Monday, August 29, 2016

Yet another tropical system may emerge as a post-Labor Day threat to Caribbean, US

By , Senior Meteorologist
August 29,2016; 11:05AM,EDT
Another strong tropical disturbance, moving off the coast of Africa, bears watching for strengthening. While still several days away, the system may impact the Caribbean and United States during September.
Even as the Atlantic is teeming with tropical systems this week, another may join in the frenzy before the week comes to a close.
In addition to Tropical Depression Eight, Tropical Depression Nine and Hurricane Gaston, the train of disturbances moving off of Africa has the potential to produce another tropical system worth tracking for the long-term.
This is a closeup live loop of the tropical disturbance. (NOAA/Satellite)
The disturbance is likely to take a path much farther west than Gaston, which turned northward over the middle of the Atlantic Ocean.
During Tuesday the disturbance will be near Cabo Verde, formerly known as the Cape Verde Islands.
"This disturbance will move westward over the Atlantic in an environment generally favorable for tropical development during the balance of this week," according to AccuWeather Hurricane Expert Dan Kottlowski.

Fast motion between 15 and 20 mph (24 and 32 km/h), along with pockets of dry air and disruptive winds along the way, may hinder rapid development of the system initially.
The system could impact the Leeward Islands around Sunday, Sept. 3, or Monday, Sept. 4, with rough seas, drenching showers and locally gusty thunderstorms.
Steering winds could then guide the system on a curved path during the balance of next week.
As a result the new system may not travel as far west as Tropical Depression Nine did.
It is possible the system could roll near Puerto Rico and then Bahamas before turning northward near the Atlantic coast of the United States around the second weekend of September.
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Provided the system avoids the larger islands of the Caribbean, disruptive winds and dry air, there is the potential for development to a tropical depression, tropical storm and a hurricane in the days ahead.
There is the potential for additional systems to form in the coming weeks with the peak of hurricane season on Sept. 10 and hurricane season continuing through October and into November.

Warm fall may jeopardize foliage displays in northeastern US

By Jillian MacMath, Staff Writer
August 29,2016; 7:33AM,EDT
Though the summer season is winding down, forecasters are predicting a warm start to fall across the Northeast - a weather pattern that could spell bad news for fall foliage lovers.
AccuWeather meteorologists are calling for a warmer-than-normal fall for much of the nation, including the northeastern U.S., a region renowned for its expansive forests and vibrant seasonal foliage displays.
Dry conditions paired with warm weather, which is expected to stretch into the first half of autumn, may make the colors less dramatic than usual.
"I think fall foliage this coming season will be actually hurting just a bit here in the Northeast," AccuWeather Expert Long-Range Forecaster Paul Pastelok said.
Trees require certain cues in early autumn to signal foliar color change and leaf fall, Michael Day, associate research professor for Physiological Ecology at the University of Maine, told
The Northeast's lack of rainfall and absence of chilly air may stifle these processes.
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"The trees will probably be too dry and the vibrant colors won't come out," Pastelok said. "If they do come out, they'll be short-lived and probably knocked down too fast to be enjoyed..."
September and October are critical months for the weather in fall foliage regions.
Snow on ski trails at the Sugarbush ski area are seen on mountaintops with fall colors on the hillside on Monday, Oct. 8, 2012 in East Montpelier, Vt. (AP Photo/Toby Talbot)
During this time, trees rely on a cold snap, particularly during the nighttime hours, which lasts for several days, Day said.
According to AccuWeather's 2016 U.S. fall forecast, typical cool shots will invade the region at times in October and November, but a persistent chill won't arrive until after the fall season.
Though leaf peepers may have to look elsewhere for dramatic displays of oranges and reds, Pastelok says the warmth may have more advantages than disadvantages.
Conditions will be ideal for those planning to attend fall festivals and outdoor sporting events or for anyone tackling outdoor projects, he said.

