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 Irma Set To Impact Leeward Islands, Puerto Rico, Hispaniola, and Cuba

As of 8 pm ET, Hurricane Irma has maximum sustained winds of 185 mph with gusts reaching 225 mph. After undergoing rapid intensification, Irma has maintained its strength and is now one of the strongest hurricanes ever recorded in the Atlantic. It is the strongest Atlantic hurricane ever recorded outside of the Gulf of Mexico and Caribbean Ocean, and if its sustained winds increase to over 190 mph, Irma will officially become the strongest hurricane ever recorded in the Atlantic. While sustained winds did not increase between the 5 and 8 pm advisories, the pressure dropped from 926 to 916 millibars.

Infrared hurricane irma
Figure 1: Latest infrared imagery of Hurricane Irma

Firsthand Weather will be coming out with a detailed article on Hurricane Irma tomorrow evening (Wednesday evening) at 8 pm. This will be one of my more in-depth articles on this system, and I encourage everyone to be on the website around that time. I’ll be discussing potential impacts, track, etc.

Hurricane Irma Track
Figure 2: Hurricane Irma latest projected path

Hurricane Irma is steadily moving westward towards the Leeward Islands, which will be the strongest hurricane to have ever impacted that region (since records have been kept). Antigua and Barbuda are first in line to be heavily impacted by Irma, and overall, conditions will deteriorate considerably, particularly across the northern Leeward Islands, as the night progresses. From this point onward, Irma will trek along the northern parts of Puerto Rico, Hispaniola, and Cuba. Conditions, especially over northern/northeastern Puerto Rico, will decline over the course of tomorrow, and if this system were to trek just slightly farther south than currently projected, impacts will be much worse. Of particular interest in the short-term will be to see how closely Irma tracks to Hispaniola, given that this mountainous island is notorious for rapidly weakening tropical systems. On the downside, a hurricane of this magnitude would devastate those islands, and we don’t want that to occur either. The Bahamas will need to closely monitor Irma towards the end of the week, and then the focus will shift entirely to impacts on the United States.

I know that this was a much less detailed article than what is typical to come from me, but again, I will be releasing a very detailed forecast tomorrow evening at 8 pm ET.

Irma Is So Intense It Is Registering As Earthquakes

Hurricane Irma is now a category 5 hurricane with sustained winds of 185 mph according to the National Hurricane Center. This is one of the strongest hurricanes in recorded history in the Atlantic. In fact, Irma is so strong that the hurricane is registering as earthquakes on seismometers (equipment that measures earthquakes) in Guadeloupe.

So why is this happening? According to Stephen Hicks (a seismologist at the University of Southampton), noise caused by the high winds and the movement of trees-transferring energy into the ground registers as low-pitch sounds that show up as small earthquakes. Some of the seismometers are also located close to the shoreline and can become contaminated (false earthquakes) by large waves generated by Irma. The frequency of the ‘earthquakes’ will increase as Irma nears land and grows in intensity.


Tweets from Stephen Hicks about Irma registering as earthquakes

It should be noted, Irma is not causing actual earthquakes. Earthquakes occur below the surface and there is no research showing a correlation between tropical cyclones and earthquakes. During intense tropical cyclones, it is common to see seismometers register earthquakes due to the winds associated with the tropical cyclone.

Please check back this evening for an updated forecast on Hurricane Irma.

Hurricane Safety and Quick Tropical Update

Hurricane Hunter aircraft are once again in the air this afternoon exploring Hurricane Irma. Yesterday evening, the NOAA and US Air Force put on a display with 4 flights into Irma to gather data. At the moment, there is currently 1 flight under way, an upper level dropsonde mission, but 1 low level recon mission has just completed with more preparing to get under way. Hurricane Warnings are in effect for several of the Caribbean Islands and a very dangerous situation will be occurring there in the next 24 hours. Hurricane watches have been extended to the Turks and Caikos and Southern Bahamas. Irma still has winds of 185 miles per hour with gusts over 220 miles per hour.

