Category: Tropical Weather

The Atlantic Hurricane Season of 2020 – Where Does It Really Rank?

No doubt for areas of the coast affected by the storms, it was a year reminiscent of recent 2017 and 2005 seasons.

Though we about to tie the record for number of named storms (now at 27 versus 28 in 2005), we are running 152% of normal for the Atlantic Basin ACE (Accumulated Cyclone Energy Index) – very close to 2019 (148%) and 2018 (149%) but running well behind 2017 (252%), 2005 (280%) and 1933 (290%).

Note while the Atlantic was active, the Pacific was quiet and the Northern Hemisphere was just 68.2% of normal.

Image provided by Colorado State University.

See the storm tracks including 10 hurricanes and 4 majors.

Real-Time North Atlantic Ocean Statistics by Storm for 2020

Year Storm# Name Dates TC Active Max Wind (kts) MSLP (mb) Named Storm Days Hurricane Days Major Hurricane Days Accumulated Cyclone Energy
2020 1 ARTHUR 5/17-5/19 50 991 2.50 0.00 0.00 1.8
2020 2 BERTHA 5/27-5/27 45 1007 0.50 0.00 0.00 0.4
2020 3 CRISTOBAL 6/2-6/8 50 992 4.75 0.00 0.00 3.5
2020 4 DOLLY 6/23-6/24 40 1002 1.00 0.00 0.00 0.6
2020 5 EDOUARD 7/6-7/6 40 1005 1.00 0.00 0.00 0.6
2020 6 FAY 7/9-7/11 50 998 1.50 0.00 0.00 1.1
2020 7 GONZALO 7/22-7/25 55 997 3.50 0.00 0.00 2.8
2020 8 HANNA 7/24-7/26 75 973 3.00 0.75 0.00 3.4
2020 9 ISAIAS 7/30-8/4 75 987 6.00 2.25 0.00 9.2
2020 10 JOSEPHINE 8/13-8/16 40 1005 3.00 0.00 0.00 1.8
2020 11 KYLE 8/14-8/16 45 1000 1.50 0.00 0.00 1.0
2020 12 LAURA 8/21-8/28 130 938 6.75 2.25 1.00 12.8
2020 13 MARCO 8/22-8/25 65 991 3.25 0.25 0.00 3.4
2020 14 OMAR 9/2-9/2 35 1003 0.75 0.00 0.00 0.4
2020 15 NANA 9/1-9/3 65 994 2.75 0.25 0.00 2.6
2020 16 PAULETTE 9/7-9/22 90 965 10.25 3.50 0.00 15.9
2020 17 RENE 9/7-9/12 45 1000 4.00 0.00 0.00 2.2
2020 18 SALLY 9/12-9/17 90 967 4.50 2.00 0.00 7.4
2020 19 TEDDY 9/14-9/23 120 945 9.00 7.25 2.75 27.8
2020 20 VICKY 9/14-9/17 45 1000 3.00 0.00 0.00 2.1
2020 21 BETA 9/18-9/22 50 994 4.00 0.00 0.00 3.3
2020 22 WILFRED 9/18-9/20 35 1007 1.75 0.00 0.00 0.9
2020 23 ALPHA 9/18-9/18 45 998 0.50 0.00 0.00 0.4
2020 24 GAMMA 10/3-10/5 60 980 2.75 0.00 0.00 2.5
2020 25 DELTA 10/5-10/10 120 953 5.25 4.25 2.00 15.7
2020 26 EPSILON 10/19-10/25 100 952 6.00 4.50 0.50 12.0
2020 27 ZETA 10/25-10/25 35 1005 0.25 0.00 0.00 0.1

Activity was shown decades ago to relate to the AMO (Atlantic Multidecadal Oscillation) cycle with active seasons favored in the warm decades and quieter ones in cold ones. Likewise when La Ninas are present suppressing eastern Pacific storms which can disrupt upper level winds in the Atlantic, action in the Atlantic is more favored. Both a warm AMO and La Nina are present this year.

See how the number of major hurricanes in the Atlantic tracks with the AMO.

See the last warm period 1950-1969 versus the cold 1970-1987 period.

When the AMO >1 STD, the ACE averages 140.1. When it is more than 1 STD negative, the ACE averages just 49.9.

As noted, the other key is ENSO. El Ninos increase the upper level shear in the Atlantic by favoring much more action in the eastern Pacific. Those storms disturb the upper level flow increasing shear over disturbances trying to develop. In La Ninas like 2020, the shear is less allowing more disturbances to grow to storm status. Indeed when the NINO34 is warm (>1 STD), the ACE averages 109.2 and when more than 1 STD negative (La Nina), it is just 42.4.

AN ATLANTIC THREAT INDEX

If we create an Index of AMO minus the NINO34 STD values we would expect when significantly positive (>1 STD), the Atlantic Basin should be more active and when > 1 STD negative, quiet. See how the ACE tracks well with that index.

On average when the Index is > 1 STD, we have an average ACE of 140.1, when it is more than 1 STD negative, the average is 49.9.

Despite years with more storms, the number of landfalling hurricanes and major hurricanes for the mainland has been declining with the last decade the second quietest since 1950.

