Subtropical system may develop in Atlantic

A broad area of low pressure northeast of Bermuda, in the North Atlantic, has a chance to develop into a subtropical system as it moves west-southwest over the next few days. The area of low pressure will begin to strengthen as it moves into a favorable environment with less wind shear and warmer ocean temperatures.

This environment may allow for a brief window of intensification into a subtropical system, possibly becoming the first subtropical storm of the season. The National Hurricane Center gives this broad area of low pressure a 90% chance for development into a subtropical system over the next five days.

If this system develops, it would become Ana. ‘Ana’ is expected to eventually turn north, moving into cooler waters and an atmosphere with high wind shear. This will quickly weaken ‘Ana’ and keep the system from impacting the U.S. Keep in mind, the 2021 Atlantic Hurricane Season begins June 1st.

Gulf of Mexico and Atlantic Tropical Outlook for the upcoming week

May 15th marks the first day of the National Hurricane Center (NHC) issuing routine tropical outlooks for the Gulf of Mexico, North Atlantic, and Caribbean Sea. The NHC is not expecting tropical cyclone formation during the next five days.

While the NHC is not forecasting any development of tropical cyclones over the next five days, numerical guidance has hinted at the possibility of tropical or subtropical development in the northern Gulf of Mexico in about seven days. The chances of this are low, but it is something to keep an eye on for the Gulf States. If a system were to develop, it would likely be unorganized and weak. However, May system can be efficient rain producers. This will be monitored over the coming days so keep checking back for updates.

Keep a close eye on the Gulf as May is growing increasingly tropically active

The Gulf of Mexico water temperatures continue to slowly increase as we move closer to Summer. Temperatures have risen into the 70s and 80s, which is a touch above average for the majority of the Gulf. The one exception is just off the coast of Mississippi, Alabama, and the Florida Panhandle where water temperatures are running a tad below average.

Overall, however, temperatures have recovered quite a bit from the February Arctic outbreak. The cold outbreak led to water temperatures significantly below average across the northwestern Gulf of Mexico to start Spring. This undoubtedly had a drastic impact on severe weather across the Plains. The water temperatures, as aforementioned however, have finally recovered.

This is a growing concern because we are just days away from the start of the Atlantic Hurricane season, which starts June 1st. Cold fronts that move south, will have the capability to stall over the norther and central Gulf of Mexico over the next couple of weeks, leading to the development of tropical cyclones.

Despite the official June start date, May cannot be slept on. In 2020, there were two preseason storms. Arthur developed in the middle of May while Bertha developed during the end of May. Over the past decade (2011-2020), ten preseason storms have developed, which is the most in modern record-keeping.

The 2021 Atlantic Hurricane Season is forecast to be above average. This coming off the most active hurricane season on record with 30-named storms and 6 hurricanes hitting the United States. One of the most well-known and prestigious outlooks was released several weeks ago. Colorado State University announced its 2021 Atlantic basin seasonal hurricane forecast and is expecting an above average season with 17 named storms, 8 hurricanes and 4 major hurricanes. A major hurricane is classified as a Category 3 or stronger. What is most concerning about the forecast is that experts anticipate an above average probability for major hurricanes making landfall along the U.S. coastline and in the Caribbean. 

Tropical Storm Andres develops, plus Atlantic Hurricane Season outlook

Tropical Storm Andres developed in the eastern Pacific Sunday morning. This is the earliest Tropical Storm to develop in recorded history in the eastern Pacific. The system is expected to remain over water and eventually weaken. This is a good reminder that the Atlantic Hurricane Season is right around the corner.

The 2021 Atlantic Hurricane Season begins in just under a month, on June 1st. It is time to begin talking about the tropics and preparing for the upcoming season. Despite the official June start date, May cannot be slept on. In 2020, there were two preseason storms. Arthur developed in the middle of May while Bertha developed during the end of May. Over the past decade (2011-2020), ten preseason storms have developed, which is the most in modern record-keeping.

The frequency of tropical cyclones steadily climbs from May to September 10th. Due to the frequency of tropical activity developing prior to June 1st, the National Hurricane Center will begin issuing tropical outlooks on May 15th. 