Top 5 US cities most vulnerable to hurricanes

By Kevin France, Staff Writer
August 29,2016; 7:30AM,EDT
In any given year, there are some U.S. cities that are at higher risk than others to experience the impacts of a hurricane.
Based upon data from NOAA's Hurricane Research Division, here are the top five most vulnerable U.S. cities to hurricanes.
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"The probabilities are based upon 126 years of hurricane data and storm paths dating back to the 1800s," AccuWeather Hurricane Expert Dan Kottlowski said. "These numbers are not based upon property damage but instead focus on the chances that a hurricane will strike a region based upon factors such as geography and location."
Miami, Florida
Miami & Fisher Island from 500ft. (Flickr Photo/Mohd Althani)
Miami takes the number one spot on this list with a 16 percent chance of experiencing the impacts of a hurricane in any given year. Based on historical data, on average a hurricane will pass within 50 miles of the Miami metropolitan area every six to eight years. With the Atlantic Ocean to the east and a maximum elevation of 42 feet above sea level Miami's geography makes it highly vulnerable to hurricanes.
In addition to this, a majority of the population resides within 20 miles of the coastline increasing the risk of high property damage.
"Miami has a large population density, and as a result, the effects of a major hurricane would be catastrophic to the city," AccuWeather Meteorologist David Samuhel said. "Also, because of its southern location, Miami is probably the largest city on this list to see a Category 4 or 5 hurricane in the future."
Although a major hurricane is long overdue in Miami, the city has dealt with its share of intense hurricanes in the past. The last major hurricane to affect the city was Hurricane Andrew in 1992, which packed winds of 165 mph and currently holds the record as the third strongest U.S. landfalling hurricane. Andrew's total damage cost was $26.5 billion as communities in the surrounding areas were severely affected due to its intense winds and high storm surge.
Key West, Florida
Key West. (Flickr Photo/Harold Navarro)
Key West, like Miami, has a 16 percent chance of being impacted by a hurricane during any Atlantic hurricane season. Known as the Southernmost City in the Continental United States, Key West is directly impacted by a hurricane every 5.96 years, according to Hurricane City.
The Florida Keys are an archipelago of about 1,700 islands spanning 113 miles with Key West located at the southern tip. With the Atlantic Ocean to the south and east and the Gulf of Mexico to the north and west, the coastal town is exposed to all sides to passing hurricanes.
Key West with maximum elevation of 18 feet above sea level makes it susceptible to heavy flooding and storm surge during a hurricane event. Hurricane Wilma in 2004, regarded as the worst storm to hit the area, passed just west of Key West and produced a storm surge of 8 feet leaving 60-70 percent of the island under water.
"Key West has faced several situations in the past where it has been brushed or directly affected by some of the strongest hurricanes to hit the United States. This includes the 1935 Labor Day Hurricane which was remembered as one of the most intense U.S. hurricanes based on pressure and maximum wind speeds," Samuhel said. "Because Key West is so far from the mainland, evacuating people can be a difficult challenge during a hurricane event."
Cape Hatteras, North Carolina
Cape Hatteras (Flickr Photo/John Blue)
Located on the Outer Banks of North Carolina, Cape Hatteras has a 15 percent chance of feeling the impacts of a hurricane in any given year. Cape Hatteras is positioned 280 miles farther east than Palm Beach, Florida, (easternmost location of the Florida coast). As a result, Cape Hatteras has been exposed in the past to hurricanes that move up the Eastern Seaboard.
"Cape Hatteras is very close to the Gulf Stream, which enables hurricanes to strengthen due to warmer ocean temperatures during the summer," Samuhel explained. "Typically, when tropical systems get caught in the jet stream off the East Coast of the U.S., they tend to curve out to sea, but because of the location of Hatteras, hurricanes tend to clip that region before affecting anywhere else on the East Coast."
When Hurricane Isabel struck the region in 2003, the Army Corp of Engineers was forced to fill up an inlet that was created when the storm split Hatteras Island between Frisco and Hatteras, North Carolina.
Tampa, Florida
Tampa Skyline (Flickr Photo/Sonny Side Up!)
The western coast of Florida has endured its share of hurricanes, and the city of Tampa is no exception. The Tampa-St. Petersburg area has an 11 percent chance of feeling the impacts of a hurricane in any given year. Tampa, situated on a peninsula lying along Tampa Bay and the Gulf of Mexico, is exposed to hurricanes entering the Gulf and systems forming in the Atlantic. Many of the 347,645 people living in the area have homes along the coast, making residents susceptible to storm surge.
"Like Miami, Tampa is a large metropolitan area and the effects of a hurricane would be widespread throughout the city," Samuhel explained. "Because it is located by the shallow Tampa Bay, water piles up into the city, causing very significant storm surge along the coastline."
The city hasn't suffered a direct hit by a strong hurricane since the 1921 Tampa Bay Hurricane, the first major hurricane to hit the city, but 68 tropical storms and hurricanes have passed within 60 miles of the city according to Hurricane City. Most recently in 2004, Hurricane Charley caused $16 billion in damages when the Category 4 storm made landfall just south of Tampa.
New Orleans, Louisiana
Streetcar in New Orleans (Flickr Photo/faungg's photos)
Hurricane Katrina in 2005 shined the light on how devastating a tropical system can be for the city of New Orleans. Like Tampa, The Big Easy has an 11 percent chance of experiencing the impact of a hurricane in an average year. According to NOAA, a hurricane makes landfall within 50 miles of New Orleans about once every seven to 11 years.
The city has since made drastic improvements to its levee system since Katrina left most of the city under several feet of water. Nevertheless, with more than 50 percent of the city living below sea level and the rapid sinking of marshy coastal land in southeastern Louisiana, New Orleans still remains highly vulnerable to storm surge during a major hurricane.
"The Mississippi River is almost 30 feet above the city level just to put in perspective of how low New Orleans is in terms of elevation," Samuhel said. "The land around New Orleans is sinking, which puts the city in more danger if another major hurricane strike."

World Weather Hot Spot for August 29-30,2016 from

Basco,Philippines: Very heavy rain;received a whopping 5.2 inches of rain in 24-hours on Sunday (August 28,2016)

WeatherWhys for August 29,2016 from

Hurricane Katrina made landfall along the southeast coast of Louisiana as a Category 3 storm on this date in 2005. The hurricane caused over a $100 billion in damage and was responsible for the deaths of over 1,800 people.