Landfalling storms is the best measure of trends as before the satellite era we missed many often short lived storms in the eastern Atlantic. Even in the record ACE season of 1933 (ACE of 258.6 versus 135.2 this season) you can see we probably missed storms.

Make it Five – Five Active Tropical Cyclones in the Atlantic

With the formation of Tropical Storm Vicky this morning, we now have a record-tying five storms in the Atlantic, and there may be another one coming soon.

The most immediate threat to the US is Hurricane Sally. Sally strengthening into a hurricane this afternoon, and should continue to slowly strengthen in the Gulf of Mexico for the next 24 hours. As of early Monday afternoon, Sally was centered about 160 miles southeast of Biloxi, Mississippi, moving toward the west-northwest at 6 mph. Maximum sustained winds have increased to near 90 mph.

Forecast track for Hurricane Sally. Image provided by the National Hurricane Center.

Sally is expected to track across the northern Gulf of Mexico while strengthening later tonight and Tuesday. Current forecasts call a turn to the north on Tuesday, with landfall in either southeastern Louisiana or southern Mississippi on Tuesday. Hurricane and Storm Surge Warnings are in effect for much of the region. The location of landfall will have a significant impact on what conditions occur in some locations, namely storm surge. The highest storm surge is usually found near and to the right of where the center makes landfall. A landfall in southeastern Louisiana brings that storm surge to parts of the Louisiana coast and into Mississippi and Alabama. A track a bit farther east spares Louisiana from significant surge, but increases the threat to Mississippi, Alabama, and parts of the Florida Panhandle.

Significant storm surge is likely near and to the east of where the eye makes landfall.

While storm surge and strong winds are significant threats, rainfall will be the most significant issue residents of the Gulf Coast need to prepare for. Sally will be a slow-mover, and could even stall out near or just after landfall. We’ve seen plenty of slow-moving tropical systems dump torrential rainfall on places in recent years, and this system will likely do the same. Rainfall totals of 15-25 inches and possibly heavier will create widespread significant flooding. The heavy rain will also spread well inland, with flooding possible into parts of the Tennessee Valley later this week.

Torrential rainfall is likely along the Gulf Coast. Image provided by Weathermodels.com.

While Hurricane Sally is a threat to land, Hurricane Paulette impacted land earlier this morning, when it moved directly across the island of Bermuda. Paulette was centered about 115 miles north of Bermuda early this afternoon, moving toward the north-northeast at 13 mph. It has maximum sustained winds near 105 mph, and some additional strengthening is likely over the day or so as it turns more toward the northeast. Paulette is expected to head out into the open Atlantic over the next several days, presenting no additional threat to land.

Radar loop showing Hurricane Paulette approaching Bermuda Sunday night and early Monday. Loop provided by Brian McNoldy, Univ. of Miami, Rosenstiel School

In the central Atlantic, Tropical Depression Rene remains weak late this morning. It is centered about 1100 miles northeast of the Lesser Antilles, and maximum sustained winds have decreased to near 30 mph. Rene is expected to dissipate over open water in the next day or two.

Heading further eastward, we have Tropical Storm Teddy. As of late this morning, Teddy was centered about halfway between the Lesser Antilles and the Cabo Verde Islands. Maximum sustained winds were at 40 mph, and additional strengthening is likely. Teddy could become a hurricane by late Tuesday or Wednesday, and could strengthen into a rather potent storm by later this week. A turn toward the northwest should keep Teddy over open water, though residents of Bermuda should keep an eye on this storm, as it could present a threat to the island by late this weekend or early next week.

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

Even farther to the east, Tropical Storm Vicky developed this morning. As of late morning, Vicky was centered about 350 miles west-northwest of the Cabo Verde Islands, moving toward the northwest at 6 mph. Maximum sustained winds were near 45 mph. Vicky is expected to turn more toward the west over the next day or two while slowly weakening. It will likely dissipate over open water later this week.

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

With the formation of Vicky, we now have five named storms in the Atlantic. This ties the record for the most named storms at once, originally set between September 11-14, 1971. During September 11-12, 1971, there was also a short-lived tropical depression in the Atlantic, so we had 6 active tropical cyclones, a record that still has not been broken.

As if five storms wasn’t enough. Another tropical wave moved off the coast of West Africa today. Conditions may be favorable for some development over the next few days as it heads westward into the Atlantic.

Four Active Systems in the Atlantic, A Fifth May Be on the Way

On average, the peak of hurricane season in the Atlantic is the middle of September. Right on cue, the 2020 season has seen a significant uptick to activity, with four active systems, and possibly a fifth one a few days from now.

There are 4 active systems in the Atlantic at this time. Image provided by the National Hurricane Center.

 

The most immediate threat to the US is Tropical Storm Sally. Tropical Depression 19 formed Friday evening just off the coast of southeastern Florida. The center of the system moved inland Friday night just south of Miami, producing wind gusts of up to 50 mph and heavy rain across south Florida. Early Saturday afternoon, the depression had strengthened into Tropical Storm Sally, and by late afternoon was centered about 30 miles south-southwest of Naples, Florida, moving toward the west at 7 mph. Maximum sustained winds were near 40 mph.