The 2021 Atlantic Hurricane Season is forecast to be above average. This coming off the most active hurricane season on record with 30-named storms and 6 hurricanes hitting the United States. One of the most well-known and prestigious outlooks was released several weeks ago. Colorado State University announced its 2021 Atlantic basin seasonal hurricane forecast and is expecting an above average season with 17 named storms, 8 hurricanes and 4 major hurricanes. A major hurricane is classified as a Category 3 or stronger. What is most concerning about the forecast is that experts anticipate an above average probability for major hurricanes making landfall along the U.S. coastline and in the Caribbean. 

One of the main factors favoring an above average season is the absence of El Niño. El Niño tends to create a hostile environment over the tropical Atlantic, disrupting the development and strengthening of tropical cyclones. Without El Niño, this favors an above average Atlantic season. Another factor favoring an above average season is warmer than average sea surface temperatures across the basin, especially near the main development region. Parts of the Atlantic ocean are 0.5-degrees warmer than average. Warm sea surface temperatures aid in the development and strengthening of tropical cyclones, which will help boost the numbers above average this season. 

Earlier this year, the northern and western Gulf of Mexico water temperatures were running below average due to the Arctic outbreak in February. Those temperatures have slowly recovered throughout March and April and are not expected to mitigate the numbers this season.

The 2021 forecast from CSU is slightly higher than their forecast last year. Their 2020 forecast predicted 16 storms, 8 hurricanes and 4 major hurricanes. The 2021 forecast from CSU will be revised at the beginning of June. Go ahead and begin preparing for hurricane season now. Create your hurricane kit and make sure your insurance is up-to-date.

Gulf of Mexico water temps to have big impacts on severe thunderstorms this spring

The northwestern Gulf of Mexico is still recovering from the February Arctic intrusion that impacted Texas. As of early-March, water temperatures are well below average. The below average water temperatures will undoubtedly have an impact on convection and severe thunderstorms west of the Mississippi throughout March.  

Current Gulf of Mexico Water Temperature

The Gulf of Mexico waters are an important variable in convection and severe thunderstorms for areas east of the Rockies. Generally speaking, when the Gulf of Mexico water temperatures are above average, this leads to more instability for convection and severe thunderstorms by supplying the atmosphere with added moisture and warmth. Instability acts as fuel for thunderstorms, and many times, the greater the instability, the stronger the thunderstorm if other variables are favorable. Thus, the added moisture and warmth bolsters instability, creating increased severe thunderstorms. 

Research shows the warmer the Gulf of Mexico water temperatures, the more hail and tornadoes occur throughout March, April, and May. With the water temperatures running below average in the northwestern Gulf of Mexico, it is possible this will have implications on convection and severe thunderstorms throughout the month of March due to the decreased availability of moisture and warmth added to the atmosphere. This may lead to less intense convection or a decrease in tornado and large hail frequencies during the month of March for areas west of the Mississippi River. It should be noted: severe thunderstorms are still possible throughout March but the frequency and intensity may be impacted. Areas farther east into Dixie Alley and the Southeast will likely not see a decrease in thunderstorm intensity and frequency as Gulf of Mexico water temperatures are above average in the eastern-half of the Gulf.

Above average temperatures are forecast for the region throughout March so this will allow the Gulf of Mexico water temperatures to slowly recover, possibly returning to average or even climbing above average by April, which could lead to an increase in severe weather during April and May.  

March Temperature Outlook

Hurricane Willa’s Remnants Will Have Large Impacts From Gulf States And Up The East Coast

Hurricane Willa is getting closer to the west-central coast of Mexico and should make landfall within the next few hours (Tuesday evening). Willa should retain major status until landfall. Willa will begin to weaken and lose its tropical characteristics as it moves across the higher terrain of Mexico into Texas but the remnants will remain well established to have large impacts from mid-week through the weekend for parts of the United States.

As the remnants move into Texas, deep moisture will stream northward throughout Texas into eastern New Mexico and Oklahoma. This will aid in heavy rainfall for this region with the greatest flood threat occurring in central and southern Texas, which has recently been inundated with rain. Widespread 1-3″ amounts are possible in eastern New Mexico and central and southern Texas with isolated 3-4″ amounts in central Texas near the Hill Country (see Fig. 1).

