The ingredients that usually trigger activity begin to fall into place: very warm waters in the tropical Atlantic and the Caribbean, signs of downward wind shear in high layers and a phase of the Madden-Julian Oscillation more favorable for the growth of deep cloud cover. If this pattern consolidates, The next few weeks could be much busier..
Season status and systems formed
So far they have appeared Andrea, Barry and Chantal, three short-lived named storms, conditioned by dry air, Saharan dust and hostile winds at altitude. Dexter It is the fourth on the list and is moving over open sea; the forecast points to a transition to extratropical cyclone no coastal warnings in effect.
The count would be in line with what is usual for mid-August, but the accumulated energy remains contained: the index ACE at the beginning of July it was around 1,5 units, below the average for that date. Still, a quiet start doesn't determine the final result: historic seasons They started slowly and took off at the seasonal peak.
Factors that have limited and now favor development
During June and July he dominated a high vertical shear which disorganized the tropical waves, in addition to recurrent episodes of Saharan dust and sectors with dry air which subtracted moisture from the convection. A pattern of high pressure In the Atlantic, it also diverted systems towards less favorable trajectories.
That script is starting to change. Trust models point to a weakening of winds at altitude in sections of the Main Development Region, while the MJO transitions into phases that typically drive tropical convective weather. This shift improves the environment for African waves get organized.
The sea contributes excess fuel: the classic threshold of 26,5 ° C It is widely exceeded from the African coast to the Caribbean and the Gulf of Mexico, where values around have been observed 32 °C near FloridaIn the MDR, which started the summer less warm than in recent years, the temperatures have risen, increasing the potential for intensification if the rest of the ingredients accompany it.
Updated forecasts and probabilities
La NOAA maintains an expectation of activity above normal and has adjusted its seasonal forecast to 13-18 named storms, of which 5-9 could be hurricanes and 2-5 reach a higher category. The agency estimates a 50% chance active season, a 35% close to normal and a 15% under.
La Colorado State University also projects an animated season: 16 named systems, 8 hurricanes y 3 of great intensity. Their models are situated in the 52% the probability of a major hurricane making landfall in the Caribbean Sea, in the 48% for the continental US coast, with estimates of 24% for the east and south coast 31% for the Gulf Coast. The driving force behind these figures: warmer waters than usual and an equatorial Pacific in neutral phase.
What is being monitored right now
The NHC monitors a tropical wave in the central Atlantic which could be organized in the next few days; the probability of development in the next week has been estimated at around 60% while moving northwest through open waters.
Another focus of attention is a low pressure zone versus southeastern US, with a low probability of evolution and a forecast trajectory far from the coast, losing favorable conditions later on.
In parallel, Dexter continues out to sea without direct threat to land and will tend to transition to extratropical in the short term, something that frequently occurs when systems ascend to higher latitudes.
