Sep 26: Increasing Confidence in Direct US Impacts from PTC 9 (Formerly 94L)

While there are still some question marks in the exact path and intensity of future Imelda, it has become more likely that the Southeast coast of the US will get direct impacts from the system. First of all, take a look at the system below. It has been slowly organizing near Cuba throughout the day on Friday:

The NHC designated 94L as Potential Tropical Cyclone (PTC) 9 at the 5 pm advisory on Friday.  As a reminder, a PTC is issued when a tropical depression or storm hasn't developed yet but tropical-storm conditions are expected within 48 hours and watches and/or warnings need to be issued. Last year, Helene was a PTC before becoming Helene. That is the case here because the storm is forecasted to move through the Bahamas this weekend. The initial forecast for PTC 9: 

From the Bahamas, the system will continue to move generally to the north, between the upper low over the southeast and the Bermuda high and by Monday morning should be off of the southeast coast. A faster system would be more influenced by the upper level low over the Southeastern US and would move inland. A slower system would be more influenced by Humberto and could stall right at the coast. A simple schematic is below:

The exact path and intensity of the system is still a difficult forecast but models have honed in on at least a strong tropical storm if not hurricane making landfall somewhere late Monday into Tuesday along the southeast coast, likely South Carolina:

At this point, it doesn't appear like PTC9 will develop into a major hurricane but intensity forecasts are especially difficult. It should also be mentioned that Hurricane Humberto rapidly strengthened into the 3rd major hurricane of the season on Friday so we have had 3 hurricanes and all 3 have become major. Let's hope Imelda doesn't follow that same pattern. As of now, it looks like 60-70 mph winds will be what Imelda brings:

While the potential wind impacts shouldn't be ignored from Imelda, the biggest calling card from this system will likely be heavy rains that could lead to major flooding across the Carolinas. This potential flooding will be aided by a Predecessor rain event (PRE) this weekend, far in advance of Imelda. It's unfortunate that a year ago today, Helene was causing catastrophic flooding across the Southern Appalachians due also to a PRE. You can see the moist tropical air moving north ahead of the system starting this weekend:

Initial rain total forecasts below could go up depending on if Imelda stalls or moves quickly inland. Right now, generally 3-5" of rain are being forecasted for much of the Carolinas with 5-8" right along the coast. These numbers could easily double if the system stalls over the region:

The key messages you should take from this forecast are below:

1. PTC9 will likely become a tropical storm this weekend over the Bahamas, bring strong gusty winds, heavy rainfall, and elevated surf conditions. 
2. The threat of heavy rainfall from coastal GA through the Carolinas continues to increase daily. Remember that fresh water flooding is one of the leading causes of death in tropical systems. This was tragically witnessed just last year with Helene.
3. PTC9 will likely be a hurricane as it approached the Southeast coast early next week. Regardless of landfall, coastal residents should monitor the forecast and stay prepared as there are over 2 months remaining in the hurricane season.