Fig. 1: 7-day rainfall forecast

The remnants will move out of Texas on Wednesday, merge with a shortwave, and begin to slowly intensify across the northern Gulf by Thursday. This will aid in thunderstorms and heavy rain for the Gulf States (from Louisiana to Florida) for late week. The low will then move off of the Southeast coast by late Friday and begin a north-northeastward forward movement off of the coast of the Carolinas. At this point, the low will begin to interact with an approaching cold front and deepen fairly quickly by Saturday morning as it spins off of the coast of the Mid-Atlantic. Heavy precipitation (see Fig. 1), rough seas and strong winds up to 30-60 mph (see Fig. 2)) will be possible for parts of the Mid-Atlantic and Northeast through the weekend. While coastal areas will see heavy rain (2-4″ are possible), areas further inland may see snow.

Fig. 2: Wind forecast Saturday evening

That is right, snow is possible as the nor’easter wraps in enough cold air for a transition to a heavy, wet snow. The best chance for snow will occur in interior parts of the Northeast down into the higher terrain of West Virginia. These areas may see a few inches of wet snow with several inches possible in the higher elevations of the Appalachians. Please keep in mind, we are a few days out so the snowfall forecast will likely need to be adjusted. A couple degrees cooler or warmer will have large impacts on accumulations and precipitation type.

Flooding is possible in Texas from this storm, which will impact travel. Turn around, don’t drown. Travel implications are also likely in parts of the Mid-Atlantic and Northeast due to wind and precipitation. With trees still having leaves on them, this increases the likelihood of them being overwhelmed for either wind or snow. This will increase the chances of power outages in this region over the weekend.

Hurricane Florence Forecast Update – Impacts Begin Tomorrow

Florence remains to be a powerful category 3 hurricane with maximum sustained winds of 120 mph. Some weakening has occurred today, but there will be one last window tonight and early tomorrow for Florence to have another shot at strengthening a bit before its center begins to reach the southern North Carolina/northern South Carolina coasts.

This will be a very brief article on some of the slight modifications that I made to my forecast.

The first image below shows the official track and cone of uncertainty from the National Hurricane Center. Their latest forecast has Florence making landfall along the southern coast of North Carolina before moving into South Carolina. I plotted their forecast on a county map, so that you can see it a bit better.

hurricane florence track

hurricane florence track county map

The Weather Prediction Center’s latest rainfall forecast indicates that 20+ inches of rain will fall along and just inland from the southern North Carolina/northern South Carolina coasts. Some regions could exceed 40 inches of rain. For those in any region that is forecasted to get around or above 4 to 6 inches of rain, take special note. The flooding situation that evolves will be the big story with Florence.

hurricane florence rainfall forecast

I made no changes to my landfall forecast from last night. It’s within the realm of possibilities that Florence could skirt southwest along the South Carolina coast once interacting with land, but I decided not to account for a possible second landfall that might occur. Getting into very technical details likely won’t change the overall impacts anyway.

hurricane florence landfall forecast

I made some modifications to my impacts map. I extended the pink zone, the region where I believe impacts could be severe, farther northeast along the North Carolina coast. Even though a landfall should occur farther southward, high storm surge will likely be very high well-away from the storm’s center to the right. I made no modifications to the pink zone in South Carolina. I’m not confident enough at this point that Florence won’t attempt to make a turn southwestward along the South Carolina coast. If I gain more confidence that for some reason that won’t occur, I’ll modify that part of the forecast tomorrow.

hurricane florence impacts map

Other than that, I trimmed back some of the red zone, the region where I believe at least some impacts could occur, for parts of Virginia. I made some subtle changes across Georgia, Tennessee, and West Virginia to include additional locations. Generally, the red region is where I believe tropical storm-force winds (or gusts) and/or flooding will occur. Since Florence is quite large and will slow significantly, that accounts for some of why that region is so large.

Please stayed updated on Firsthand Weather for future updates.

Hurricane Florence Likely To Be Catastrophic For Parts of the Carolina Coast

After Florence’s recent eyewall replacement cycle, it has re-strengthened into a 140 mph hurricane. Strengthening is expected to continue, given that vertical wind shear will be weak, sea surface temperatures will be more than sufficiently warm, and little dry air will be present to mix into Florence’s core. In an effort to answer many unanswered questions, I’ve made a couple of maps. Let me briefly explain what they mean.

