A new named storm will likely form in the Caribbean soon
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It looks like the United States and the Gulf of Mexico are safe from anything that might come from this disruption, but the risk is increasing for places like Nicaragua, Honduras and Belize.
After a quiet start to the hurricane season, a surge in activity has brought this year’s activity closer to average. Fiona and Ian have contributed the most to closing the storm deficit, and the Atlantic basin is now only 20% behind the average in terms of ACE, or Accumulated Cyclone Energy. It is a measure of how much energy storms harvest from warm ocean waters and expend on strong winds.
In addition to the incipient storm near the Lesser Antilles, there is also a tropical depression just under 500 miles west of the Cape Verde Islands, but it is not expected to strengthen. or given a name.
Potential development of the Caribbean system
By mid-morning Wednesday, the system over the Windward Islands was bringing heavy rain there and into northern Venezuela. Trinidad and Tobago was also drenched, with heavy shower and thunderstorm activity from the tropical wave.
There were a few limiting factors to the storm. It lacks a “closed circulation”. This means that the winds turn, but they do not make a complete circle. This weakens the structure of the storm and prevents it from developing easily.
This can be seen in scatterometer data – or measurements from a satellite-based instrument that determines wind speed and direction through the movement of clouds and ocean waves. We can see that there is an obvious curvature, but there is no westerly wind “winding up”. Until that happens, the system will not be declared a tropical depression.
Instead, what is visible is an axis of vorticity, or spin. If part of this rotation along the windshift 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.
For now, the system is working against strong wind shear, or a disruptive change of wind and/or direction with altitude, to its north. This contributes to destabilizing the storm and hampering its organization. Wind shear is less to the south, which is why the storm may veer south and scrape along the South American coast.
In the days to come, it will probably escape this shear as it approaches the ABC islands (Aruba, Bonaire and Curaçao) while gradually consolidating.
The National Hurricane Center estimates the disruption has an 80% chance of developing eventually. Weather models indicate that the system will likely become a tropical storm by the end of the week as it passes through shear.
Despite Ian’s recent passage, sea surface temperatures in the Caribbean are still very warm and will be ripe for intensification. What is different this time, however, is that the air pattern aloft will not be as conducive to rapid intensification.
With Ian, a clockwise rotating high-pressure system at upper levels was present aloft to aid in the “exit” or escape of the storm; the more air that exits a storm from above, the more warm, moist air that can enter to fuel the storm. This time, the high appears to be moving north-northwest.
Still, the new system could eventually attempt to become a hurricane, with Julia being the next name on the list. Either way, he should reach Nicaragua by Sunday to Monday. Rainfall totals of 12 to 24 inches are possible, especially on higher ground where landslides and flooding can be expected.
High pressures at medium levels should keep the system far enough south that it cannot turn north towards the Gulf of Mexico or Lower 48.