City of Central

Southeast Louisiana and Southern Mississippi partners - 

Here is an update concerning Potential Tropical Cyclone Eighteen in the central Caribbean Sea.

Unrelated to that storm, we have also included information regarding the coastal flood threat during high tide this morning and again Monday night.

Changes from previous update: 

·  The threat of impacts to the local area has remained roughly the same, with high uncertainty in the forecast beyond midweek.

Tropical Overview:

·  There is a very high (near 100% chance) that Potential Tropical Cyclone Eighteen will develop into a tropical depression or tropical storm later today or tonight. The next name on the naming list is Rafael.

·  It is forecast to move generally northwestward and strengthen into a hurricane as it approaches western Cuba.

·  It is then forecast to move into the southeastern Gulf of Mexico where it should begin to gradually weaken as it encounters higher wind shear and drier air on a continued northwest trajectory.

Confidence: 

It should be noted there is higher than normal uncertainty in the forecast, especially beyond midweek. The eventual track and intensity of this system will depend greatly on the strength of a high pressure system over the western Atlantic and Florida, the timing of a low pressure system forecast to move into the plains states during the middle to latter part of the work week, and how the storm interacts with Cuba.

Confidence in storm track and intensity in the Gulf of Mexico should increase during the next day or so as the system becomes better defined and more aircraft reconnaissance planes sample the storm.

Tropical Impacts:

·  Given the high uncertainty in the forecast beyond midweek, it is too soon to say exactly what impacts this system could bring to the local area.

·  *IF* this storm continues to move toward the local area, any impacts would most likely occur during the Friday/Saturday time frame.

·  Probability of tropical storm-force winds has increased slightly since yesterday across land points through midday Friday though the messaging remains unchanged. These probabilities are likely to change as the forecast is refined over the coming days.

The graphics below highlight the current track forecast for Potential Tropical Cyclone Eighteen as well as the probability of sustained tropical storm winds through midday Friday.

Coastal Flooding Overview:

·  Unrelated to Potential Tropical Cyclone Eighteen, there is minor coastal flooding ongoing during high tide this morning and is expected again on Monday night.  

·  Persistent and strengthening east and southeasterly winds over the Gulf waters has resulted in tides rising above normal.

·  Minor flooding is occurring and a coastal flood advisory is in effect for all coastal areas. Waters will recede during the low tide cycle today before rising again tonight.

·  There is a low (10%) chance of up to 2.5 feet of inundation along some east and southeast facing shores Monday night and a coastal flood watch has been issued for these areas.

·  High tide is generally forecast to occur between 11pm and 5am along the open coast, with delayed arrival farther inland along bays, rivers, bayous, etc.

Coastal Flooding Impacts:

·  Minor flooding of low lying roads, lots, and parks is likely around the time of high tide tonight in the advisory area.

·  Moderate flooding with inundation of low lying parks, lots, and ground-level storage, and some road closures are possible around the time of Monday night in the watch area.

The graphic below highlights the coastal flood advisory and watch areas.