420 miles east of Martinique, moving toward the west at 17 mph. Maximum sustained winds have decreased to near 60 mph. Westerly shear has been impacting Isaac since Tuesday afternoon and is starting to rip the system apart. Since this shear is not expected to relax for another day or two. Tropical Storm Watches and Warnings are in effect for much of the Lesser Antilles. Isaac should cross the islands early on Thursday, bringing heavy rain and gusty winds to the region. However, the system should continue to weaken, and could degenerate into an open wave as it moves into the eastern Caribbean. It will still bring some heavy rain into Puerto Rico and the Virgin Islands, but won’t have anywhere near the impact of last year;s powerful storms. Some of the forecast models show the potential for the system to regenerate and strength as it moves into the western Caribbean this weekend, so even if the system does become an open wave in the next day or two, we’ll still keep an eye on its progress as it heads westward.

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Model forecasts for the track of Hurricane Helene. Image provided by the University of Wisconsin.

As for Hurricane Helene, not much has changed. As of midday Wednesday, Helene was centered about 1350 miles south-southwest of the Azores, moving toward the north-northwest at 14 mph. Maximum sustained winds remain near 90 mph. Helene is expected to continue northward, steadily weakening while move over cooler waters. The current forecast calls for Helene to pass very close to or over the Azores this weekend as a tropical storm. Heavy rain and gusty winds would be the main threats to the Azores. The system should lose tropical characteristics over the weekend, but may impact parts of the British Isles as a strong extratropical system early next week.

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A disturbance in the Gulf of Mexico could become a tropical depression in the next 24-36 hours. Loop provided by NOAA.

Meanwhile, an area of disturbed weather is slowly getting organized in the Gulf of Mexico. If this trend continues, the system could become a tropical depression tonight or Thursday. It should continue on a west to west-northwest track, heading towards Texas. The main threat with this system will be heavy rains across portions of southeastern Texas, likely leading to flooding in some areas.

Another disturbance is developing several hundred miles west of the Azores. Conditions are favorable for more development and this system could also become a tropical storm in the next day or so. This system will likely remain over open waters for the next several days, and is not a threat to any land areas right now.

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Radar loop showing Tropical Storm Olivia approaching Hawaii. Loop provided by NOAA.

In the Pacific, Tropical Storm Olivia is gradually weakening while approaching the Hawaiian Islands. As of Wednesday morning, Olivia was centered about 140 miles east of Honolulu, moving toward the west at 12 mph. Maximum sustained winds have decreased to near 45 mph, and some additional weakening is expected. Tropical Storm Warnings remain in effect for Oahu and Maui County. Olivia will continue to bring heavy rain and gusty winds to the islands today. Rainfall totals of 5-10 inches and locally heavier will produce flooding in some areas. Once past the islands, Olivia should continue westward, likely dissipating over the open waters of the Central Pacific later this week.

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Tropical Storm Barijat is passing south of Hong Kong. Loop provided by NOAA.

In the western Pacific, Tropical Storm Barijat remains fairly weak. As of midday Wednesday, Barijat was centered a little more than 100 miles south-southwest of Hong Kong, moving toward the west at 10 mph. Maximum sustained winds were near 45 mph, and Barijat is expected to slowly weaken while continuing westward, likely making landfall in southern China over the next 12-18 hours. Heavy rain may lead to flooding across portions of southern China and northern Vietnam before the system dissipates.

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Super Typhoon Mangkhut will become an increasing threat to the Philippines later this week. Image provided by the Joint Typhoon Warning Center.

Meanwhile Super Typhoon Mangkhut remains a beast of a storm this afternoon. As of midday Wednesday, Mangkhut was centered about 870 miles east of Manila, moving toward the west at 14 mph. Maximum sustained winds are near 170 mph, making Mangkhut the strongest storm on the planet so far this year. Mangkhut has likely peaked in intensity, and a slow weakening trend is expected over the next few days. As for Mangkhut’s future, the forecast track has shifted a bit to the south since yesterday. This will now bring the center of the storm close to or over northern portions of Luzon, the largest of the islands in the Philippines. The northern tip of the island is somewhat rural, with hilly terrain, which means the storm wouldn’t affect as many people, but it will still be at or close to Super Typhoon intensity at the time, so a major impact is still expected. After that, a track into the South China Sea is still expected, with some additional weakening likely before a final landfall late this weekend  early next week in the same vicinity of where Barijat is expected to make landfall today or tomorrow.

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