Puerto Vallarta, Mexico - Hurricane Simon shifted track slightly on Sunday and was forecast to skirt Mexico's coast without making landfall, while packing heavy rain and severe winds.

The cyclone – a Category 4 storm on the five-point Saffir-Simpson scale – is moving slowly and remained dangerous.

Weather reports had initially forecast a landfall around midday local time Sunday, but data gathered by hurricane hunter aircraft indicated the cyclone was moving slower and would only reach about 9 miles off the coast of Jalisco state.

Even if a direct landfall does not occur, "all the cyclone's cloud bands, or the intense part of the cyclone, will still be affecting" coastal communities, Fabian Vazquez, director of Mexico's meteorological service, told AFP.

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"We're going to have very severe effects, especially from wind along the coast," with waves of up to 30 feet)and exceptionally heavy rainfall, he added.

Simon is the latest in a busy hurricane season in the Pacific, where the powerful El Nino ocean warming phenomenon is weakening wind shear, allowing the storms to gain in strength. By contrast, El Nino has helped keep the Atlantic hurricane season relatively quiet.

AFP journalists in tourist hotspot Puerto Vallarta, in the storm's forecast path, observed overcast skies early Sunday, with heavier clouds building over the sea and mountains as a light rain was falling.

Businesses boarded up windows and doors, some spray-painting messages such as "Simon says: 'Everything will be fine,'" a reference to the popular game in which children follow instructions; and "Simon, be brief, be peaceful" alongside a drawing of a shark and smiley faces.

A couple strolled along the waterfront promenade, which was guarded by troops. An occasional jogger also took the opportunity to get out of the house.

The latest report from the US National Hurricane Center put Simon's sustained winds at 143 miles per hour, with the storm moving at roughly 7 miles per hour.

Simon has remained "nearly stationary" off Mexico's coast, Boris Comi, a meteorologist with Jalisco's civil protection agency, said. That means it can "generate more rain over a longer period," which "puts the population at greater risk."