Tropical Storm Jose has formed to the East of Irma in the Atlantic. This storm is expected to become a hurricane to be just east of where Irma presently is in about 3 days but the forecast calls for it to move to the Northwest and be less of a threat to the Leeward Islands.

Tropical Depression 13 has formed in the Gulf of Mexico. This is expected to become Tropical Storm Katia in the next couple of days. This system does not appear to be a threat to Texas and will actually loop around to the south and hit Mexico at this time. We will obviously watch this situation carefully.

The track below are Irma, Jose and 13 respectively.

Hurricane

Hurricane Safety

Evacuations

Evacuation orders are being prepared for in the Florida Keys currently. For those who are evacuating, you will need to determine a safe evacuation route inland and as far north as you can get. While evacuating, you’ll want to monitor the latest information to ensure that you will be evacuating to a location that is not also under a risk. Public services in these areas will already be strained and adding many evacuees will only cause more strain for everyone. Learning the location of official shelters will be helpful both in the event that you evacuate as well as for those who do not evacuate. Areas that are not under evacuation orders should also have shelters for the residents who end up in trouble due to hurricane hazards. Tornadoes, lightning, power outages, and property damage due to falling trees can force residents from their homes, even if a mass evacuation isn’t needed.
When evacuating, put together a go-bag. Include a disaster supply kit, including a flashlight, batteries, cash, first aid supplies, medications, and copies of your critical information if you need to evacuate. Ensure that you secure your critical information in waterproof bags. Snacks and stuff to drink will also be good for longer evacuations, especially with children and pets. While you may stop for gas, many others are also evacuating with you so its possible that many supplies will be sold out along your route. If you haven’t already, fill up your gas tank in your local area. Cell phones should be charged before you leave. Have one member of your family turn their phone off while travelling together. This will ensure that if one phone does run out of battery, you will have another phone to turn on and use. All family members should have all numbers for your phones and know to call multiple numbers if they can’t get a hold of you.
You should also inform someone of your plans. If you fail to arrive at your destination due to a car accident, your contact can alert the authorities. Having them know the route you planned to take is essential in locating you.
Stay tuned to local news outlets as you travel. Conditions may change and areas you were heading to that were going to be safe may not be anymore. Harvey brought a large area of rain to Texas and some locations people were heading for wound up under a flood warning when it wasn’t before. Always ensure that the safety of your location is the top priority.

Staying at home

For those of you who are not leaving home, I would first implore you to heed local evacuations if you are under them. Evacuation orders are given for a reason. If you are under those orders it is absolutely not safe where you are. While I do realize that some properties remain even in massively damaged areas, you only put yourself and those who would need to rescue you in the event of an emergency in danger by taking that gamble. It is never just your survival on the line.
If you have not been ordered to evacuate, there are several things you should plan for. First, as I mentioned above, have a plan to be able to evacuate to a local shelter if your house if one of the unfortunate locations that falls victim to one of the more local hurricane hazards. Lighting occurs frequently within a hurricane and can strike even in areas where hurricane conditions are not occurring. You should also have a plan for any pets you may have. Not all shelters accept pets so ensure the one you may go to does.

What to bring to the shelter

You will need to make sure that you have everything you need at the shelter. While the shelter will have supplies, they don’t usually carry specific medications or your specific brand of baby food or pet food. Ensure that you have a first aid kit with all the medications taken by your family. If you are running low, see if your local pharmacy can give you more. Baby food and diapers will be needed. Your baby should be prepared for a multiple day stay at the shelter. Bring things to do as well. Books, games for children, headphones and a source of music (we all know some of you still have a Walkman) will all be desired. The shelter is not exactly a fun place to be. Bring your toiletries and blankets. The shelter will have some but we all prefer our own. Flashlights and batteries are good to have in case the power goes out at the shelter as well. Also ensure you bring identification, cash and credit cards as well as copies of your essential documentation like proof of insurance.

