A new storm is developing in the southeastern Caribbean, a week after Hurricane Ian made a devastating Category 4 landfall in southwest Florida.
Weather models have been struggling to predict the emerging disturbance that hung over the Windward Islands on Wednesday morning. However, it is on the verge of becoming a tropical depression, which would pave the way for it to mature into a named storm or hurricane.
Cone of Confusion: Why some say the iconic hurricane map misled Floridians
It looks like the United States and the Gulf of Mexico are safe from anything that might develop from this disruption, but the risk is mounting for places like Nicaragua, Honduras and Belize.
After a quiet start to hurricane season, a surge in activity has brought this year’s activity closer to average. Fiona and Ian have done the most to make up the storm deficit, and the Atlantic Basin is now just 20 percent behind the mean in terms of ACE, or Accumulated Cyclone Energy. That’s a measure of how much energy storms harvest from warm ocean water and expend on strong winds.
In addition to the young storm near the Lesser Antilles, there is also a tropical depression a little less than 500 miles west of the Cape Verde Islands, but it is not expected to strengthen or be given a name.
Development of a potential Caribbean system
From Wednesday morning, the system brought heavy rain over the Windward Islands there and in northern Venezuela. Trinidad and Tobago was also drenched, with heavy showers and thunderstorms driven by the tropical wave.
There were a few limiting factors for the storm. There is no “closed circuit”. This means that winds rotate but do not form a complete circle. This weakens the storm’s structure and prevents it from developing easily.
You can see that in scatterometer data — or measurements from a satellite-based instrument that uses the movement of clouds and ocean waves to determine wind speed and direction. We can see that there is an obvious curvature, but there is no westerly “wrap” of the wind. Until then, the system will not be declared a tropical depression.
What is visible instead is a vorticity or spin axis. If part of this rotation along the wind-shift line east of Trinidad and Tobago is stretched vertically by a thunderstorm, it could become the de facto center. Then the storm would organize around this rotational column and likely become a tropical storm.
The system is currently working against strong wind shear or a disturbing wind and/or direction change with altitude to the north. This is a conspiracy to unbalance the storm and hamper its organization. Wind shear is lower in the south, which is why The storm may turn south and scrape along the South American coast.
It is likely to escape this shear in the coming days as it approaches the ABC Islands (Aruba, Bonaire, and Curaçao) and gradually consolidates.
The National Hurricane Center estimates the disruption has an 80 percent chance of developing. Weather models suggest the system is likely to become a tropical storm by the end of the week as it overcomes shear.
Despite Ian’s recent passage, sea surface temperatures in the Caribbean are still very warm and will be conducive to intensification. What’s different this time, though, is that the upper air pattern won’t be quite as conducive to rapid intensification.
At Ian, a clockwise rotating high-pressure system was in place on the upper levels to aid in the ‘drain’ or exhaust of the storm. The more air that exits a storm from above, the more warm, moist air can enter to fuel the storm. This time the high pressure area appears to be shifting to the north-northwest.
Still, the new system could eventually attempt to become a hurricane, with Julia being the next name on the list. Whatever comes of it should reach Nicaragua by Sunday through Monday. Rainfall totals of 12 to 24 inches are possible, particularly in the higher terrain where mudslides and flooding can be expected.
High pressure at mid-elevations should push the system far enough south that it cannot turn north toward the Gulf of Mexico or the Lower 48.