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

 

Sally is expected to track northwestward across the Gulf while strengthening over the weekend. The current forecast has it strengthen into a hurricane by Monday, but conditions could be favorable for it to intensify even faster. Current forecasts call for landfall in either southeastern Louisiana or southern Mississippi late Monday night or early Tuesday. While storm surge and strong winds will obviously be a threat, rainfall will be the most significant issue residents of the Gulf Coast will need to prepare for. Sally will be a slow-mover, and could even stall out near or just after landfall. We’ve seen plenty of slow-moving tropical systems dump torrential rainfall on places in recent years, and this system will likely do the same. Rainfall totals of 10-20 inches and possibly heavier will create widespread significant flooding.

Torrential rainfall will produce flooding across parts of the Gulf Coast early next week. Image provided by Weathermodels.com.

 

Tropical Storm Sally isn’t the only storm that is threatening land at this time. Tropical Storm Paulette is centered about 460 miles southeast of Bermuda this afternoon, moving toward the northwest at 15 mph. It has maximum sustained winds near 70 mph, and it will likely become a hurricane tonight. Additional strengthening is likely over the next couple of days as the storm continues northwestward before turning more toward the north. Unfortunately, that northerly turn will happen right around the time that Paulette reaches Bermuda’s longitude. A hurricane warning has been issued for Bermuda. Current forecasts call for the storm to pass very close to or right over the island late Sunday night and early Monday as a Category 2 hurricane. Paulette will also bring large waves to parts of the East Coast over the next several days, increasing the threat for rip currents at the beaches.

Forecast track for Tropical Storm Paulette. Image provided by the Bermuda Weather Service.

 

Bermuda is no stranger to tropical cyclones, as they are impacted by one per year on average. Last year, Hurricane Humberto produced wind gusts in excess of 120 mph on the island when the center passed just to the northwest. The last hurricane to make landfall in Bermuda was Hurricane Nicole in 2016. The only other storms to move directly across Bermuda in the 30 years before Nicole were Hurricane Fabian in 2003 and Hurricane Emily in 1987. One element of hurricanes that Bermuda doesn’t have to worry about is storm surge. Because the island is essentially a peak in the middle of the ocean, the water doesn’t have time to build up approaching the coast. The reef surrounding the island also helps to disperse some of the water before it reaches land. Humberto was a Category 3 storm that passed just northwest of the island last year, but only produced a storm surge of 2-3 feet. A similar storm impacting the US could produce a storm surge of 10-15 feet on average.

In the eastern Atlantic, Tropical Depression Rene is slowly weakening this afternoon. It is centered about 1200 miles east-northeast of the Lesser Antilles, and maximum sustained winds have decreased to near 35 mph. Rene is expected to remain weak while meandering around in the central Atlantic for the next few days. Conditions won’t be that favorable, and it will likely dissipate over open water by early next week.

Forecast track for Tropical Depression Rene. Image provided by the National Hurricane Center.

 

Even farther to the east, Tropical Depression 20 has developed this afternoon. It is centered a little more than 2000 miles east of the Lesser Antilles, and is moving toward the  west-northwest at 9 mph. Maximum sustained winds are near 35 mph, and additional strengthening is likely. It will likely become a tropical storm on Sunday, at which point it will be named Teddy.  It is expected to continue strengthening while crossing the Atlantic over the next several days. It will not impact any land areas for at least another 5 or 6 days, if at all. Some of the models show the potential for this to become a significant storm, so we’ll keep an eye on it.

Model forecasts for the track of Tropical Depression 20. Image provided by WeatherBell.

 

Another area of disturbed weather is crossing the Cabo Verde Islands this afternoon. It will bring squally conditions to the islands tonight. There is some potential for this system to develop over the next few days as well. Once it moves past the islands, it will likely not be a threat to any land areas, even if it does develop.

September Has it All – Heat, Snow, Drought, and Tropical Storms

Autumn and Spring are the transition seasons, and September is certainly proving that right off the bat.

Intense heat has been common across much of the West for the past few days. Temperatures well over 100 degrees have been common, with numerous records set. One location, Richmond, on the eastern side of San Francisco Bay, reached 107 degrees Monday, afternoon, tying their all-time record, originally set on September 15, 1971. Several other locations set monthly records for September as well. The worst of the heat is over, but it will remain hot on Tuesday, with highs likely topping 100 across much of interior California and the Desert Southwest, possibly setting a few more records.

Another hot day is likely across interior California on Tuesday. Image provided by WeatherBell.

 

Heat was also common across the Plains and Rocky Mountains over the weekend, but big changes are developing thanks to a strong cold front. Denver set a record high of 97 on Sunday, then reached 93 on Monday. On Tuesday, that 93 will get reversed with a high closer to 39. On top of that, accumulating snow is likely. Even by Denver standards, this is quite early in the year for snow. Their all-time record for earliest snow is September 3, 1961, but on average Denver doesn’t see it’s first flakes until October 18. This won’t be the 1st time that Denver hit 90 one day and then had measurable snow the next. On September 12, 1993, Denver recorded a high of 92 degrees, and on September 13, they had 5.4″ of snow.

While a few inches of snow are likely in Denver and onto the adjacent High Plains of eastern Colorado and western Nebraska, heavier snow is likely across the mountains on Colorado and Wyoming. Across the higher elevations, snowfall totals in excess of a foot are likely.

