Discussion: Several new issues have emerged in the tropics – all of which could impact the U.S. The first is Tropical Disturbance 94L. This system will enter the Bay of Campeche as a low-pressure system today. Over the warm waters of this region, 94L should have no problem strengthening to a tropical depression in 24 hours and a tropical storm within 36-48 hours. Latest tropical cyclone model guidance indicates this system will travel north over the warmer-than-normal (already very warm) western Gulf of Mexico (Fig. 1). A tropical storm making landfall somewhere in the central or southern Texas coastline Monday night or early Tuesday is implied by both tropical cyclone models and ECM/GFS operational models. Although intensity forecasts do not indicate a hurricane (Fig. 2), the warmer-than-normal western Gulf waters indicate a hurricane is certainly possible. This system is a slow-mover and NOAA/WPC have already issued 10-20 in. rainfall forecasts for the Texas/Louisiana coastal region for the next several days and up to one week (Fig. 3).
Fig. 1-2: Tropical cyclone models tracks and intensity forecast for 94L.
Fig. 3: NOAA/WPC 7-day rainfall forecast.
Models have been off-and-on forecasting a potential significant tropical cyclone emerging east of the Bahamas early-to-middle next week and transiting northwestward into the Mid-Atlantic Coast. Forecast models are more consistent with this possibility AND the potential track is across warmer-than-normal waters supporting (the GFS forecast) of a possible hurricane with excessive rainfall/high wind impacts late next week and weekend into the Mid-Atlantic region (Fig. 4).
Finally, a tropical disturbance is forecast to emerge off the West Africa Coast in about 36 hours. The ECM indicates this system will quickly become a tropical storm, travel due west to west-northwest, likely gain hurricane intensity and in 10 days be located just northeast of Puerto Rico and heading for the U.S. (Fig. 5).
Of course, a busy tropical pattern means warm high-pressure ridging persists northwest and north of the tropical threats. Consequently, the GFS (model) is very warm to hot for the next couple weeks across the Central and into the East U.S. (Fig. 6). To close September, the ECM (model) indicates lingering very warm high-pressure on the East Coast (Fig. 7).
Fig. 4: GFS is consistent forecast heavy to excessive rainfall in the Mid-Atlantic region late next week due to a land-falling tropical cyclone.
Fig. 5: ECM day-10 forecast of tropical system crossing the North Atlantic tropics, likely a hurricane and moving west-northwest.
Fig. 6: GFS 15-day temperature anomaly forecast for the U.S. indicates very warm to hot weather Central and East!
Fig. 7: ECM days 16-20 upper air forecast indicates a warm upper ridge resides on the East Coast to close September.