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A widespread low-pressure system known as the Mesoamerican Gyre is developing over Central America and will bring heavy rain to much of Central America and southern Mexico next week. The Central American Gyre could bring more than 12 inches (305 mm) of rain in seven days to the Pacific coasts of Mexico, Guatemala, El Salvador, Honduras and Nicaragua, triggering flash floods and landslides that could threaten lives (Photos) 1).
A gyre is a type of monsoon depression, a weak but broad area of surface low pressure that can persist for two weeks or more over Central America and adjacent areas of the Atlantic and Pacific Oceans, including the western Caribbean and southwestern Gulf of Mexico. They are most common in May, June, September, October and November. Gyres often release smaller circulations that can develop into fully developed tropical cyclones. One of these cells formed in the Gulf of Mexico in June and became the first named storm of the season, Alberto.
The Central American gyre usually takes many days to form, and once fully formed, it takes several more days to produce a tropical cyclone. Where the Central American Gyre tropical cyclone will form is difficult to predict two days in advance, but our leading forecast models have been predicting that it will spawn the next Atlantic storm called Helen at some point.
Over the next few days, models are unlikely to focus on the likely location and timing of possible Tropical Storm Helen formation. The European model and its ensemble members favor weaker, slower-developing storms over the southwestern Gulf of Mexico; the GFS model and its ensemble members favor stronger storms farther east in the central Gulf. Since Thursday's run, both forecast groups are trending toward slower development and further westward.
In the Tropical Weather Outlook issued at 8 a.m. ET Friday, the National Hurricane Center projected a 0 percent chance of a tropical cyclone in the western Caribbean or southern Gulf of Mexico within two days and 40 percent within seven days. As of Friday, no Hurricane Hunter missions had been scheduled for the system. Due to record or near-record ocean temperatures in the Gulf of Mexico and increased ocean heat content, the potential for storms in the Gulf of Mexico is high and Gulf Coast residents should anticipate the possibility of hurricane formation in the Gulf of Mexico. Last week in the bay.
Two systems that open the Atlantic are unlikely to develop
Two disturbances in the remote subtropical Atlantic pose little, if any, threat to land areas in the foreseeable future. In the Tropical Weather Outlook issued at 8 a.m. EDT on Friday, the National Hurricane Center gave the two systems a remote chance of developing within two days and seven days, respectively, at 20 percent.
The remnants of former Tropical Storm Gordon continue to form about midway between the Lesser Antilles and the Azores. Strong westerly shear around 25 knots is moving showers and storms (convection) to the east of the weak forward Gordon surface low (1008 mb). Shear is expected to decrease this weekend, with surface waters unusually warm (about 28 degrees Celsius or 82°F) but the atmosphere fairly dry (moderate relative humidity about 45-50%). Still, former Gordon could briefly regain tropical storm status as it moves north.
A few hundred miles west of Gordon is a disturbance named Invest 96L, which has a surface low of 1007 mb over the same warm subtropical waters and experiences slightly less shear than former Gordon. However, the atmosphere here is also quite dry (mid-level humidity is about 40-45%) and convection is limited, so any development will be gradual.
This article was translated by Perla Marvell.
