Dorian was never really dead, but it was certainly on life support for about 48 hours over the weekend. And while its vital signs seemed to be improving Sunday night, the road back to a healthy tropical storm is an uphill climb over the next two days. Conditions for redevelopment as a tropical cyclone are only marginally favorable, and the forecast environment near the system’s expected track isn’t much better either. The National Hurricane Center now says Invest 91 (Dorian’s remnants) have only about 30 percent chance of being classified as a tropical depression or storm within the next 48 hours.
- Thunderstorm activity wained a bit Monday and no center of circulation was found by the Hurricane Hunters
- Dry air to the south and wind shear approaching from the west likely to prevent tropical redevelopment through Tuesday
- Will move through Bahamas Wednesday, possible influences on south Florida Thursday or Friday as a tropical wave or weak tropical storm
UPDATE MONDAY AFTERNOON: An Air Force reserve unit reconnaissance aircraft flew into the system Monday afternoon and found no center of circulation or closed area of low pressure. Surface pressures were quite high and wind speeds generally under 35 mph, data that confirms Invest 91 is nothing more than a tropical wave at the time. The system sits approximately 200 miles north of the Puerto Rico and is moving west-northwest at 15 mph. Thunderstorms are weak and disorganized near and north of the system’s perceived center.
PAST 24 HOURS: A significant amount of convection (or thunderstorms) developed about 100 miles to the northeast of what was perceived as the area of interest late Sunday evening. Satellite data also suggested that the system had become healthier aloft, with a large area of outflow depicted in the cirrus clouds above the thunderstorms. This is usually a sign that high pressure is building above the system and allowing it to breathe, or giving it an exhaust pipe if you will. The aforementioned convection continued to fire overnight, but in a rather disorganized way, so as of Monday morning Invest 91 was still just an open tropical wave.
FORECAST: The remnants of Dorian have at least three more days over warm ocean water and must be watched closely, but there are two major roadblocks to keeping it from redeveloping into a tropical cyclone in the near future. Water Vapor imagery showed a large area of dry air sitting to the south of Invest 91 that was likely to start influencing the thunderstorm activity again in the next 24 hours. Dry air often suppresses the robust thunderstorm development needed for a tropical cyclone to mature. The second hurdle to development is a large area of low pressure aloft, sitting just to the west (or in front of) Invest 91. Stronger winds aloft out of the southwest is already starting to create an increase in wind shear, which will also work against Invest 91’s chances for redevelopment in the coming days.
As is typically the case of a weak system, model data is in respectable agreement on Invest 91’s forecast path but almost clueless on the projected intensity. The general consensus of the most-reliable forecast models is for the remnants of Dorian to continue moving in a west-northwest fashion toward the Turks and Caicos Islands Tuesday, nearing the Bahamas on Wednesday. The path thereafter is largely dependent on the strength and structure of the system, which is highly unknown at this point. At this point, it would be safe to say that some influences – such as heavy rain showers and gusty winds – from Invest 91 (or the remnants of Dorian) could be felt in parts of South Florida as early as Thursday. There is only a low chance that there would be impacts on Florida’s Atlantic Coast from a weak tropical system Friday or Saturday.
Considering the significant level of uncertainty surrounding Invest 91, Floridians should stay aware and informed of future forecast updates throughout the week. WRUF Weather keeps you updated on the tropics every hour at 20 past on WRUF-TV, online constantly, and on Twitter with urgent updates @WRUFWeather.