The first map includes where I believe Florence will be making its (first) landfall. Some southern shifts in track could occur; thus, I’ve included the northern South Carolina coast as a potential landfall location. Given the fairly good consistency amongst the models on landfall location, I decided not to shift the landfall threat farther south. I’ll decide tomorrow if I need to make any additional shifts southward. Locations in and around the circled region is where I am currently anticipating damage to reach catastrophic levels.

Hurricane Florence landfall

The second map includes the regions that could be impacted by Florence, whether that’s from wind, flooding, or coastal storm-surge. Most of the forecast model guidance today made a noteworthy shift westward (and even southwestward) in Florence’s track once it reaches the southern North Carolina and northern South Carolina coasts. Some of the guidance even brings the center back over water and has a second landfall occurring farther southward into South Carolina. Weak steering flow is making this a particular challenging forecast. A high pressure ridge to Florence’s east/northeast and also to its west will result in Florence slowing significantly near the coast. The pink zone is where I’m currently most concerned about; while some parts of the red zone could experience significant impacts as well. At the least, I expect those in the red zone to experience some impacts from wind and rain. If the southward trend continues, I may end up chopping parts of northern Virginia out of the red zone, but in this update, I mainly included them due to potential flooding. I’m sure modifications will have to be made to the forecast, since we’re now getting down to the county-level.

Hurricane Florence impact zones

Please continue to follow Firsthand Weather on Facebook and this site for future updates.

“Joyce” to impact Texas?

Firsthand Weather is keeping a very close eye on the convection located over the southeastern Gulf of Mexico and northwestern Caribbean (see Fig. 1). This area of convection will persist over the next 48 hours and should begin to organize by 48-72 hours into Tropical Depression/Storm Joyce. Right now, the upper-level winds are not conducive for organization but these winds will become more favorable by late week. The majority of the European ensemble members are showing development with a northwest movement into southern Texas by Friday (see Fig. 2) and the GFS and Canadian show a decent area of pressure falls (hinting at a Tropical Depression/Storm) in the same vicinity. This is why the National Hurricane Center (NHC) has given this area a 50% chance of development over the next two days and a 70% chance of development by day five (see Fig. 2).

Fig. 1: Convection that may develop into Joyce later this week

Fig. 2: European ensembles

Fig. 3: Area being monitored by the NHC
By late week, what could be Tropical Storm Joyce should be in the western Gulf. This will lead to copious amounts of moisture moving into south and coastal parts of Texas. Widespread 4-8″ of rainfall are possible with the possibility of amounts exceeding 10″ in areas (see Fig. 4). This part of Texas has received above average precipitation as of late, thus, the grounds are saturated; leading to an enhanced flash flood threat for the region from Thursday through the upcoming weekend.

Fig. 4: 7-day rainfall forecast
While a general WNW to NW motion is what is depicted by numerical guidance, much uncertainty does exist with the track of this system. Generally, the consensus of guidance has a landfall between Corpus Christi and South Padre Island. This could deviate further south or further north depending on the strength of the system. A stronger Tropical Storm/Hurricane would likely force a more WNW motion due to the 500mb ridge possibly intensifying to the north whereas a weaker Tropical Depression/Tropical Storm would likely track more to the NW.

Regardless of development into Tropical Storm Joyce, this system will lead to an influx of moisture into parts of southern Texas, which will increase the flood threat. Other hazards associated with this area of disturbed weather for Texas are: rough seas, rip currents and gusty winds. Keep checking back for updates because the waters are warm in this area so if organization occurs faster than expected, it is possible this system could ramp up quickly.

What Impacts Should You Expect From Hurricane Florence?

Hurricane Florence underwent rapid intensification last night and today and currently has maximum sustained winds of 140 mph. This puts Florence at category 4 strength, and expectations are that further strengthening will occur, given the favorable environmental conditions. It appears that Florence’s strength has currently leveled off for the time being, and with hurricanes of this strength, it is not uncommon for an eyewall replacement cycle to occur. This occurs when an outer eyewall begins to form around the original eyewall. Over time, the new eyewall eventually replaces the old one. Although this can result in temporary weakening, the storm can later strengthen further, and the wind field usually increases in diameter. We will have to see if that occurs overnight tonight or tomorrow.