Heavy snow is likely across the Central Rockies on Tuesday. Image provided by the College of DuPage.

 

While the snow gets the headlines, the cold air behind the front will be making headlines of its own. The first frost and freeze of the season is likely across the Dakotas Tuesday and/or Wednesday morning, with lows in the upper 20s and 30s. The cold air will continue to push southward across the Great Plains during the day on Tuesday, with numerous record lows expected Wednesday morning as far south as the Texas Panhandle.

Record lows are likely across the Plains and the Rockies Wednesday morning. Image provided by Weathermodels.com

 

While plenty of precipitation is expected across the Rockies, the lack of it is causing problems across the Northeast. Aside from a few showers with a cold front on Thursday, generally dry weather is expected across much of New England this week. This shouldn’t be a surprise, as precipitation has been generally below to well below normal across the region since the Spring. In some areas, the amount of rain has only been around 50-60% of normal. Drought conditions have developed across nearly all of New England, and for a good portion of the region, it is now considered a severe drought. What the region needs is a series of systems that can produce moderate rainfall to help alleviate the drought, but prospects for that aren’t promising at this time. In fact, rainfall looks to remain below normal for much of the remainder of September.

Severe drought conditions have developed across parts of New England. Image provided by the National Drought Mitigation Center.

 

Meanwhile, as we approach the climatological peak of hurricane season, the Atlantic is once again getting more active. Tropical Storms Paulette and Rene both developed on Monday in the central and eastern Atlantic respectively. Paulette is expected to remain a tropical storm for the next several days while remaining over open water. It is not expected to be a threat to land. Meanwhile, Tropical Storm Rene moved through the Cabo Verde Islands Monday night, producing heavy rain and gusty winds. It will likely strengthen over the next couple of days, possibly becoming a hurricane later this week. Once it pulls away from the Cabo Verde Islands it is also expected to remain over open water for much of this week, presenting no additional threat to land.

Satellite loop showing Tropical Storms Paulette and Rene in the central and eastern Atlantic. Loop provided by Tropical Tidbits. (Click for Loop)

 

Those systems aren’t the only ones in the Atlantic that are being watched. An area of low pressure a couple of hundred miles southwest of Bermuda is expected to drift westward over the next few days. Some development of the system is possible. It may bring some rainfall into parts of the Carolinas and Southeast late this week. The other area that is being watched isn’t apparent right now, as it is still over western Africa. A tropical wave is expected to emerge from the west coast of Africa late this week. Forecast models show the potential for this wave to develop rather quickly once it moves into the Atlantic. It could threaten the Cabo Verde Islands over the weekend.

Models show the potential for 2 tropical systems to develop over the next several days. Image provided by the University at Albany.

 

The peak of hurricane season is during the middle to latter half of September. Given how active this season has been so far, there will likely be more systems developing. There are only 4 names left on this list for this season – Sally, Teddy, Vicky, and Wilfred. Once the list is exhausted, the Greek alphabet is used. This has only happened once before – in 2005. During that season, there were 28 named storms of which 15 became hurricanes.

Hurricane Laura Approaches the Gulf Coast

Hurricane Laura is now a Category 3 hurricane with its sights set on the Gulf Coast.

Hurricane Laura has the appearance of a classic hurricane on satellite this morning. Loop provided by Tropical Tidbits. (Click for Loop)

As of 11am EDT, Hurricane Laura was centered about 225 miles south-southeast of Lake Charles, Louisiana, moving toward the northwest at 16 mph. Maximum sustained winds have increased to near 125 mph, making Laura a Category 3 Hurricane. A buoy in the central Gulf of Mexico reported sustained winds of 76 mph and a gust to 107mph as the center of Laura passed nearby this morning. Hurricane and Storm Surge Warnings are in effect for portions of the Texas and Louisiana coastline, with Tropical Storm Warnings, Hurricane Watches, and Storm Surge Watches for areas adjacent to the warning areas.

Numerous watches and warnings are in effect associated with Laura. Image provided by the National Hurricane Center.

The forecast for Laura is rather simple at this point. It will continue heading northwest towards a trough of low pressure moving across the nation’s mid-section. Landfall is expected tonight very close to the Texas/Louisiana border. The only question is, how strong will Laura get? Many forecast models bring Laura up to Category 4 intensity before landfall, which would mean sustained winds of 131-155 mph. However, intensity forecasts are notoriously poor. One thing that could limit intensity would be an eyewall replacement cycle. In stronger hurricanes, you’ll get a second eyewall that forms outside the center. That eyewall will eventually start to contract towards the eye, replacing the current eyewall. When this occurs, storms tend to weaken a bit. These are very hard to predict in advance.

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

Laura presents many threats to the Gulf Coast. A storm surge of up to 15-20 feet will inundate coastal areas near and just to the east of where the center makes landfall. This will result in flooding across many of the bayous of southern Louisiana. Strong winds will obviously be a major hazard as well, mainly east of the center. The strong winds will likely penetrate well inland, as the storm will be powerful, though it should start to weaken fairly rapidly once inland.

Storm surge will be a significant threat along the Gulf Coast. Image provided by the National Hurricane Center.