Atlantic Has Three Tropical Cyclones at Once for First Time in Nearly Three Years

Chris Dolce
Published: August 29,2016

For the first time in nearly three years, the Atlantic basin has three tropical cyclones active at the same time.
As of Monday morning, the three tropical cyclones are Tropical Depression Nine in the southeast Gulf of Mexico, Tropical Depression Eight to the east of North Carolina, and Hurricane Gaston in the Atlantic Ocean.
(MORE: T.D. 9 | T.D. 8 | Gaston)
Circled on the satellite image are the three active Atlantic tropical cyclones on Sunday. Tropical Depression Nine (left), Tropical Depression Eight (center) and Hurricane Gaston (right).
The last time the Atlantic had three tropical cyclones active at once was Sept. 13, 2013, according to Dr. Phil Klotzbach, a tropical scientist at Colorado State University. On that day, Tropical Storm Ingrid was soaking eastern Mexico while Gabrielle and Humberto were in the Atlantic.
It's not uncommon to have multiple tropical cyclones active in the Atlantic simultaneously during the busiest part of the season, typically August into October. Records show that every year from 1998-2013 had three active tropical cyclones at once in the Atlantic during some point in the season.
In fact, twice in history there were four hurricanes in the Atlantic at the same time. That occurred on Aug. 22, 1893 and Sept. 25, 1998.
(MORE: Four Atlantic Hurricanes at Once)
Dry air and wind shear are partially the reasons that the 2014 and 2015 seasons did not have three tropical cyclones at once.
Only eight Atlantic tropical cyclones formed in 2014 due to those factors. The 2015 season had more tropical cyclones with 11 total, but many were short-lived, and therefore made it more difficult from them to overlap with each other.

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3 Things To Know About Tropical Depression Nine

Chris Dolce, Jonathan Belles and Brian Donegan
Published: August 29,2016

Tropical Depression Nine is in the Gulf of Mexico and is expected to head towards Florida as a tropical storm later this week.
Below are three things to know about this system right now.
(FORECAST: Tropical Depression Nine) 

1.) This System Had Impacts Before it Became a Tropical Depression

This system has dumped locally heavy from the Leeward Islands to Hispaniola, the Bahamas and Cuba since last week.
In the Dominican Republic, the heavy rain displaced more than 1,700 people late last week, according to the Dominican Today.
Parts of eastern Cuba saw 3-5 inches of rain from the system on Saturday.

2.) Rain Will Likely Be the Greatest Impact in Florida

A moist southerly wind flow to the east of Tropical Depression Nine will keep Florida wet the next several days.
By late this week, the actual center of the system is forecast to move northeastwards towards the Florida Gulf Coast, resulting in more rainfall.
Some flooding is expected across parts of the state throughout the week ahead since the rainfall will be heavy at times.

Forecast Rainfall
Any other impacts, such as wind and water rise along the coast, will be dependent on the intensity of the system. At the moment, however, heavy rain seems to be the biggest threat.
For more details, see our full forecast article at the link below.
(FORECAST: Tropical Depression Nine) 

3.) Why Did This System Take So Long to Become a Tropical Cyclone?

Since last week, the former Invest 99-L had been battling the two nemeses of tropical cyclones, dry air and wind shear.
Wind shear and dry air can slow or prevent the development of tropical systems.
Most recently, wind shear has been the biggest inhibitor to the development of this system.
Northerly wind shear affecting 99-L on Sunday morning is shown in orange and red between South Florida and Cuba.
Despite battling wind shear for days, a Hurricane Hunters reconnaissance mission finally found a sufficiently organized low-pressure center by Sunday evening, with collocated shower and thunderstorm activity, to prompt the National Hurricane Center to classify the previous Invest 99-L as Tropical Depression Nine.

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Gaston May Impact the Azores By This Weekend After Becoming First Major Hurricane of the Season

August 29,2016
Hurricane Gaston is well away from land in the central Atlantic Ocean, but could impact the Azores by this weekend.
On Sunday, Gaston became the first major hurricane (Category 3 or higher on the Saffir-Simpson Scale) of the 2016 Atlantic hurricane season. As of late Monday morning, Gaston was no longer a major hurricane, but still very powerful.
Here's the latest on Gaston:
  • Gaston was more than 500 miles east of Bermuda, as of Monday.
  • The system is expected to weaken some through the next few days, but remain a hurricane through at least late week.
  • While over 1,000 miles off the East Coast, Gaston is also likely to generate swells that will reach the East Coast Monday and Tuesday. Dangerous rip currents are possible.
  • Gaston may get close to the Azores in the northeast Atlantic by Friday night or Saturday, but is expected to be a tropical storm by then. Check back for updates on possible impacts.

Current Storm Status

Projected Path

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Hurricane Madeline Rapidly Intensifies; Could Threaten Hawaii Wednesday

Jonathan Belles
Published: August 29,2016

Hurricane Madeline rapidly intensified from Sunday into Monday morning, becoming the second named storm to become a hurricane in the central Pacific Ocean. Madeline may take a close swipe at parts of the Hawaiian Islands in the days ahead.
Madeline's estimated peak surface winds increased from a 50 mph tropical storm Sunday morning, to a 100 mph Category 2 hurricane Monday morning.
There will likely be an increase in high surf across Hawaii, but rain and wind may also be impacts depending on the exact track and intensity of the storm.
(MORE: Lester Could Also Threaten Hawaii)
Here's the latest from the Central Pacific Hurricane Center:
  • Hurricane Madeline was located just under 700 miles east of Hilo, Hawaii.
  • The system will move near or south of Hawaii on Wednesday (local time) and could be a minimal hurricane or tropical storm at that time.
  • It's too soon to tell what kind of rain and wind impacts to expect in Hawaii, as that will depend on the exact track and intensity of Madeline. The Big Island seems most likely to see rain and wind impacts, if any.
  • High surf is likely no matter what.
  • Hawaii residents and visitors should be aware of the latest updates and make necessary preparations if Madeline targets the islands.

