Potential Tropical Cyclone
The National Hurricane Center (NHC) has officially classified the low in the southern Gulf of Mexico as a Potential Tropical Cyclone. This system has sustained winds of 40mph and is moving towards the north at 9mph. Tropical Storm Warnings have been issued for parts of the Louisiana coast and Tropical Storm Watches have been issued for parts of the Louisiana coast and upper-Texas coast as the system is expected to continue a north to northwesterly motion towards the Louisiana/Texas coastline.
So what is a potential tropical cyclone?
This is a new classification the NHC uses to provide more detailed guidance on systems that are not yet tropical depression or tropical storm strength, but have a high chance of becoming a tropical storm or hurricane within the next 48 hours and impact land. This new classification system allows for National Weather Service offices to issue Tropical Storm Watches/Warnings in advance.
Projected Path of Potential Tropical Cyclone
Wind speed Probability Map
Large impacts will be felt from the Florida Panhandle to the upper-Texas coast from tonight through Thursday. The biggest threat is heavy rainfall in these areas where coastal areas will see 6-12″ with locally much higher amounts (potentially isolated 12-20″ near the Louisiana and Mississippi coasts). Areas further inland across the Gulf states (Florida, parts of Georgia, Alabama, Mississippi, Louisiana, and parts of Texas) will see heavy rainfall, too. The metro areas of Houston and New Orleans will have an enhanced flash flooding threat due to the impervious surfaces throughout the metro. This is not a hype forecast or to create panic, but catastrophic flooding could be observed due to rainfall in coastal areas.
Potential rainfall map through this week (NCEP)
The cyclonic flow around the low will also allow for sea water to ‘pileup’ causing flooding for areas just above sea-level for Louisiana and Texas. Secondary threats are wind (depending on the strength of the system) and isolated tornadoes. The latest guidance is indicating this system may become a strong tropical storm–borderline hurricane. This will be addressed in a future article, as well as the impacts as this storm moves inland. Keep checking back for updates!
12km NAM near-surface winds (Tuesday afternoon)
12km NAM predicted radar (Tuesday afternoon)
12km NAM near-surface winds (Wednesday evening)
12km NAM predicted radar (Wednesday evening