By far, the biggest threat, as it is with most tropical systems, is heavy rain and the freshwater flooding it will produce. Rainfall totals of 10-15 inches and locally heavier are likely across extreme southeast Texas and western Louisiana. Since Laura is moving fairly quickly and not expected to stall out, we shouldn’t see a repeat of the 30-60 inches that Harvey produced in the same area 3 years ago this week.

Laura will produce very heavy rainfall through Friday evening. Image provided by Pivotal Weather.

Farther inland, rainfall totals of 3-6 inches are expected up into Arkansas. As the storm gets caught up in the jet stream and becomes extratropical, it will bring heavy rain to parts of the Ohio Valley and Mid-Atlantic states Friday into Saturday. Once it moves off the coast, it may strengthen a little, and could enhance some of the rain expected across New England and Atlantic Canada this weekend associated with a cold front.

Once Laura moves inland, the Atlantic should remain quiet for the next week or so. Plumes of Saharan Dust continue to move off the west coast of Africa and traverse the Atlantic and Caribbean. The very dry air associated with these plumes inhibits thunderstorm development, which means they also prevent tropical systems from developing.

Plumes of Saharan Dust will make their way across the Atlantic over the next several days. Loop provided by Weathermodels.com (Click for Loop)

Laura isn’t the only active storm in the tropics right now. This morning two separate tropical depressions have developed in the Eastern Pacific, off the southwestern coast of Mexico. Both are expected to become tropical storms in the next 24-36 hours, but remain relatively weak. Tropical Depression 13-E may bring some heavy rain and gusty winds to southern portions of Baja California late this week, but Tropical Depression 14-E should not impact any land areas.

Typhoon Bavi is expected to make landfall in North Korea this evening. Image provided by the Korean Meteorological Administration.

In the Western Pacific, Typhoon Bavi has maximum sustained winds near 110 mph as it moves into the Yellow Sea. The current forecast calls for the storm to make landfall in western North Korea this evening, then rapidly weaken as it moves inland into extreme northeastern China. As with Laura, strong winds and storm surge will have significant impacts on the region, but rainfall totals of 4-8 inches and locally heavier will result in flooding in many areas.

Two Tropical Systems Threaten The Gulf

Parts of the Gulf Coast could get a 1-2 punch from a pair of tropical systems during the upcoming week.

Tropical Storms Marco (left) and Laura (right) are both heading toward the Gulf Coast. Loop provided by Tropical Tidbits. (Click for loop)

 

Tropical Storm Marco is the more immediate threat. As of 11am EDT Sunday, Marco was centered about 325 miles south-southeast of the mouth of the Mississippi River, moving toward the north-northwest at 14 mph. Maximum sustained winds were near 70 mph. Tropical Storm and Hurricane Watches and Warnings as well as Storm Surge Watches and Warnings are in effect for portions of the northern Gulf Coast.

Marco’s forecast is a bit complicated. The warm waters of the Gulf provide ample fuel for Marco to strengthen, and it could become a hurricane later today. However, as it heads northward, southwesterly shear will increase, which will help weaken the storm. Although hurricane warnings are in effect, Marco could weaken to a tropical storm before making landfall, likely along the Louisiana coast Monday afternoon or evening.

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

 

Marco will produce strong winds, mainly along the coast, and a storm surge of up to 6 feet will result in flooding along the coast and in the low-lying bayous of southern Louisiana. However, Marco’s biggest threat will be flooding from heavy rainfall. Rainfall totals of 3-6 inches and locally heavier will result in flooding in many areas. This is exacerbated in New Orleans, where much of the city itself is below sea-level and even heavy thunderstorms can produce flooding.

ECMWF model forecast for rainfall through Wednesday morning. Image provided by Weathermodels.com

 

Marco is the initial threat, but Tropical Storm Laura is a more significant threat to the Gulf Coast. As of 11am EDT Sunday, Laura was centered about 95 miles southeast of the eastern tip of Cuba, moving toward the west-northwest at 21 mph. Maximum sustained winds were near 50 mph. Tropical Storm Warnings are in effect for parts of the Dominican Republic, Haiti, Cuba and the Southeastern Bahamas, with Tropical Storm Watches in effect for the Central Bahamas and the Florida Keys.

In the near-term, Laura is expected to traverse the entire length of Cuba for the next day or so, producing heavy rain and gusty winds. Heavy rains will diminish across the Dominican Republic and Haiti today as Laura pulls away.  With the center interacting with land, little strengthening is anticipated for the next 24-36 hours, and some weakening is possible. Once we get to late Monday, things become a bit more complicated.

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

 

Laura is expected to move into the southeastern Gulf of Mexico Monday evening as a tropical storm. Once it does, it will find an environment that is favorable for strengthening. Water temperatures are well into the 80s, providing plenty of fuel for the system. (Tropical systems need water warmer than 80F/26C to survive/strengthen) A ridge of high pressure will also be building in aloft, resulting in very little wind shear. This is also an area that climatologically favors rapid intensification of tropical systems. Several models show the potential for Laura to quickly become a hurricane and possibly a major hurricane as it moves across the Gulf of Mexico on Tuesday. It should be noted that intensity forecasts for tropical systems, especially from forecast models, have been known to be rather poor.

Water temperatures in the Gulf of Mexico are quite warm at this time. Image provided by Tropical Tidbits.