Current Storm Status

Projected Path
Hawaii County Civil Defense is already keeping an eye on both Madeline and Lester.
The Big Island's interim civil defense administrator Ed Teixeira told KHON-TV the county cleared culverts and trimmed trees ahead of Tropical Storm Darby in July, helping to limit the damage from that storm.
The county has a list of preparedness tips on its website.
In the end, Madeline may take a similar track as Iselle did in August 2014, only the second tropical storm of record to landfall on the Big Island.
As the Central Pacific Hurricane Center rightly points out, track uncertainties just three days out with central Pacific tropical cyclone are about 130 miles.
Given Madeline's hurricane-force winds only extended up to 25 miles from the center Monday morning, these uncertainties are important for the ultimate impacts in Hawaii.
Check back with us at for updates on this system.

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Tropical Storm Watch Issued: Tropical Depression Eight May Bring Rain, Wind to North Carolina's Outer Banks

August 29,2016
Tropical Depression Eight may be a nuisance to your last-minute summer getaway to the Outer Banks of North Carolina the next few days.
This depression formed Sunday in the western Atlantic Ocean between North Carolina and Bermuda after a flare-up of thunderstorms near its well-defined low-level circulation.
A tropical storm watch has been issued for portions of the Outer Banks of North Carolina. This means tropical storm-force winds are possible within the watch area in the next 48 hours or less.

Current Tropical Storm Watches
The depression was centered about 180 miles southeast of Cape Hatteras, North Carolina, as of late Monday morning.
(MORE: T.D. Nine a Gulf Coast Threat)

Current Storm Information
T.D. Eight is still being affected by wind shear, and a relative lack of persistent, deep convection has not allowed the system to strengthen, as yet.
As the forecast path from the National Hurricane Center shows, this system will track to near the Outer Banks of North Carolina by Tuesday. Thereafter, a cold front will move across the Northeast and will likely whisk it away from the rest of the East Coast.
This system is not expected to become very strong as far as winds go, due to continued wind shear the next several days.

Projected Path
There will be three main impacts from this system, mainly from Tuesday into early Wednesday:
  • Tropical moisture will fuel showers and thunderstorms with locally heavy rain in far eastern North Carolina. One to three inches of rainfall in eastern North Carolina is likely with localized amounts to five inches. 
  • The system will also generate high surf and dangerous rip currents along the coastal Carolinas. However, swells from distant Hurricane Gaston are also arriving on the East Coast early this week.
  • Gusty winds may impact the Outer Banks, as well, but widespread, damaging winds are not expected.
Check back with us at for updates on this system.

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Tropical Depression Nine Struggles in Gulf of Mexico; Will Soak the Northeast Gulf Coast This Week

August 29,2016
Tropical Depression Nine may struggle a bit in the southern Gulf of Mexico before finally making a Gulf Coast landfall later this week with soaking rain and gusty winds.
This latest system was designated a tropical depression Sunday after a Hurricane Hunter reconnaissance mission finally found a sufficiently organized low-pressure center with collocated shower and thunderstorm activity.
(MORE: Hurricane Central)

Current Status

Tropical Depression Nine was centered about 170 miles west-southwest of Key West, Florida, as of late Monday morning.

Current Storm Information
Infrared satellite imagery shows a fair amount of convection over western Cuba and points south.

Infrared Satellite Image
However, this convection isn't really near the center of Tropical Depression Nine, as indicated by a Hurricane Hunter reconnaissance mission Monday morning.
This is due to northerly wind shear, blowing the convection away from the center of circulation.

Current Satellite, Wind Shear
For a tropical cyclone to intensify, wind shear needs to relax in order to allow convection to cluster near the center of circulation.
It remains to be seen how much wind shear will relax in the eastern Gulf of Mexico this week, which will have a big bearing on how strong this tropical cyclone can ultimately become.

Forecast Track/Intensity

As the National Hurricane Center's (NHC) forecast path shows, this tropical cyclone is forecast to eventually turn northeast on a path toward the Florida Gulf Coast Thursday.

Projected Path
At this time, the NHC expects this system to be a tropical storm as it approaches the Florida Gulf coast later this week. However, the intensity forecast for this system is more uncertain than usual, for the reason we mentioned above.
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After its Gulf landfall, some uncertainty remains on whether this tropical cyclone will track close enough to the coast of Georgia and the Carolinas Friday into early Saturday to bring some wind and rain, there.

One Certain Impact: Florida, Cuba Heavy Rain

The threat of heavy rainfall is not a function of tropical cyclone intensity, but rather the system's slow movement and availability of deep, tropical moisture, as we saw with an unnamed system earlier this month triggering Louisiana's epic flooding.

