Dorian Nearing Major Hurricane Strength

As of 11am, Hurricane Dorian is now currently just one mph shy of attaining major hurricane strength and will continue to strengthen throughout today and this weekend. Previously, an upper-level low pressure system has produced some shear on Dorian’s west side, but as shown by the water vapor imagery loop, the upper-level low is making its way westward. It’ll continue westward and pass between Cuba and the Florida Keys, while Dorian takes advantage of high sea surface temperatures and lower shear off the Southeast U.S. coast. Although there may be later opportunities for Dorian to encounter shear, there won’t be much of an issue for the storm in the foreseeable future.

Both the European and GFS operational guidance insists on a Florida landfall. The GFS is a bit farther west than the European model, but both models agree that there will be an eventual turn northward that’ll take the storm through Florida, Georgia, and the Carolinas. We will have to continue to monitor the strength of the Bermuda ridge, which still could allow for a turn northward more quickly. However, we often struggle when attempting to nail down when a tropical system will turn. It can remain a challenge until the turn actually occurs; thus, we have no choice but to warn those who could suffer major impacts.

The latest forecast loop from the European model has Dorian making landfall in Florida and then proceeding to ride up along the Southeast coast, which is a completely viable solution. When we look at the European ensembles, we can see that some of its members take Dorian northward before hitting Florida and then have it impacting the Carolinas, which is another viable solution. So again, we’re currently faced with two potential scenarios, both of which could produce devastating impacts for certain regions. Luckily, we’re able to narrow down the region that will face potential impacts, but specifics are still iffy, as always.
Dorian projected path

As I’ve mentioned in several updates, please take into account the flooding risk with Dorian. The Weather Prediction Center has produced a 7-day rainfall forecast for this storm. Depending on track, rainfall totals could be higher, even into the Carolina. Around 1-2 feet of rainfall would not be out of the question, since Dorian should slow and could ride inland along the Southeast coast.

Dorian rain forecast

The National Hurricane Center has maximum sustained winds reaching 140 mph with higher gusts. This seems perfectly realistic, given favorable environmental conditions. Their current track has Dorian hitting south-central Florida as a major hurricane and then turning northward. Although you should expect changes to this forecast in the coming days, you should plan as if this forecast will come to fruition.

Hurricane Dorian forecast track

We will continue to monitor this situation closely and will provide you with new updates as the forecast changes.

Hurricane Dorian Likely To Strengthen On Its Path Towards Florida

Hurricane Dorian continues on a northwestward trajectory as it moves away from Puerto Rico. Dorian has begun to encounter a considerably moister environment; thus, dry air entrainment into the storm’s circulation will become less of a problem with time. As of the 5pm ET advisory, Hurricane Dorian remains at category 1 status, but a steady or even rapid change in strength should occur over the next 24 hours. An upper-level low pressure system to Dorian’s west-northwest will impinge some southeasterly shear on Dorian’s left side, but as the upper low continues on a westward path, wind shear will lessen in Dorian’s vicinity within the next 24 hours. Sea surface temperatures are well-above the necessary 26.5°C threshold to support tropical development and intensification. With everything considered, we feel confident that Dorian will remain in an environment that will allow continued strengthening. Of course, there’s always the possibility that some additional shear or dry air could become an issue in a few days, but there’s nothing currently that we see as being an issue for the storm.

Right now, we need to figure out where Dorian will go. Looking at climatology, the majority of tropical systems that have previously been within the vicinity of Dorian’s location eventually approached Florida but actually made landfall in the Carolinas. A handful of the storms did go into the Gulf of Mexico, and only a few made landfall in Florida. Although climatology can be extremely useful, one does have to be careful when trying to use it to predict future events. Each storm is different.

Similar paths to Hurricane Dorian

With that said, I suspect that the more eastward trend in the model guidance is closer to what will occur, but the current scenario could be worst from both a flooding and wind damage perspective. The strength of the Bermuda ridge will remain crucial as to just how far west Dorian makes it before making a northward turn. This actually brings back flashbacks of Hurricane Matthew, because we really struggled to pin down when that turn would occur. Matthew luckily turned before significantly impacting Florida, but as most remember, the storm eventually produced copious amounts of rainfall in parts of the Carolinas.

