Tropical Storm Philippe is likely to mix with Tropical Storm Rina in Atlantic, NHC says: What does that mean?

The National Hurricane Center continues to track Tropical Storm Philippe and Tropical Storm Rina – two systems just 500 nautical miles from one another in the Atlantic.

Tropical Storm Philippe formed over the weekend and is currently over 400 miles east of the northern Leeward Islands, the NHC said. On Friday, the storm had maximum sustained winds of 50 mph as it moved toward the west-northwest at 7 mph. Philippe is forecast to move slowly and remain east of the Leeward Islands over the next few days and could strengthen in the next few days. 

The NHC is also monitoring Tropical Storm Rina which formed over the central tropical Atlantic Thursday morning, becoming the 17th named storm of the 2023 Atlantic hurricane season

Rina is located around 1,000 miles east of the northern Leeward Islands and is expected to move northwestward across the central tropical Atlantic, putting it in proximity to the east of Tropical Storm Philippe's track, the NHC said. Rina strengthened slightly, topping wind speeds of 45 mph, but is expected to slowly weaken this weekend.  

Tropical Storm Philippe (left) and Tropical Storm Rina (right) are just 500 nautical miles apart from each other in the Atlantic, according to the National Hurricane Center. (Photo: NOAA)

Could Tropical Storm Philippe and Tropical Storm Rina mix?

NHC forecasters said Friday that Philippe and Rina are expected to continue to interact through the weekend. Early next week, Rina is expected to "separate from Philippe as a mid-level ridge builds over the subtropical central Atlantic." 

While they are several hundred miles apart, "they are in considerably better agreement (Friday) compared to the past couple of days," forecasters added. 

Earlier on Friday, forecasters said movement through the end of the weekend is likely to be dictated by "binary interaction" with Tropical Storm Rina to the east. Binary interaction is another term for the Fujiwhara effect, a weather phenomenon that happens when two nearby storms move around each other, according to the National Weather Service

Some models show little to no interaction between the two storms, but forecasters said since the storms are only located 500 nautical miles from one another, "some degree of interaction is likely." The models showing no interaction are outliers at this time, according to the NHC. 

If two hurricanes spinning in the same direction pass close enough to each other, they "begin an intense dance around their common center," the NWS said. The weaker or smaller storm will orbit the bigger one, eventually crashing into its vortex to be absorbed. If the storms are closer in strength, they can reach a common point and merge, or just spin around each other before "shooting off" on their own paths. 

"The bulk of the track guidance indicates that Philippe will dip farther toward the southwest during the next 48 hours due to Rina's influence, but then turn toward the northwest and north on days 3 through 5 as a mid-tropospheric high builds over the central Atlantic," forecasters said. 

There continues to be "larger-than-normal" uncertainty in Philippe's future track at this time. 

Neither storm is expected to have an impact on the U.S. or Florida at this time. 

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