Radar, Watches, and Warnings
Fortunately, this system will accelerate to the northeast from Wednesday on. That faster forward motion will mitigate the heavy rain threat somewhat.
However, this system will have a deep fetch of tropical moisture along its eastern and southern flank.
So, for now, the heaviest total rainfall from this tropical system through Friday appears to line up over western Cuba, South and central Florida, including the Florida Keys, where many locations look primed to pick up at least 3 inches of total rainfall.
(FORECAST: Miami | Key West | Tampa)

Rainfall Outlook Through Friday
Of course, where bands of heavy rain stall, over 3 inches of rain could fall in an hour or so, leading to serious flash flooding, particularly in urban areas.
(MORE: Rainfall Flood Concern for Saturated Gulf Coast)
A rather expansive swath of the Gulf Coast region has been soaked in August, including the Florida panhandle
August 2016 rainfall, through August 23.
Assuming this system does strengthen, high surf would begin to build along the Gulf Coast of Florida by Wednesday, peaking Thursday, with some coastal flooding likely, as well.
The magnitude of wind and/or storm surge impacts from this system will ultimately depend on the exact intensity and track of the system later this week.
For now, if you have interests anywhere in Florida and along the Southeast coast, check back with us at for any important forecast changes in the days ahead.
(MORE: Most Intense U.S. Landfalls Have Happened in a 17-Day Period)
Now is a good time to make sure you have a plan before a hurricane hits.

Storm History

Before this system formed into a tropical cyclone, it soaked parts of the Caribbean, Bahamas and Cuba.
Late last week, more than 1,700 people were displaced from their homes in the Dominican Republic due to heavy rainfall.

Hurricane Lester a Labor Day Weekend Hawaii Threat

August 29,2016
Hurricane Lester, the 12th named storm and sixth hurricane of the eastern Pacific hurricane season, is pushing west across the open Pacific Ocean, and may have its sights set on Hawaii for the Labor Day holiday weekend.
(MORE: Madeline the First Hawaii Threat This Week)
Lester became third major (Category 3 or stronger) hurricane of the eastern Pacific hurricane season early Monday morning, and is now pushing Category 4 intensity.
Here's the latest from the National Hurricane Center:
  • Hurricane Lester was located about 1,300 miles west-southwest of the southern tip of Baja California.
  • Lester is moving west, and should continue doing so for the next several days before curling a bit more west-northwest this weekend.
  • This may bring Lester near the Hawaiian Islands by Labor Day weekend.
  • Little additional strengthening is expected before a slow weakening kicks in starting Tuesday.
  • That said, Lester could still be at least a minimal hurricane near the Hawaiian Islands Saturday into early Sunday.
  • It remains too far out in time to nail down specific impacts (rain, wind, etc.).
  • Changes in the forecast track and intensity could have important rammifications on impacts.
  • Those with interests in the Hawaiian Islands, particularly the eastern Hawaiian Islands should monitor the progress of both Lester and Madeline.

Current Storm Status

Projected Path
Check back with us at for updates on this system.

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TD 9 Organizing in the Gulf of Mexico; TD 8 Headed Towards North Carolina

By: Jeff Masters and Bob Henson , 3:39PM,GMT on August 29,2016

Tropical Depression Nine has not strengthened into a tropical storm yet, confirmed a NOAA hurricane hunter aircraft early on Monday morning, as the storm headed to the west at 7 mph on a track just north of western Cuba. The storm’s top winds remained near 35 mph, with a central pressure holding steady at 1007 mb. The strongest winds observed at a surface station on Monday morning were at Pulaski Shoals Lighthouse, located about 70 miles west of Key West, Florida, which recorded sustained winds of 31 mph, gusting to 35 mph, at 10 am EDT.

Figure 1. Latest satellite image of Tropical Depression Nine.

Satellite images on Monday morning showed a slow increase in the intensity and areal coverage of TD 9’s heavy thunderstorms. Long-range Key West radar showed heavy rain over western Cuba, where up to 12” of rainfall was expected, and a few scattered rain showers over the Florida Keys, but little in the way of low-level spiral bands. The main factor keeping TD 9 from developing was wind shear that was a moderately high 15 - 25 knots. TD 9 was also struggling with dry air, as seen on water vapor satellite imagery. Proximity to western Cuba was also interfering with development, as the storm’s counterclockwise flow of air pulled air across the mountains of Cuba into the storm. As this air descends to the ocean after crossing Cuba, warming and drying of the air occurs, robbing TD 9 of an important moisture source. Sea surface temperatures (SSTs) near TD 9’s center remained favorable for development, though, near 30 - 30.5°C (86 - 87°F).

Figure 2. Projected 5-day rainfall from 12Z (8:00 am EDT) Monday, August 29, through 12Z Saturday, September 3, 2016. Rainfall amounts of 3 - 7” are expected over most of Florida. Image credit: NOAA/NWS Weather Prediction Center.

Track forecast for TD 9: a Florida Gulf Coast landfall
For several consecutive runs, there has been model consensus among the GFS, European, HWRF and UKMET models that TD 9 will move on a west-northwest track through Tuesday morning, slow down and turn north in the central Gulf of Mexico on Tuesday afternoon, then get caught in the steering flow of a trough of low pressure passing to the north on Wednesday. These steering currents should bring TD 9 to a landfall on the Florida coast north of Tampa on Wednesday or Thursday. There is significant spread in the timing of TD 9’s landfall in Florida, with the HWRF model predicting a Wednesday afternoon landfall as a Category 1 hurricane, and the GFS and European model predicting a Thursday morning or afternoon landfall as a 40 - 45 mph tropical storm. In their 11 am EDT Monday Wind Probability Forecast, NHC’s highest odds for getting tropical storm force winds of 34+ mph from TD 9 along the Gulf Coast of Florida were 43%, 39%, and 34%, respectively, for Cedar Key, Tampa, and Apalachicola, Florida. Tropical storm-force winds may also occur on the east coast of Florida near where the storm exits the coast after crossing the state: NHC gave odds of tropical storm-force winds in excess of 30% to Orlando, The Villages, Daytona Beach, Gainesville and Jacksonville in Florida, and to King Bay in Georgia.