Protecting your home

Be aware that Hurricane winds can cause trees and branches to fall, so before a hurricane trim or remove damaged trees and limbs to keep you and your property safe.
Secure loose rain gutters and downspouts and clear any clogged areas or debris to prevent water damage to your property. This can also help keep them lighter and not fall under the weight of all the rain. Hurricanes can be a daunting experience for a lot of people and if you decide to stay in your home, you need to make sure that all of the exterior systems like your guttering are working efficiently. Too much water in your gutters can increase the chances of water damage, which can result in further problems that you don’t need. By contacting someone similar to this Clean Pro Gutter Cleaning Baltimore company regularly can help to make sure that your gutter is free from anything that could have an impact on how it works, especially in the event of a hurricane. Reduce property damage by retrofitting to secure and reinforce the roof, windows and doors, including the garage doors. Plywood over windows or close storm shutters if your house has them, this can protect them from wind and debris. If you are construction inclined, hurricane clips can be installed in your attic to help secure your roof to the house. You can also brace your garage door and doors that lead outside with planks to keep it from blowing in. You should also close all interior doors to compartmentalize the house. If your doors sustain any damage remember to contact a company like Spark Garage Doors – Repair & Installation straight away. This way, if a window does break in one area, the remaining areas will have protection against the elements coming in. Purchasing a portable generator or installing a generator for use during power outages is also a good idea. Remember to keep generators and other alternate power/heat sources outside, at least 20 feet away from windows and doors and protected from moisture. You should never try to power the house wiring by plugging a generator into a wall outlet. If power does go out, use a flashlight. Candles are a fire hazard.

Keeping food and water safe

The most important thing when it comes to food is to buy nonperishable goods and to store water. You do not need to buy multiple gallons of water for activities like brushing your teeth. Simply refill an old milk or water bottle with tap water and use it. You can do the same thing for bath water, pre-filling your tub is also recommended. Tap water storage can be done with any container from large pots used for cooking to old bottles and even any large plastic container. Always remember to keep using the tap water until it goes out, you don’t want to needlessly use up your supply and not be able to replenish it. For any cold food you do have, turn your refrigerator and freezer to their maximum cold settings and open them as little as possible. This will help keep things cold. Try to use up any chilled foods first so that keeping things cold becomes unnecessary and have a supply of ice on hand to keep things cold longer. While you can buy ice at the store, you can also just use ice cubes. Simply dump your tray into a plastic bag and refill the trays. Dump new ice cubes as they form and keep refilling the trays. You will be able to continue this process for as long as you have power or tap water. This also creates an emergency water supply should you run out of water. Simply melt the ice. You can also use rain water if you have a safe way to get a bucket outside to collect some. You should always try to keep a lid on your water supply. This will keep dust and bugs out of it.

After the Storm

It will be tempting to go outside after the storm has passed or during the calm period in the eye. This should be avoided. The eye is only temporary and hurricane conditions can start very quickly. After the storm, there will be a lot of damage in the region. Floods could still be occurring and the water could be contaminated. You also can’t see what’s in the water. Animals and hazards in the water could be potentially dangerous to your health. The water could even be electrically charged from downed power lines.
Even where roads are visible, bridges and roads may no longer be safe for the weight of a vehicle.
Once you are home, check for damage. Ensure there are no downed wires, water or gas leaks, or damaged appliances in the home. Make sure you get Water Damage and Roofing Austin to repair any damages ASAP to prevent further issues.
We here at Firsthand will do our utmost to keep you up to date with the latest information. Our thoughts go out to those in the areas affected by Harvey. Stay safe everyone.

Robert Millette
Incident Meteorologist
Braintree Emergency Management Agency

Everything You Need To Know About Hurricane Irma

We continue to have a very complex forecast on our hands with Hurricane Irma, and while we do have some time to nail down the forecast, it’s understandable that residents along the East Coast and even along the eastern Gulf of Mexico are wanting to know what plans they should be making in preparation for Irma. Tonight’s article will not be particularly long and detailed, but I do briefly want to point out few things.

