A Tropical Storm Watch was issued today for Bermuda as Hurricane Franklin travelled north rated at the Category 4 level.

The system could strengthen further today, but it is expected to weaken gradually later tomorrow, the latest forecast said.

At 6pm, the Bermuda Weather Service said Franklin’s closest point of approach within the next three days was predicted to be 190 miles to the northwest at 11am on Wednesday.

The BWS added that the hurricane could move closer to the island after that time.

The NHC said todaythat Franklin had become the first major hurricane of this year’s Atlantic hurricane season.

Its midday update explained: “A Tropical Storm Watch means that tropical storm conditions are possible within the watch area, generally within 48 hours.”

By 6pm, Franklin was moving towards the north at about 9mph.

Government officials were also watching the approach of Tropical Storm Idalia, churning through the Gulf of Mexico and expected to develop as a hurricane as it approached the northwest coast of Florida.

Projections have Idalia crossing the Florida peninsula and potentially tracking towards Bermuda’s north by the weekend.

The NHC said Franklin’s northward to north-northeastward motion, with a slightly faster forward speed, was expected over the next few days.

“On the forecast track, the centre of Franklin is expected to pass well west of Bermuda on Wednesday.”

The update said: “Based on data from the Air Force Reserve hurricane hunter aircraft, maximum sustained winds have increased to near 145mph with higher gusts.

“Franklin is a Category 4 hurricane on the Saffir-Simpson Hurricane Wind Scale.

“Additional strengthening is possible today, but gradual weakening is expected to begin later Tuesday.

“Hurricane-force winds extend outward up to 35 miles from the centre and tropical storm-force winds extend outward up to 150 miles.”

It added: “Swells, life-threatening surf and rip currents generated by Franklin are beginning to affect Bermuda and the southeast United States and are expected to spread northward along the East Coast of the United States, Atlantic Canada, during the next couple of days.”

The update said that tropical storm conditions were possible in the watch area by Wednesday morning.

A forecast from the BWS this morning said: “Tuesday sees the approach of then major Hurricane Franklin though latest guidance has pushed back the onset of winds slightly further.

“An outflow boundary ahead of Franklin is now poised to move over the area on Tuesday bringing a few showers with the low chance of thunder per instability indices.

“A few additional showers then pass on Wednesday as Franklin passes by to our distant north.

“It should be noted that outflow boundaries are difficult to forecast, and showers and thunderstorms may develop on Tuesday to a greater extent than currently forecast.

“The latest National Hurricane Centre forecast now has Franklin passing even further to our north on Wednesday and the result is a much weaker wind forecast for both days.”

The BWS said winds could increase to up to 35mph tomorrow evening, with gusts of between 40 and 52mph in line with boundary layers.

Its forecast added: “These winds then likely carry over into Wednesday with the extreme northern parts of the marine area possibly seeing brief tropical storm force winds.

“If the current trend continues, tropical storm-force wind may pass well outside of our marine area.”

It said winds were expected to ease by Wednesday evening while “gradually veering westerly”.

The forecast added: “Seas rapidly build very rough overnight on Tuesday peaking near 16ft and then rapidly ease later on Wednesday.”

Its long term forecast noted that Tropical Storm Idalia — not considered a threat at this time — was expected to approach on Friday.

The BWS said: “Winds gradually ease moderate on Thursday before increasing moderate to strong on Friday.

“Later on Friday potentially sees the return of wet weather as Idalia approaches from the northwest.

“Seas ramp once more to a rough state.”

• UPDATE: This article has been updated with the latest available information.