Intensity forecast for TD 9: more uncertain than usual
Once TD 9 pulls away from Cuba, a round of steady intensification is likely, with the system reaching tropical storm strength by Monday night. Satellite imagery late Monday morning showed that this process was already underway, with a notable increase in the storm’s organization. The SHIPS model on Monday morning predicted moderately favorable conditions for intensification, with wind shear falling to a moderate 10 - 15 knots Monday afternoon through Wednesday. SSTs will be a very warm 30 - 30.5°C (86 - 87°F), and mid-level relative humidity was predicted to be a reasonably moist 65 - 70%. However, there is a significant amount of dry air at middle and upper levels of the atmosphere that may interfere with development, and the usually reliable European and GFS models showed little development of TD 9 in their 12Z Sunday and 0Z Monday (8 pm EDT Sunday) runs because of this dry air, NHC forecaster Stacy Stewart argued in his forecast discussion on Sunday night. Our best dynamical intensity model, the HWRF model, had TD 9 intensifying into a Category 1 hurricane just before landfall, though, and our two best statistical intensity models, the DSHIPS and LGEM models, had TD 9 as a borderline tropical storm/Category 1 hurricane at landfall. NHC is going with a forecast of a 65 mph tropical storm at landfall, noting that increasing wind shear in the final day before landfall may stop the intensification process. TD 9 could be a Category 1 hurricane at landfall, as suggested by our best intensity models, and residents along the Gulf Coast of Florida should anticipate this possibility. This portion of the coast is highly vulnerable to large storm surges, due to the extensive stretch of shallow continental shelf water offshore that extend up to 90 miles from the coast. A worst-case Category 1 hurricane hitting at high tide can cause a storm surge that will inundate the Florida Gulf Coast north of Tampa to a depth to 9 - 10 feet, as seen in SLOSH model imagery available in WU’s storm surge pages.

NOAA/RAMMB has some impressive rapid scan loops of TD 9 with images taken every minute.

TD 8 headed for the Outer Banks of North Carolina
A Tropical Storm Watch is up for the Outer Banks of North Carolina as Tropical Depression Eight churns northwest at 7 mph towards the state. TD 8 has not strengthened into a tropical storm yet, confirmed an Air Force hurricane hunter aircraft on Monday morning, as the plane found top winds in the storm near 35 mph, with a central pressure holding steady at 1011 mb.

Figure 3. Latest satellite image of Tropical Depression Eight.

Satellite images on Monday morning showed TD 8 had a vigorous circulation but only a meager amount of heavy thunderstorms. The depression was not developing due to very dry air (45 - 50% relative humidity at mid-levels of the atmosphere), combined with moderate wind shear of 10 - 20 knots. Sea surface temperatures (SSTs) near TD 8’s center remained favorable for development, though, near 29°C (84°F).

Forecast for TD 8: grazing the Outer Banks of North Carolina
The computer models are in excellent agreement that TD 8 will continue on its current northwest track through Tuesday morning, then make a sharp turn to the north and northeast on Tuesday afternoon after getting caught in the steering flow of a trough of low pressure passing to the north. These steering currents should bring the center of TD 8 very close to Cape Hatteras, North Carolina on Tuesday night. A storm surge of 1 - 2 feet can be expected along the Outer Banks, along with heavy rains of 1 - 3 inches. In their 11 am EDT Monday Wind Probability Forecast, NHC’s highest odds for getting tropical storm force winds of 34+ mph from TD 8 were 46% for Cape Hatteras, North Carolina. Dry air and moderate wind shear will continue to affect TD 8 through Wednesday, and it is unlikely this storm will be stronger than a 50 mph tropical storm at the time of its closest approach to the coast on Tuesday night. As TD 8 accelerates away from the coast on Wednesday and Thursday, more significant strengthening may occur.

A new tropical wave worth watching is leaving the coast of Africa
A large tropical wave with plenty of spin will emerge from the coast of Africa late on Monday, move through the Cabo Verde Islands on Tuesday, and potentially develop into a tropical depression later in the week as it heads west at 15 - 20 mph across the tropical Atlantic. The latest runs of our three top models for forecasting tropical cyclone genesis, the GFS, ECMWF and UKMET models, continue to agree that this wave will develop into a tropical depression late in the week. The wave should remain on a fairly straightforward west to west-northwest path through the week, arriving near or just north of the Lesser Antilles Islands by Sunday evening. In their 8 am EDT Monday Tropical Weather Outlook, NHC gave this disturbance 2-day and 5-day development odds of 0% and 50%, respectively.

Figure 4. Visible satellite image of Hurricane Gaston as of 1415Z (10:15 am EDT) Monday, August 29, 2016. Image credit: NOAA/NESDIS.