As of 8 pm ET, Hurricane Irma is a category 4 hurricane with sustained winds of 120 mph. Irma’s movement is finally back to the west after losing some latitude due to the influence of an upper-level low to the northeast of the system. Bermuda ridging should strengthen in the coming days to the north of Irma and could even build southwest, which will keep system generally on a westward track. Regions, across the northern Lesser Antilles and the Greater Antilles, including Puerto Rico, Haiti, Dominican Republic, and Cuba need to prepare to be impacted by a major hurricane. I have included the National Hurricane Center’s latest five-day forecast, and residents in those regions need to understand that a track just slightly farther to the south will worsen the possible impact from this storm. This could be a serious situation, so again, I urge residents of those islands to not take this threat lightly.

Hurricane Irma Track
Figure 1: The National Hurricane Center’s latest 5-Day forecast for Irma (as of 8 pm ET)

Unlike with Harvey when it first made landfall, Irma’s forecast is quite complex due to the angle that it will be coming towards the coast of the contiguous United States, which could result in a level of uncertainty remaining even by the end of the week or weekend. Additional complicating factors to this forecast include numerous features that will potentially be influencing the track of Irma, which will ultimately determine whether or not this system makes landfall in the U.S. In order to keep this forecast briefer than my last discussion, I’m going to provide a bullet-point list below. I will be providing a follow-up forecast either tomorrow night or Wednesday, depending on how things evolve over the next 18 to 24 hours.

Sea surface temperatures hurricane irma
Figure 2: Irma will continue moving westward into warm waters. The black dot represents Irma’s location as of 8 pm ET.

  • First and foremost, residents across the entire coast of Florida and along the East Coast need to start making some preliminary plans, just in case. In particular, I urge residents from the southern Florida coastline to the Carolina coast to begin making plans and to continue following the forecasts closely. I still can’t rule out this system making it into the far eastern Gulf of Mexico; however, it still remains unlikely. Residents along the western Gulf of Mexico coast do NOT need to worry at this time. If a U.S. landfall occurs, it likely won’t occur until this weekend, at the earliest!
  • A western ridge/eastern trough configuration is going to set up across the United States. If this pattern were to hold, this would allow Irma to safely recurve out to sea away from the U.S. However, this pattern is likely not going to hold long enough. The western ridge is probably going to break (imagine a wave crashing in the ocean), and while the trough could become cut-off from the main flow, it appears that it will move out to the northeast before Irma gets far enough northwest to be picked up. Ridging to the west will remain in place while Bermuda ridging will either build westward or remain in place. Between these two features, a weakness will still be present over the eastern U.S, which will eventually result in Irma taking a sharp turn to the north. The timing of this turn to the north will be everything. It will be the difference between this system going into the far eastward Gulf, through Florida, or impacting regions along the eastern coast of Florida and the Carolinas.
  • Again, this forecast is tricky also because of the angle Irma will be coming in relative to the United States. With Harvey, it moved mostly perpendicular to the coast towards Texas before making its first landfall, so we knew that somewhere along the Texas coast was going to be heavily impacted by hurricane-force winds. In Irma’s case, it will be coming in parallel to the coastline or if it starts making its northward turn south of Florida, it could come in perpendicular to the south Florida coastline (but remember, the southern Florida coastline is MUCH shorter in length than the Texas coastline).
  • At this point, I’m still not ruling out Irma only skirting the coastline or completely being a miss; however, that isn’t the most likely scenario. At this point, the most likely scenario is an impact to Florida, Georgia, and the Carolinas. Keep in mind that modifications to this forecast are likely, and that forecast confidence is much lower than usual.

Hopefully by Wednesday, we’ll get a much clearer picture of what could unfold. Just hang with us, and we’ll make sure we nail down this forecast for you as quickly as possible.

Fake Irma Forecast!

The National Weather Service (NWS) is sending a message to the public after a fake forecast went viral on social media. A Facebook profile with the name “Joe Maley” posted a fake forecast on Facebook, which quickly went viral–receiving more than 37,000 shares. The image shared on Facebook used a National Hurricane Center (NHC) map depicting Hurricane Irma moving towards Texas. This post, which many believed to be authentic, fed into the fears that Texans currently have after being heavily impacted by Hurricane Harvey.

