One more area of disturbed weather in the eastern tropical Atlantic is under investigation as we continue progressing through the peak of Atlantic hurricane season.
Gulf of Mexico disturbance aimed at Texas
An area of thunderstorms over the western Gulf of Mexico has the potential to become a major rainmaker for parts of East Texas. While the National Hurricane Center gives it a 10 percent chance of becoming a named storm, it could produce excessive rainfall totals.
Forecasters have begun to stress that this system could become dangerous even if it is not a named storm. Inland flooding has been the leading cause of fatalities from tropical systems in recent years.
Areas of heavy rain were already approaching the Texas coast on Monday, but the heaviest and most widespread downpours are forecast midweek.
The disturbance will move ashore somewhere between Matagorda Bay and Port Arthur on Tuesday evening, bringing areas of very heavy rainfall. Atmospheric moisture content is predicted to reach two or three times above average values. Indications suggest the tropical rainstorm will stick around through at least Wednesday night, if not Thursday, moving very little.
Ingredients may come together for a potentially high-impact flood event over highly populous parts of Gulf Coastal Texas, including Houston. A widespread three to seven inches is possible, but the European model, shown above, indicates the potential for localized higher amounts into the double digits.
According to the European model, the amount of water vapor loaded into the atmosphere will be exceptionally high (as illustrated in the animation below which shows total precipitable water, a measure of atmospheric moisture), at levels rarely observed in the region.
In this sort of environment, rainfall rates of two to three inches per hour are possible beneath the heaviest downpours. Flash flooding can evolve quickly in this sort of atmospheric setup. The National Weather Service in Houston has indicated it is likely to hoist a flash-flood watch to account for this potential.
Hurricane Humberto to track toward Bermuda, but East Coast should monitor
Humberto became a hurricane Sunday night, the third of the 2019 Atlantic hurricane season. It’s located east-southeast of the Florida/Georgia border, and is just over 700 miles west of Bermuda. Maximum sustained winds are around 85 mph.
Humberto’s trek through the northwestern Bahamas was very similar to Hurricane Dorian’s, and it drenched hard-hit residents with heavy rainfall but spared them much wind or surge.
Humberto is continuing to gather strength, the first hints of an eye appearing on infrared satellite imagery. It is now forecast to become a Category 3 hurricane between Tuesday and Wednesday.
The majority of weather models take Humberto generally northeastward by Wednesday, coming close to Bermuda on Wednesday night or Thursday morning.
After its closest pass to Bermuda, Humberto may try to slip a bit to the north or even northwest briefly. A few model simulations even bring it back uncomfortably close to the U.S. East Coast, though still offshore. The National Hurricane Center said it has “lower-than-normal confidence in the track forecast” later this week.
Most likely it will remain well out to sea and transition into a post-tropical storm, but residents along the East Coast should continue monitoring.
Elsewhere in the Atlantic
The National Hurricane Center is monitoring an area of storminess likely to develop in the next few days east of the Lesser Antilles. While it is likely to strengthen, perhaps into a tropical storm or greater, it appears to pose little threat to land at this point.
The eastern tropical Pacific: Foreshadowing what’s next for the tropical Atlantic?
We wrote last week about how atmospheric features known as the Madden-Julian Oscillation and an approaching convectively coupled Kelvin wave could line up to give us a turbo boost in tropical development late in September into early October. Those favorable parameters are stationed over the eastern Pacific Ocean, where multiple areas of disturbed weather and storminess have flared up, as shown below:
There is now a Category 3 hurricane and three areas of disturbed weather under investigation within about 2,000 miles in the eastern Pacific. While it’s impossible to predict individual storms more than a week in advance, the effects of the features in the Pacific forecast to cycle into the Atlantic should not be ignored. The tropical Atlantic may be in for a brief two-week roller coaster ride late September into early October.