 

The track forecast for Laura is also a bit uncertain. The ridge of high pressure building in will help steer Laura more towards the west-northwest. How strong that ridge actually is will help determine how far west Laura moves. While the models were nearly unanimous just 24 hours ago that Laura was heading towards the Central Gulf Coast, they have shifted westward, putting parts of Texas and western Louisiana in the crosshairs. Additional shifts are likely over the next day or two as the models adjust to what is actually going on in the atmosphere. For now, residents of the Gulf Coast from Central Texas to Alabama should keep a close eye on Laura’s progress.

Forecast tracks from the 51 members of the ECMWF Ensemble forecast. Image provided by Weathermodels.com

 

There are no other systems in the Atlantic that are being monitored right now, but we are approaching the peak of Hurricane Season, so that will likely change soon. There are two systems in the Eastern Pacific that may become tropical depressions in the next day or two, and Typhoon Bavi will be a threat to South Korea over the next 24-48 hours in the Western Pacific.

Tropical Storm Isaias Heads Toward the Carolinas

While crossing the Bahamas on Saturday, Hurricane Isaias weakened to a tropical storm, but it remains a threat to much of the East Coast.

Isaias continues to spin off the Florida coast. Loop provided by NOAA. 

 

As of 5pm Sunday, Tropical Storm Isaias was centered about 65 miles southeast of Vero Beach, Florida, moving toward the north-northwest at 9mph. Based on data from reconnaissance aircraft and Doppler Radar on the Florida coast,  maximum sustained winds have increased to near 70 mph, and should remain near that level for the next day or two, with some fluctuations in strength possible.

Tropical Storm Warnings are in effect from Sebastian Inlet, Florida to Ocracoke Inlet North Carolina. A Hurricane Watch has also been issued from South Santee River, South Carolina to Surf City, North Carolina. A Storm Surge Warning is now in effect from Edisto Beach, South Carolina to Cape Fear, North Carolina and a Storm Surge Watch is in effect north of Surf City to Duck, North Carolina, including Albemarle and Pamlico Sounds. In additional, the Tropical Storm Watch has been extended northward, now extending from Ocracoke Inlet, North Carolina to Watch Hill, Rhode Island. This includes Chespeake Bay, the Tidal Potomac River, Delaware Bay, and Long Island Sound, as well as the cities of Washington and New York.

Isaias moved across the Bahamas as a hurricane late Friday into early Saturday, before weakening to a Tropical Storm Saturday afternoon. The combination of southwesterly wind shear and some dry air due to Saharan Dust contributed to the weakening. Isaias is maintaining its strength this afternoon despite the presence of more wind shear.

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

 

Isaias should continue to head towards the north tonight and Monday, in between a large area of high pressure of the east, and an approaching trough of low pressure from the west. As the trough continues to move towards the East Coast, it will help turn Isaias more towards the north-northeast and eventually northeast. On this track, Isaias will parallel the coast of Florida and Georgia tonight and Monday, then likely make landfall in either South Carolina or North Carolina late Monday night or early Tuesday. Once inland, Isaias will continue northeastward, and although it will weaken a bit, it should maintain some strength as it moves up the coast, as it starts to transition into an extratropical storm.

Storm surge will be a threat along the Carolina coast, near and east of where the center makes landfall. A surge of up to 4 feet above normal tide levels could result in some coastal flooding. Strong winds will also be a threat, mainly east of the storm’s center. Winds have been gusting as high as 50 mph along the Florida coast this afternoon. As it moves northward, some strong winds will be likely across eastern North Carolina as the storm moves inland, and possibly across eastern New England late Tuesday into early Wednesday as the system moves across the Northeast.

Most of the strongest winds should remain offshore. Image provided by WeatherBell.

 

By far, the biggest threat with Isaias is heavy rainfall and the resulting flooding. Some bands of heavy rain have moved across parts of Florida, and that will continue through tonight. Rainfall totals of 1-3 inches are possible across parts of Florida and Georgia over the next 24-36 hours. As you head north, heavier rain is likely from the Carolinas into the Mid-Atlantic states and the Northeast, mainly along and west of the storm’s track. Rainfall totals of 3-6 inches and locally heavier are likely, which will produce flooding in many areas. The storm’s relatively quick motion will preclude even heavier totals. East of the storm’s track, rainfall will be much lighter, with many places likely seeing less than 1 inch.

Isaias will produce heavy rainfall across much of the East Coast over the next few days. Image provided by Weathermodels.com.

 

Elsewhere, we’re keeping an eye on a tropical wave located a few hundred miles east of the Leeward Islands. Conditions could become favorable for it to develop into a tropical depression in a few days. Model forecasts show it heading northwestward, staying north of the Caribbean over the next few days. By mid-week, most forecasts show it stalling out about midway between Bermuda and the Bahamas. It does not look like a threat to any land areas at this time.

Isaias Heads Toward the Bahamas, Is the East Coast Next?

Tropical Storm Isaias has strengthened into a hurricane this evening as it starts to pull away from the Dominican Republic and head towards the Bahamas. Meanwhile, the threat to the East Coast is starting to increase.