FAKE Forecast Posted On Facebook

The NWS was quick to respond on Twitter today stating: “Keep your eyes out for fake forecasts. THIS is what an official NOAA advisory looks like. Note: forecast only goes out 5 days. #Irma.” The FAKE forecast on Facebook was eventually deleted today.

Statement From NWS

For official forecasts from the NHC, please click HERE!

Keeping A Close Eye on Hurricane Irma

As of 5 pm ET, Hurricane Irma is a category 3 storm (115 mph sustained winds) located at 17.3° N and 34.8° W and is moving west northwest at 12 mph. Irma was only a tropical storm this morning but underwent rapid intensification. Irma has remained in a relatively low-shear environment; however, this kind of quick intensification was actually a bit surprising. While sea surface temperatures were above the threshold for tropical development (above 26°C/79°F) when Irma quickly intensified, these temperatures were not overly warm. While the National Hurricane Center has Irma strengthening further over the next day, I actually wouldn’t be surprised if there is some slight weakening or at the least, no additional strengthening for about a day. There is a bit of dry air out ahead of the system, and as I mentioned, sea surface temperatures are just above the threshold for development. Regardless, Irma will eventually move over much warmer sea surface temperatures (with higher ocean heat content), and given that vertical wind shear should remain light, there’s no reason that this system won’t rapidly intensify into a stronger hurricane, possibly reaching category 4 status over the next few days. To sum it up, after a brief break in strengthening, Irma should strengthen further. If it ends up wrecking homes near you, it might be a smart idea to talk to Ballwin Commercial Roofing Pros to better understand how to repair homes during the aftermath.

dry air hurricane irma

Figure 1: There is some dry air that Hurricane Irma could temporarily encounter.

We are going to be tracking Irma for a long time, which gives us a decent amount of time to figure out where Irma is going. Also, if Irma were to directly impact the contiguous U.S., it won’t be for at least 10 days, give or take a day. It could even be a bit longer. What I’m basically saying is NOT to cancel any plans just yet, but instead, follow the latest tropical updates very closely if you live near the coast or have vacation plans.

Hurricane Irma projected path

Figure 2: The National Hurricane Center’s 5-day projected path of Hurricane Irma

Hurricane Irma Discussion:

The big question over the next several days will be to determine if Irma could be a threat to the U.S. Along with a mid to upper-level low (northwest of Irma) to the south of the Bermuda ridge creating a weakness, numerous shortwave features will ride along the northern periphery of the Bermuda ridge, keeping this ridge on the weaker side over the coming days. In addition to this, the latest guidance indicates that a longwave trough could develop over the eastern U.S. next week. If at this point Irma were to be far enough west, then it would likely recurve and miss the East Coast. However, it appears that the eastern trough will move out in time, and Bermuda high pressure will build westward, possibly extending along the East Coast. This would increase the threat of Irma eventually impacting the East Coast, but also, some guidance builds the Bermuda ridge far enough west and southward that Irma slides between Florida and Cuba into the Gulf of Mexico. At this point, there are a plethora of scenarios, but two of several things to watch closely will be the strength of the Bermuda ridge and how long the longwave trough remains established over the eastern U.S.

If you’re going to follow the forecast models, don’t actually be too focused on where the models show Irma going at this point. The model guidance will continue to vary quite a bit on exact track, so as stated above, the focus should be on the following two features: the strength of the Bermuda ridge and the longwave trough that will be building over the eastern U.S. Also, keep a close eye on how far north Irma gets over the next several days, because a more northward track increases the odds of either impact to the East Coast OR a recurvature out to sea. If the trough fully moves out and Bermuda ridging builds westward quickly enough, then we potentially have a problem in the Gulf of Mexico.