Dorian flooding rainfall forecast

The latest GFS and European model currently project Dorian to make landfall in south-central Florida as a powerful hurricane before riding up the Florida coastline and then moving into the Carolinas. At this point, I can’t entirely discount that scenario. Broad troughing should remain in place across the northeastern U.S. This means that the primary flow down through the Ohio Valley and Mid-Atlantic will remain from the northwest. Embedded shortwave features moving within the flow and broad troughing could keep the Bermuda ridge weaker than what has previously been shown by the models. Plus, if Dorian were to move more slowly than currently anticipated, this would allow more time for troughing to weaken the Bermuda ridge. This needs to happen for the northward turn to occur more quickly. We can hope that a quicker turn to the north will prevent a Florida landfall, but uncertainty remains too high to say with confidence that this scenario will occur. Personally, if I were along the Florida east coast, I’d be planning for a major impact. For those in the Carolinas and eastern Georgia, flooding could become an issue, and at this point, I can’t discount a northern South Carolina and North Carolina landfall.

Hurricane Dorian projected path

Right now, the likelihood of Hurricane Dorian entering the Gulf of Mexico has decreased quite a bit. Florida should continue to prepare for a potentially catastrophic and life-threatening event, and we will continue to make you aware of any changes in the forecast.

Taste Of Fall–Plus, Tropical Troubles Off The Southeast Coast?

If you’re tired of the heat and ready for a taste of fall, you’re in luck. Numerical guidance has been fairly consistent in suggesting a pattern change that will lead to a nice cool down for much of the central and eastern United States for the end of August into the first week of September.

Numerical guidance is suggesting an amplified trough will dig into the central U.S. & begin to deepen next week as it moves east. This will act to send a strong cold front south into the Southern Plains by late next week, followed by a slow push into the South & Southeast by late next weekend into the following week.

The Climate Prediction Center concurs and suggests days 8-14 (August 29th through September 4th) have a high probability to see below average temperatures for much of the central & eastern United States (see Fig. 1). It should be noted, there are some significant disagreements on the fine details of the setup, but overall, all guidance is suggesting a cool down will occur.

Fig. 1: CPC Temperature Outlook Days 8-14

What will the temperatures look like for the South & Southeast? It appears highs will fall into the low to mid-80s with overnight lows in the upper 50s & 60s. But hey, that’s way better than 90s & 100s! Here is a look at the temperature trends for several cities in the South & Southeast through 16 days (please note these values are likely to change significantly over the next several days–it is possible the highs/lows will decrease further towards the beginning of September):

Fig 2: Atlanta, GA Temps
Fig 3: Birmingham, AL Temps
Fig. 4: Columbia, SC Temps
Fig. 5: Jackson, MS Temps
Fig. 6: Nashville, TN Temps
Fig. 7: Shreveport, LA Temps
Fig. 8: Dallas, TX Temps
Fig. 9: Oklahoma City, OK Temps
Fig. 10: Litte Rock, AR Temps

Firsthand Weather is also keeping an eye on a tropical disturbance over the Bahamas. This disturbance has become better organized over the past 24 hours thanks to the low wind shear (see Fig. 11). A northwest movement toward the east coast of Florida is likely over the next 24-48 hours, followed by a northerly then northeasterly movement just off of the Southeast Coast through the weekend into early next week.

Fig. 11: University of Wisconsin Wind Shear Map

The disturbance will move into continued favorable environmental conditions which may allow for a tropical cyclone (tropical depression or tropical storm) to develop over the weekend. The National Hurricane Center has upped the chances for development to 30% over the next five days (see Fig. 12). The EPS is on board with development into a tropical depression over the next 24-72 hours with probabilities greater than 70% (see Fig. 13).

Fig. 12: NHC Five Day Tropical Weather Outlook
Fig. 13: EPS Tropical Depression Probability

Numerical guidance indicates this system will stay just off of the Southeast Coast (Georgia, South Carolina & North Carolina) from early week into mid-week as the system moves northeast. Increased rain & rough seas are likely for Florida over the weekend and possible enhanced moisture and rough seas for coastal areas of the Carolinas early week through mid-week. If this system develops into a tropical cyclone, it will be named Dorian. Please note, there is still some uncertainty with the evolution and track of this system so keep checking back for updates.