In this article, I want to focus mostly on impacts, instead of going into a lot of detailed meteorology as I often do in my discussions. Below, I have included several questions that many of you have asked, and I am going to do my best to answer those.

Where is Hurricane Florence going to make landfall?

We’ve managed to get a better handle on where Florence is going, even though there are still some disagreements in the forecast model guidance. That’s normal though! Previously, we outlined a region from the northern Florida coast through the Carolinas. That zone can now be narrowed down a bit further. The region that should watch for a potential landfall extends from Charleston, SC to the northern coast of North Carolina. The latest several runs of the operational European model have consistently projected a landfall around the South Carolina/North Carolina border, and the ensemble means have shown a similar picture, maybe a hair farther south. Even though locations as far south as Charleston is out of the National Hurricane Center’s cone of uncertainty, I want to watch this storm for another 12 hours before taking that location out of the threat zone, especially since Florence has continued to maintain a westward to west northwestward trajectory. As ridging begins to build and strengthen to Florence’s north, we’ll see if it begins on a more northwest trajectory tomorrow.

Hurricane Florence forecast

Hurricane-force winds will extend well-inland from the center of the storm and along areas to the east of the center. Florence is going to slow down significantly as it approaches land; meaning, this may put somewhat of a limit on just how far inland hurricane-force wind gusts will extend. If the storm were booking it, it would cover a lot of real estate before weakening. In this case, hurricane-force winds may ultimately occur over less real estate, compared to a Hugo-type storm, BUT the wind damage that occurs within the first 24-hours of Florence’s landfall could very well reach catastrophic levels. Given that even a small margin of error in track could change the region that will have those kinds of winds, I recommend erring on the side of caution and preparing, especially if you’re on the Carolina coastline and within 100 miles of the coast.

Hurricane Florence winds

How much flooding will Florence produce, and how widespread will it be?

If Florence makes landfall where it is currently projected, flooding could be widespread and deadly, well away from the storm’s center. Air will be forced upward by the mountainous terrain on the eastern side of Florence, something referred to as orographic lift. This means that rainfall rates could be a bit higher compared to a region that has a hurricane moving over flat terrain. Remember, Harvey was a prolific rain producer because it stalled for days. There will be other factors at play that could enhance Florence’s total rainfall amounts; thus less time will be needed for heavy rainfall totals to occur.

In no way do I want to undermine the wind threat. It’s going to be bad! But, I always take flooding very seriously on Firsthand Weather, especially when I see that it’s going to be a widespread event such as this one. Below, I included an image that shows the Weather Prediction Center’s current projected rainfall totals that will be associated with Florence. As you can see, widespread areas of 10 to 15 inches of rain is expected across North Carolina and Virginia. Many of those locations have already received a lot of rainfall this summer, even recently. I think these totals could be a bit underdone in some places, so assume that there will be regions that could well-exceed above 10 to 15 inch rainfall totals.

Hurricane Florence rainfall

Will Storm Surge Be A Big Threat?

The short answer is. . .yes!! For residents along and near the coast, storm surge will be a major issue on the east side of Florence. This is a deadly threat that is often not taken seriously. Even a very small change in track could alter the regions that will get the highest storm surge.

Hurricane Florence storm surge

Some Advice:

If you are under mandatory evacuations, I strongly urge you to evacuate. There will be some of you who will evacuate and may come to realize by the end of all of this that it wasn’t necessary. However, you don’t want to find yourself in a situation wishing that you had left. You may be putting yourself and your family at risk. It’s generally a good idea to expect the unexpected. When do meteorologists ever get a forecast completely accurate, especially one like this? Never. That’s not a criticism of the science, but instead, it’s something that you should take into consideration. It’s best to plan for unexpected changes in track and intensity that weren’t necessary predicted by professional meteorologists. It’s the nature of the science, and it’s one you should be aware of, especially if you are tempted to believe your area may not be a high-impact area.

If you are unable to evacuate, whether that’s due to financial reasons or whatever else, try to reach out to those who are willing to help. Many of our followers on Firsthand Weather have been providing tips, making others aware of resources that they weren’t aware of, and even offering their homes for free for others to stay. Please go to the Firsthand Weather Facebook page, and we will do our best to guide you to the great amount of information that many of our followers have already provided.