From the looks of it, Typhoon Sanvu in the western Pacific may play a major role in influencing the downstream pattern over the U.S. in about a week. Sanvu is going to gain latitude with time and make an extra-tropical transition as it gets absorbed into the westerlies. Recurving typhoons in the western Pacific can sometimes cause the jet stream to buckle as excess amounts of latent heat gets transferred to the atmosphere, resulting in a wavy jet stream downstream over the U.S. I suspect this is the cause of the western ridge/eastern trough pattern that will evolve over time, and while this would be a great pattern for steering hurricanes away from the U.S. (assuming the hurricane remains high enough in latitude), the forecast model guidance just doesn’t have this pattern sticking around long enough. Some models lift the trough out quickly but leave a piece of energy behind over the southern U.S., and some fully lift out the trough. The problem is that as soon as this trough moves out, the Bermuda ridge will most likely build westward and become well-established. That’s what we don’t need to happen.

Jet stream hurricane irma

Figure 3: Model guidance shows a western ridge/eastern trough configuration over the U.S. next week.

Bullet Point Summary Of “Stuff” To Watch Over The Next 5 to 7 Days:

  • Watch the strength of the Bermuda ridge and see how the upper level low to the south and extra-tropical systems to the north influence its strength.
  • Watch to see if Irma gains some latitude, given that any amount of latitude gain could increase the chance of an East Coast impact OR a recurvature out to sea.
  • Watch the building trough over the eastern U.S. and see how quickly or slowly it will be moving out of the region.
  • Watch how Typhoon Sanvu influences the downstream pattern in about a week, given that this will probably be the culprit behind the western ridge/eastern trough configuration
  • Understand that models have a difficult time handling such meridional flows (wavy jet stream patterns). Throw a hurricane into the mix, and it gets very complicated.
  • Don’t really bother looking at where the models have Irma going beyond 4 to 5 days at this point in time. Focus on the above bullet points for now.

If you read this article and have come to the conclusion that we have no clue what’s going to occur, then, to an extent, you’d be correct. I could wait several days to write these articles until there is a bit more certainty, but I like to go ahead and introduce the Firsthand Weather audience to what I’m actually watching. I will be referring to features such as the Bermuda ridge, the eastern trough, etc. over the next week to two weeks, so I wanted to go ahead and give everyone a very early introduction to what’s going on. It will only make the forecast better over time and will help all of you with your planning for this potential hurricane.

More Heavy Rain To Houston?

First, I would like to send my good thoughts to Houston and all the other communities and towns that have been impacted by Harvey across Texas and Louisiana. If there is anything Firsthand Weather can do to assist you all, please do not hesitate to send us a message!

The rain has begun to shift eastward to far eastern Texas, and towards Louisiana and Mississippi. This will allow for better weather conditions as damage assessments and cleanup begins. Unfortunately, numerical guidance is indicating the potential for deep tropical moisture to move into coastal areas of Texas and Louisiana by mid next week. A moisture axis in the southern Caribbean will move over the Yucatan Peninsula late this week/early weekend into the southwestern Gulf of Mexico. This may lead to the development of a surface low off of the Texas coast by early to mid next week.

This would aid in deep tropical moisture potentially being pulled into Texas as an upper-level low is situated across the Panhandle of Texas–leading to precipitation chances. At this time, it appears a surface cold front will be situated somewhere across Texas, which could enhance precipitation, too. As the low moves eastward, it will aid in precipitation chances for Louisiana.

Current moisture axis in Caribbean (GFS)

Deep moisture in southwestern Gulf of Mexico by Monday morning (GFS)

Deep moisture in southwestern Gulf of Mexico Wednesday afternoon (GFS)

Precipitation forecast through 7 days from NWS (please note: this map will change over the next few days and it looks plausible that higher precipitation amounts will shift northward)

This is still several days out, so a lot will change; however, this scenario is plausible and needs to be closely monitored. It’s to early to determine the strength of this low, but it is possible a tropical cyclone (TD or TS) could evolve. Any additional rainfall next week will quickly cause flooding. Keep checking back for updates!

Tropical Storm Watch in the Carolinas

Tropical Storm Watches have been posted from the South Santee River in South Carolina to Duck North Carolina, including the Albemarle and Pamlico Sounds.