Powerful Gaston loiters over the remote Atlantic
Hurricane Gaston continues to aim its formidable power on the open Atlantic, about 600 miles east of Bermuda, rather than on people and structures. After peaking early Monday with top sustained winds of 120 mph, Gaston weakened slightly, but it remains a strong Category 2 hurricane with top winds of 110 mph in the 11 am EDT Monday NHC advisory. Gaston’s show of strength is remarkable given that it is practically parked over the remote subtropical Atlantic: it has moved less than 100 miles in the 24 hours ending at 11 am EDT. Hurricanes moving this slowly are often weakened as they churn up cooler water--but the western subtropical Atlantic is remarkably warm this summer, with SSTs of 29°C (84°F) near Gaston more than 1.5°C above average. Currently drifting north at just 2 mph, Gaston has another day or so of favorable conditions before a North Atlantic trough bumps up the currently-light wind shear and begins accelerating Gaston toward the northeast and toward cooler waters. It will likely hold its own for several days, though, perhaps remaining a hurricane till Thursday or Friday.

Gaston is on track to sweep over or near the Azores this weekend. The 5-day NHC outlook puts Gaston close to the northern Azores as a 60-mph tropical storm on Saturday, September 3. The Azores see a tropical cyclone landfall only about once a decade on average, although the nation was struck this past January by the bizarrely out-of-season Hurricane Alex. The islands have never recorded two landfalls in a single year.

Figure 5. GOES-West infrared image of Hurricanes Madeline (center) and Lester (right), both moving west toward Hawaii (left). Image credit: NASA/MSFC Earth Science Office.

Will the Fujiwhara effect keep Hurricanes Madeline and Lester away from Hawaii?
Amazingly, two hurricanes are rolling across the North Pacific, one behind the other, on tracks aiming toward the seldom-struck Hawaiian islands. Either one could make landfall in the next week--but it’s also possible that an obscure atmospheric mechanism will kick in just in time to steer one or both of them away from the 50th state.

Hurricane Madeline is the more immediate threat. As of the 11 am EDT Monday advisory from the Central Pacific Hurricane Center, Category 2 Madeline was located about 700 miles east of Hilo, HI, moving west-northwest at 10 mph with top sustained winds of 100 mph. Madeline has been getting stronger over the past day, with a broadening shield of convection and an eye intermittently visible. It’s not out of the question that Madeline will become a major hurricane by Tuesday, with wind shear very low (around 5 knots) and SSTs of 26-27°C. Somewhat drier air and increasing wind shear will begin affecting Madeline by midweek, with gradual weakening expected. The official CPHC track takes Madeline on a west-southwest arc, brushing the Big Island on Wednesday night as a Category 1 storm. At its closest, the center of Madeline is projected to be roughly 100 miles south of Hilo--which is smaller than the average three-day track error of 130 miles in this region. The upshot is that the first-ever recorded hurricane strike on the Big Island is within the realm of possibility. Even if Madeline stays south of the Big Island, very strong northeast winds rotating around the hurricanes could produce torrential rains and flooding on the east side of the island.

Hard on the heels of Madeline is even-stronger Category 3 Hurricane Lester, which on Monday become the fourth major hurricane of the 2016 East Pacific season. Packing top sustained winds of 125 mph as of the 11 am EDT Monday advisory, Lester is showing signs of evolving into an annular hurricane--the type that features a large eye and convection concentrated in a single ring around that eye, rather than in spiral bands. Annular hurricanes tend to be slow to weaken, and Lester shows no signs of weakening in the near future. Wind shear will remain less than 15 knots for the next several days, with SSTs around 26-27°C adequate to keep Lester going. NHC predicts that Lester will be about 150 miles northeast of Hilo on Saturday morning as a Category 1 hurricane, on a northwestward-angling track that could keep the storm just north of the islands. Lester is now moving west at 14 mph, bringing it gradually closer to Madeline.

Figure 6. The Fujiwhara effect causes two tropical cyclones near each other to rotate around a common midpoint. This motion is on top of the preexisting movement of each cyclone. Image credit: Hong Kong Observatory.

Ironically, the coexistence of Madeline and Lester may help keep either one from a direct landfall on Hawaii, thanks to the Fujiwhara effect, which was discovered nearly a century ago by Japanese researcher Sakuhei Fujiwara. When two tropical cyclones get within about 800 miles of each other, the interaction tends to make the pair rotate around a common point in between, with the effect superimposed on the storm’s preexisting motions. In a case like this, the easterm storm (Lester) would angle northward and the western storm (Madeline) would angle southward. Both effects would tend to angle Madeline and Lester away from Hawaii.

Hurricanes and tropical storms are getting more common around Hawaii
The prospect of two potential Hawaiian landfalls in one week is an exceptional event, since tropical storms are so rare in the state. Only five tropical storms have struck since records began in 1949, and two of those have been in the last three years:

--Hurricane Darby made landfall along the southeast shore of Hawaii’s Big Island on July 23, 2016, as a minimal tropical storm (top sustained winds of 40 mph). Damage was minimal and there were no deaths from Darby.

--Tropical Storm Iselle, which, like Darby, made landfall along the southeast shore of the Big Island, arriving as a 60-mph tropical storm on August 8, 2014. Iselle killed one person and did $79 million in damage.