As of midnight Friday morning, Isaias was centered about 80 miles southeast of Great Inagua Island in the southeastern Bahamas, and was moving toward the northwest at 18 mph. Maximum sustained winds have increased to 80 mph based on recent data from reconnaissance aircraft. A Hurricane Warning is in effect for the northwestern, central, and southeastern Bahamas.Tropical Storm Warnings remain in effect for the entire Dominican Republic, the north coast of Haiti and the Turks and Caicos Islands. A Tropical Storm Watch is in effect for the east coast of Florida from Ocean Reef to Sebastian Inlet.

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

 

The short-term forecast for Isaias is rather simple. It will continue to move toward the northwest across the Bahamas while gradually slowing down. Waters remain very warm in this area (29-31C), and wind shear shouldn’t be that strong, which will allow Isaias to strengthen a bit more over the next day or two.

Once Isaias gets into the northwestern Bahamas, things get a bit trickier. A large high pressure area in the western Atlantic, and a trough of low pressure moving into the eastern United States will help to steer Isaias more towards the north-northwest, and then north, and eventually northeast. Exactly when those turns occur is critical to the forecast.

Model forecasts are fairly unanimous about a threat to parts of the East Coast. Image provided by WeatherBell.

 

The current forecast calls for Isaias to make the northward turn east of Florida, sparing the Sunshine State from the worst of the storm. It may be close enough to bring some gusty winds and heavy rain to east-coastal Florida over the weekend, which is why the Tropical Storm Watch has been issued. That watch will likely be extended farther north on Friday. After that, it will head towards the Carolina coastline late Sunday into Monday. This is where the uncertainty is magnified.

GFS forecast for the upper-air pattern over the US for the next 5 days. Loop provided by Tropical Tidbits. (Click for loop)

 

If the Western Atlantic high is stronger than currently expected, or if the trough moving into the East is sharper than the models are currently showing, then Isaias will continue northward, likely moving across eastern North Carolina. A weaker high or flatter trough, would allow for a more northeastward movement, which could allow Isaias to only graze the Outer Banks or possibly even miss them completely.

Once the storm is beyond the Carolinas, there is more uncertainty with its track. Again, a more northeastward motion will bring the storm out to sea with little additional impact. A motion that is more toward the north-northeast or even north, would increase the threat to parts of the Northeast, including New England for late Monday or Tuesday.  As this point, coastal residents from Florida to New England should all keep tabs on the storm’s progress, as it could impact a large stretch of coastline this weekend and early next week.

Isaias has produced tropical storm force winds across much of the northern and northeastern Caribbean. Image provided by the National Hurricane Center.

 

Isaias was well-advertised by the models for almost a week before it finally developed over the eastern Caribbean on Wednesday. It has produced wind gusts of up to 60 mph and heavy rain that produce flooding across parts of the Virgin Islands, Puerto Rico, and the Dominican Republic. Wind gusts as high as 54 mph have also been reported in the Turks and Caicos Islands this evening.

The Tropics Are Active Again

The tropics had been relatively quiet in the past couple of weeks, but now there are suddenly 3 storms that are all threats to land by the end of the weekend.

Tropical Depression 8 is trying to get organized in the Gulf of Mexico while Tropical Storm Gonzalo heads toward the Windward Islands. Loop provided by NOAA. (Click for Loop)

The most immediate threat is Tropical Depression 8. As of 11am EDT, the system was centered about 380 miles east-southeast of Port O’Connor, Texas, moving toward the west-northwest at 9 mph. Maximum sustained winds were near 35 mph. The system should continue on a general westward track for the next day or two, with some strengthening possible. If it does strengthen, it would be named Tropical Storm Hanna. Since this is possible, a Tropical Storm Watch is in effect for most of the Texas coast from Port Mansfield to High Island.

Forecast track for Tropical Depression 8. Image provided by the National Hurricane Center.

While gusty winds and some rough surf are likely along the Texas coast, the biggest threat from this system will be heavy rainfall. Slow-moving tropical systems have produced significant rainfall in Texas many times before, and while we’re not expecting 50+ inches like Hurricane Harvey produced a few years ago, widespread totals of 3-6 inches with isolated amounts of up to 10 inches are possible through this weekend and early next week. That would likely produce flooding in many areas.

TD 8 will produce heavy rain across much of southern Texas and parts of the Gulf Coast. Image provided by WeatherBell.

While TD 8 is the immediate threat to the US, out in the Atlantic, Tropical Storm Gonzalo presents a threat to the Southern Windward Islands. As of 11am EDT, Gonzalo was centered about 885 miles east of the southern Windward Islands, moving toward the west at 14 mph. Maximum sustained winds were near 65 mph. A Hurricane Watch is in effect for Barbados as well as St. Vincent and the Grenadines.

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

Gonzalo’s future is very uncertain at this point. The official forecast from the National Hurricane Center calls for Gonzalo to become a hurricane later today, then start to weaken after moving across the Windward Islands this weekend and into the eastern Caribbean. However, Gonzalo looks less organized on satellite photos today, and is fighting off some dry air aloft. There is a decent chance that the system could weaken or even open up into a wave before reaching the Windward Islands. How it develops over the next 12-24 hours will give us a much better idea of what the future holds for it.

In the Eastern Pacific Ocean, Hurricane Douglas continues to strengthen this morning, and could become a threat to Hawaii this weekend.

