As we wait for the 5p ET advisory cycle on TD 1 to come out, we're looking at a very disorganized system sitting somewhere in the SE Gulf of Mexico or NW Caribbean. While wind shear, per the satellite analyses from the Univ. of Wisconsin, is fairly low over the system, it has become more disorganized today as multiple low-level circulation swirls rotate about a mean gyre centered somewhere near the Yucatan Channel. Pressures still remain fairly low -- 1003-1005mb -- and winds are decent within the convection (25-30kt), but there's little organization to the depression at this time.
It's not that unexpected to see systems in their initial stages of development go through fits and spurts before consolidating and beginning to strengthen. It's interesting -- I remarked to a colleague today that the features that tend to negatively impact tropical cyclones -- like upper level lows -- seem to be necessary to even see some tropical cyclones in the first place. Case in point, TD 1: were it not for the development of an upper-low just to its west, the environment would not have become nearly as diffluent at upper levels, convective development would have been suppressed, and the feature in the EPac may have been that which developed. Instead, the upper low formed, creating a diffluent environment over the storm and sending moisture northward -- preconditioning the Gulf with moisture to replace the dry air that was (and still is) prevalent -- allowing the system to become "organized" in the NW Caribbean. Yet, it'll be this feature plus the trough to the NE that keep this thing sheared. TD 1 certainly is going through those fits and spurts right now. I expect it to ultimately become better organized, but it may not be until the diurnal convective maximum sets in overnight before it begins to do so. I expect a better defined center to develop just southeast of where the center of the feature is now, somewhere between the Isle of Youth and Cancun/Cozumel, and it should have a period of time over the next 24 hours or so to do so in an environment of relatively light shear.
So, where is it going to go from here? The subtropical ridge over the Caribbean and the upper low over the southwest Gulf of Mexico should provide the impetus for TD 1 to generally move northward over the next day or so. I don't think it will move all that much or all that fast initially, given that it will likely spend some time organizing in the NW Caribbean over the course of the rest of the day. A more pronounced motion northward (or maybe north-northwestward) should commence into tomorrow. Once it gets into the north-central Gulf, model projections show the blocking pattern over the eastern & central Atlantic breaking down, with a narrow trough of low pressure rotating around the western side of the upper low currently near New England and the Canadian Maritimes. This trough should provide the impetus to kick this upper low out to sea as well as start to turn TD 1 toward the northeast.
How sharp or fast of a turn this is has yet to be determined. Models disagree on the amplitude of this trough and thus on its impact upon the storm, resulting in some disagreement in how fast and how much TD 1 turns. Some models (NAM, ) take the storm toward Louisiana at a fairly slow clip, while others (GFS and prime amongst them) accelerate the storm to the north and northeast with landfall early Monday along the southern Big Bend of Florida. Other than the outliers in Louisiana, however, most models agree on a track somewhere between Panama City, FL and Clearwater, FL, with landfall at some point on Monday.
This is in line with the official forecast and is similar to my thinking as well. Given the proclivity for these developing storms under relatively weak steering currents to track slower than predicted, I am siding moreso with the models that are a tad slower and further north along the coast line. Once the system begins to move northward, the upper low to its west will help build the subtropical ridge just a tad further northward as well, likely keeping the storm from turning too sharply. Note that the trough projected to capture the storm in the models does not even appear in the analyses at this point; thus, it is hard to nitpick what you can't even see in the model. Nevertheless, I think the eastward turn will happen, just a bit slower than projected.
As a result, I feel that those from Panama City to Tampa, with emphasis from Port St. Joe, FL to the Weeki Watchee, FL area, should pay close attention to this storm. It is a pretty safe bet to say that on such a projected track, areas along and south of the I-4 corridor should see some much needed rainfall from the depression (no matter what state of development it might end up in). I am targeting the Apalachicola to Steinhatchee area as that most likely for landfall, but extending the window of impacts much further east than west given the lopsided nature (current and forecast) of the depression. Areas west of the landfall location may see little winds and little or no rain from the depression over the next few days.
Intensity still remains a question mark given the current state of organization. It is a pretty bet to say that the depression is not currently any stronger than analyzed earlier. I feel that while not out of the question, it is unlikely that we will see TD 1 become TS Alberto today. Tomorrow, I do feel we will have a tropical storm on our hands, with tropical storm watches going up for Florida at some point during the day -- and warnings late at night and into Monday morning. Shear will increase over the storm as it heads further north, but it should be riding along the edge of the Loop current over the next day to day and a half before entering the cooler shelf waters near-shore.
A development cycle like that of TS Bonnie (2004) is most likely, with some intensification to moderate/strong TS status possible as it nears the north-central Gulf followed by weakening as it nears shore. If the storm accelerates faster toward the northeast than is projected, storm-relative shear may decrease and allow the system to maintain more of its intensity; it'll also help force the storm to become faster. Nevertheless, I do not expect a hurricane out of this depression -- and if it does reach hurricane intensity, it will likely be of minimal hurricane strength. The Loop current is always a complicating factor, but the external environment is likely too dry and features too much shear to allow the storm to explosively deepen as it heads north.
Further updates as events warrant...
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