--Hurricane Iniki, which hit Kauai as a Category 4 hurricane, killing 6 and causing $1.8 billion in damage (1992 dollars.)

--Hurricane Dot, which hit Kauai as a Category 1 hurricane, causing 6 indirect deaths and $6 million in damage (1959 dollars.)

--An unnamed 1958 storm that had sustained winds of 50 mph at landfall on the Big Island. The storm killed one person and caused $0.5 million in damage.

The region around Hawaii has seen a lot of tropical activity over the past four years, including a number of near-misses. Partly this is a result of El NiƱo, which warmed the waters of the tropical Central and Eastern Pacific where Hawaii-heading cyclones are born. However, the uptick may also be a harbinger of things to come. See the August 2014 post, Climate Change May Increase the Number of Hawaiian Hurricanes.

Figure 7. Tracks of all tropical cyclones (tropical depressions, tropical storms, and hurricanes) to pass within 100 miles of the Hawaiian Islands, 1949 - 2016. On July 25, 2016, Tropical Storm Darby made the closest approach on record by a tropical storm to Honolulu, passing just 40 miles to the south and west of Hawaii’s capital with sustained 40 mph winds. Darby brought torrential rains in excess of ten inches to portions of Oahu. Image credit: NOAA/CSC.

We'll be back with updates as conditions warrant.

Jeff Masters and Bob Henson

Weather Underground National Forecast for Monday,August 29,2016

By: nationalsummary , 6:34AM,GMT on August 29,2016

Weather Underground Forecast for Monday,August 29,2016

Active weather will affect a large portion of the Plains on Monday, while dry conditions persist across areas west of the Rockies.

A cold frontal boundary will extend southwestward from south central Canada to the upper Intermountain West. This frontal system will drift southeastward, colliding with warm and humid air over the central third of the country. This interaction will lead to showers and thunderstorms across portions of the northern Plains, the central Plains and the upper Midwest. Just to the east, an area of low pressure will transition eastward across southeast Canada. A cold frontal boundary extending southward will initiate showers and thunderstorms over parts of the Ohio Valley, the interior section of the northern Mid-Atlantic and New England.

Meanwhile, a tropical disturbance will make its way west northwestward over the eastern edge of the Gulf of Mexico. This system will carry rain and thunderstorms over a large span of the Florida Peninsula. Areas in southern Florida could receive between 1 to 2 inches of rain on Monday. Another tropical disturbance will keep stormy weather in the picture for the central and western Gulf Coast, as well as the southern Plains. Some areas along the Gulf Coast may receive anywhere from 2 to 4 inches of rain.

Daytime heating will continue to trigger monsoonal thunderstorms across Colorado and New Mexico. Most states west of the Continental Divide will stay clear of precipitation on Monday. Temperatures will spike several degrees above normal across the Desert Southwest as high pressure builds over the eastern Pacific.

This Date in Weather History for August 29,2016 from

Weather History
For Monday,August 29,2016
1962 - Hackberry, LA, was deluged with twenty-two inches of rain in 24 hours, establishing a state record. (The Weather Channel)
1965 - A national record for the month of August was established when 2.5 inches of snow fell atop Mount Washington NH. Temperatures in New England dipped to 39 degrees at Nantucket MA, and to 25 degrees in Vermont. For many location it was the earliest freeze of record. (David Ludlum)
1987 - Some of the most powerful thunderstorms in several years developed over the piedmont of North Carolina, and marched across central sections of the state during the late afternoon and evening hours. Baseball size hail was reported around Albemarle, while thunderstorm winds downed giant trees around High Falls. (The National Weather Summary) (Storm Data)
1988 - Cool air invaded the north central U.S. Ten cities reported record low temperatures for the date, including Bismarck ND with a reading of 33 degrees. Deerfield, a small town in the Black Hills of South Dakota, reported a low of 23 degrees. The remnants of Tropical Storm Chris drenched eastern Pennsylvania with up to five and a half inches of rain, and produced high winds which gusted to 90 mph, severely damaging a hundred boats in Anne Arundel County MD. (The National Weather Summary) (Storm Data)
1989 - Evening thunderstorms produced destructive lightning in West Virginia. The lightning caused widepsread damage, particularily in Doddridge County. Numerous trees were downed closing many roads. Fire companies had a difficult time tending to the many homes and trailers on fire. Anchorage AK reported a record 9.60 inches of rain for the month of August. The average annual precipitation for Anchorage is just slighty more than fifteen inches. Three day rainfall totals in northwest Missouri ranged up to 8.20 inches at Maryville. (The National Weather Summary)
2005 - Hurricane Katrina made landfall in Plaquemines Parish in southeastern Louisiana early on the 29th with maximum sustained winds near 125 mph, a strong category-three, and the third most-intense landfalling hurricane in U.S. history. The center of the hurricane passed just east of New Orleans, where winds gusted over 100 mph. Widespread devastation and unprecedented flooding occurred, submerging at least 80 percent of the city as levees failed. Farther east, powerful winds and a devastating storm surge of 20-30 feet raked the Mississippi coastline, including Gulfport and Biloxi, where Gulf of Mexico floodwaters spread several miles inland. Rainfall amounts of 8-10 inches were common along and to the east of the storm's path. Katrina weakened to a tropical storm as it tracked northward through Mississippi and gradually lost its identity as it moved into the Tennessee Valley on the 30th, dum