Irma

Tropical Update

Florida has been experiencing heavy rains for the past several days at this system spun in the area.  Some areas have seen several inches of rain over the past few days as this system slowly meandered up the peninsula.  This system has been watched for a while as it slowly moved up, but interactions with land and conditions that were neutral or negative for tropical development continued to prevent this system from developing further.   Now that the system is heading over the warm water of the gulf stream, convection is beginning to increase and the storm is organizing despite its sheared environment, which Hurricane Harvey has been helping to maintain.  These storms are starting  to get some separation and we expect to see Tropical Storm Irma form in the next couple of days.

tropical

Model Analysis

Steering currents across the South of the US have been weak as of late.  This is why both this system and Harvey are moving so slowly, as you can see in the early movement of this system.   This will begin to change as a trough moves into the Central United States and begins to make this system move.

This system moves slowly north towards the border of South and North Carolina.  It will come very close to making a landfall here but much of the circulation will remain over water, which will slow any weakening.  This system will flow along the coast up towards the North Carolina Virginia border.  This system has the potential to hit the coastline hard with storm surge and high waves ahead of the storm as it strengthens.

As seen in the track above, as on this model image, the system is expected to make landfall along the North Carolina coast and impact the Outer Banks.  Beyond that, the forecast gets more difficult.  Some models have brought the system further out to sea, but the GFS is bringing the system closer to the coast of New England on some runs and this possibility will need to be monitored in future articles.

 

Rob

Harvey May Re-intensify Dumping Feet Of Additional Rainfall

More heavy rainfall and tornadoes are expected late tonight through at least Wednesday for Houston as well as the surrounding areas. This is bad news for these areas because 30″ of rain has fallen in some areas. Currently, Tropical Storm Harvey is situated over Texas but is inching closer to the coast–likely reemerging over the northern Gulf by Monday morning. Harvey has maximum sustained winds of 40 mph at this hour with a slow movement of 2 mph to the SE.

NHC Cone

The position of Harvey and slow movement place Houston and much of southern Texas and central Texas in a favorable area for very heavy rainfall for the next few days. As aforementioned, once Harvey moves back over the Gulf of Mexico by Monday morning, it is possible that Harvey will re-intensify into a strong tropical storm (possible maximum sustained winds of 60 to 65 mph). Harvey will then move northeastward, slowly, making landfall just south of Houston by Wednesday morning. This scenario would aid in heavier rainfall rates and an increased tornado threat for much of the mid-Texas coast, upper-Texas coast, southern parts of north Texas, and western Louisiana.

European (Wednesday morning)

3km NAM Rainfall Totals (through Tuesday evening)

A big concern is tonight (Sunday night) for Houston and its suburbs. Short range guidance indicates a feeder band from Harvey may situate itself over this area. These feeder bands can produce rainfall rates of 4-8″ per hour and tornadoes. This will only exacerbate the flooding issues across Houston and do so during the most dangerous time for flooding (at night). The HRRR is indicating 10-24″ may fall over the next 18 hours in the Houston area.

HRRR Future Radar (tonight)

HRRR Rainfall Totals (through 18 hours)

Once Harvey moves inland, again, into Texas on Wednesday, the path becomes uncertain. The uncertain path, and the slow meandering of Harvey over the past few days, is because there is a lack of upper-level features to act as a magnet and steer Harvey out of Texas. The steering currents are too light, and Harvey is ‘stuck’ between a mid-level high to its west and the subtropical ridge across the southeast. This may change by late week into the weekend however, however. An upper-level trough appears to dig into the central plains, which may draw Harvey northeastward. This would place parts of northeastern Texas, southern Arkansas, northern Louisiana, and western Mississippi in a favorable area to see rainfall from the remnants of Harvey. The remnants would produce flooding for these areas. By Saturday, it is possible isolated areas in southeastern Texas may see 50-60″ of rainfall.

Spaghetti Plot

European (Friday morning)

WPC Precipitation Forecast (through 7 days)

Firsthand Weather will have updates as needed!