Tropical Depression 8 & 9: Both with Potential US Impacts
There are two brand new tropical depressions that the US needs to keep a close eye on. Tropical Depression Eight is located over the eastern Atlantic, while Tropical Depression Nine is located over the Florida Straits. Each could have possible impacts on the US in the coming week. Let’s examine.
First, lets examine TD 8. The current information as of the 5pm EDT advisory is as follows. TD 8 is currently located at 31.8N 70.9W with maximum sustained winds of 35mph. It is moving to the west at 9 mph.
Here is the latest forecast discussion from the National Hurricane Center:
The low-level center of the depression is now exposed, with the deep convection diminishing and displaced to the northwest of the center due to about 15 to 20 kt of southeasterly shear. Data from an Air Force Reserve Hurricane Hunter aircraft suggest that the intensity remains 30 kt based on the highest believable SFMR winds and peak flight-level winds of 32 kt. Given the current satellite presentation and an environment that is only expected to be marginally conducive for intensification, only modest strengthening is shown in the official forecast, with the depression expected to become a tropical storm in the next day or two. After that time the shear should increase as the system accelerates northeastward, and the global models show the cyclone being absorbed by a front in about 4 days. The NHC intensity forecast is close to the intensity consensus through 48 hours and a little below it at 72 hours. The initial motion estimate is 280/08. While the synoptic reasoning has not changed, the sheared state of the cyclone could lead to some erratic motion if it remains a shallow system. Assuming deep convection returns, the cyclone is expected to gradually recurve during the next 48 to 72 hours, with a slow northwestward motion expected in 24 to 48 hours, bringing the center just offshore of the Outer Banks of North Carolina. Given the uncertainty in the intensity forecast and the timing of the approach to the coast, a tropical storm watch is not being issued at this time, but one may be required later tonight.
Given this information the east Coast from the coastal carolinas up to Long Island, NY need to closely watch this system. Even if it is only a tropical storm it could have significant impacts for coastal regions from flooding to beach erosion. Here is the official forecast track for TD 8:
Next, let’s examine TD 9 in the Florida Straits.
The current information as of the 5pm EDT advisory is as follows. TD Nine is currently located at 23.7N 81.7W and has 35 mph sustained winds. It is moving west at 9 mph.
Here is the latest forecast discussion from the National Hurricane Center:
Data from a NOAA Hurricane Hunter aircraft indicate that the area of low pressure located in the Florida Straits now has a well-defined center. Satellite imagery shows a significant increase in the convective organization today, and as a result the system is now classified as a tropical cyclone. The initial intensity is set to 30 kt based on the highest believable wind data from the aircraft, which reported a central pressure of 1009 mb. The depression will be moving through a marginal environment for intensification during the next day or so, with vertical shear of 15 to 20 kt. As a result only slow strengthening is expected in the short term. Later on, the environment may improve a little as the shear is forecast to decrease somewhat and become southwesterly, which should allow for a little more strengthening. However, there are mixed signals in the model guidance, with the ECMWF now showing the cyclone dissipating in the Gulf, while the GFS delays development until 4-5 days. Much of the tropical cyclone guidance is more aggressive. Given this uncertainty, the NHC intensity forecast is quite conservative and shows the system peaking at 45 kt, below all the explicit intensity guidance in consideration of the negative signal from the ECMWF. Needless to say, the confidence in the intensity forecast is even lower than usual for this system. The initial motion estimate is an uncertain 270/09 given the recent formation of the center. The cyclone will be steered in the short range by a mid-level ridge centered over the southeastern United States. This ridge will weaken in 2-3 days, which will cause the cyclone to slow down and turn northward during this time. Late in the period a northeastward acceleration is expected ahead of an approaching mid-latitude trough. There is reasonable agreement in the track of the cyclone in the global model guidance, although there is a fair bit of along-track spread late in the period. The NHC forecast is close to a consensus of the GFS and ECMWF through day 4 and is a little faster than the GFS and GEFS ensemble mean at day 5.
Forecasting this particular tropical system is more uncertain than TD 8 because of the environment is is located in. However even if it were never to form into a tropical storm the tropical moisture alone could create major problems for the Gulf Coast region. You may remember the significant flooding in Louisiana from just a couple weeks ago. That was a result of “tropical moisture”. Let’s take a look at the current official forecast track for TD 9 from the NHC.
Notice how wide the cone of uncertainty is first of all. We could possibly have a tropical system of some sort off the southeast coast of Louisiana to the west coast of Florida. Or it may just still be wandering in the Gulf of Mexico in 3 days. As of right now I would urge the ENTIRE Gulf coast region to pay special attention to this tropical system. Now is the time to make sure you have your tropical disaster plan in place. Don’t wait till the day before. Having lived in Miami, FL for nearly 8 years and surviving numerous Tropical storms and hurricanes from 2002-2009 you do not want to be caught off guard. Stay with Extreme Weather Videos for the latest tropical developments!