Hurricane Douglas continues to strengthen in the Eastern Pacific Ocean. Loop provided by NOAA. (Click for Loop)

As of 11am EDT, Douglas was centered about 1335 miles east-southeast of Hilo, Hawaii, moving toward the west-northwest at 20 mph. Maximum sustained winds have increased to 120 mph, making Douglas a Category 3 storm on the Saffir-Simpson scale. Some additional strengthening is possible today before a weakening trend begins on Friday as Douglas moves over cooler waters.

Forecast track for Hurricane Douglas. Image provided by the National Hurricane Center.

Douglas is expected to only gradually weaken while heading towards the west-northwest over the next several days. On this track, Douglas is expected to pass close to or over parts of the Hawaiian Islands this weekend. Obviously which islands would be impacted and what the threats would be will depend on the exact track Douglas takes, as well as how quickly it weakens. At this point, gusty winds, heavy rainfall, and rough surf appear mostly likely for the Big Island, but the entire island chain could be impacted.

While Hawaii has been impacted by many weakening storms passing by the islands, a direct hit is actually fairly rare. Since 1871, only 3 hurricanes and 4 tropical storms have actually made landfall on the islands. The last system to make landfall in Hawaii was Tropical Storm Olivia in 2018. The last hurricane to make landfall in Hawaii was Hurricane Iniki in 1992.

Very few tropical systems actually make landfall in Hawaii. Image provided by NOAA.

Beyond these systems, there’s nothing on the immediate horizon. Some of the longer-range ensemble models are showing the potential for a wave to move off the the African coast and develop while crossing the Atlantic next week. This is still several days away, and while the likelihood of it happening is fairly low, we are getting into the time of year when some of these waves do start rolling off of Africa and maintain themselves while crossing the Atlantic.

Tropical Storm Fay Develops off the East Coast

Tropical Storm Fay developed off the North Carolina coastline Thursday evening, the sixth named storm of the season.

Satellite loop of Tropical Storm Fay developing off the North Carolina coastline. Loop provided by NOAA.

 

A disturbance that moved from the Gulf of Mexico and into the Southeast last week moved off the South Carolina coast on Wednesday. After sitting over the warm waters of the Gulf Stream, thunderstorm activity began to increase, and a new center of circulation developed Thursday afternoon. Air Force Reserve Hurricane Hunters investigating the system determined that it had a closed circulation, and the system was designated as Tropical Storm Fay.

Fay is the 6th named storm of the season (Whether all 6 deserved to be named is debatable), and is the earliest we’ve ever had an “F” storm in the Atlantic. The previous record was held by Tropical Storm Franklin during the 2005 season, which developed on July 22.

While there are still a few details that need to be determined, Fay’s future is fairly clear. With a ridge of high pressure in the western Atlantic, and a trough of low pressure moving into the Great Lakes, Fay should head northward for the next 24-48 hours, paralleling the Mid-Atlantic coastline. While the official forecast from the Hurricane Center keeps the center just offshore until it makes landfall near New York City Friday night, a slight jog to the west would bring the center into the New Jersey coastline. A Tropical Storm Warning has been issued from Cape May, New Jersey to Watch Hill, Rhode Island, including Long Island Sound. This includes all of Long Island and New York City.

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

 

Fay currently has maximum sustained winds near 45 mph, and some modest strengthening is possible overnight and early Friday. The storm is moving northward at 8 mph, and should pick up a little speed on Friday. This track will keep most of the strongest winds offshore, until the center reaches Long Island Friday night.

Fay will bring heavy rain to portions of the Mid-Atlantic states. Image provided by Weathermodels.com

 

Fay’s biggest threat will be heavy rainfall that could lead to flash flooding, especially from the Mid-Atlantic states into eastern New York and western New England. Much of this region has been dry for a few months, and drought conditions are beginning to develop. Some of this rainfall will help alleviate that, but too much rainfall too quickly will just run off and not help much at all. By the time Fay pulls away early Saturday, rainfall totals of 2-5 inches are expected from the Delmarva Peninsula into western New England and eastern New York, mainly along and just west of the expected track of Fay. Some isolated totals in excess of 6 inches are possible. Amounts will taper off the farther east or west you head away from this area.

Drought conditions are staritng to develop across the Northeast. Image proviuded by the National Drought Mitigation Center.

 

This track is very similar to the track that Hurricane Irene took in 2011. Irene had weakened to a tropical storm before crossing New York City and heading up the Hudson Valley, producing significant flooding across western New England. Irene is the last tropical system to make landfall in New York or New England. On average, a tropical storm makes landfall in this area once every 4.7 years, and the 9 years without a storm is just shy of the record of 11 years the region went between 1923 and 1934. The last hurricane to make landfall in the region was Bob in 1991. The 29 year deficit is triple the average of 9.4 years between storms, and is the 2nd longest drought on record, trailing the 38-year drought between 1896 and 1934.

Actual track of Hurricane Irene in 2001. Image provided by Florida Institute of Technology.

 

Once Fay dissipates, there don’t appear to be any other areas that may develop in the next week or two. It’s still early in the season, and easterly waves will begin rolling off of western Africa soon, with the climatological peak of hurricane season still more than a month away.

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