Buckle your seat belts, hurricane season is here! If the formation of Arthur on the day before hurricane season officially starts is any indication, we are in for a strange and unusual season. Alma, the Eastern Pacific tropical storm that hit Nicaragua Thursday, fell apart over the high mountains of Honduras. The remnants reorganized over the Western Caribbean on Saturday morning and became Arthur. Had Alma maintained her identity as a tropical depression during the crossing, she would have kept her name. As it was, Alma died, had a posthumous sex change, and became reborn as a man named Arthur. Only two tropical storms since 1949 have made the crossing from Pacific to Atlantic and maintained at least tropical depression status during the crossing:Northeast Pacific Hurricane Cosme
became Atlantic Tropical Storm Allison
(June 1989).A Northeast Pacific tropical storm (September-October 1949)
became Atlantic Hurricane Storm #10
and made landfall in Texas.
Seven tropical cyclones have survived the crossing from Atlantic to Pacific. I'm not sure how many cases have occurred like Alma/Arthur, where the remnants of a tropical storm reform into a new cyclone in different ocean basin.Did Arthur form over land?
Arthur was also unusual in that the first advisory position for the storm was inland over northern Belize, about 30 miles from the ocean. Technically, the storm probably formed while the center was just offshore or right at the coast, but NHC did not name it until the center was already inland. There is one other case of NHC issuing its first advisory on a system while it was over land--Hurricane Agnes
, which became a tropical depression on June 14, 1972, while centered over the Yucatan Peninsula. Since the Yucatan is a relatively narrow strip of land with very warm ocean waters on three sides, one can form a tropical depression centered over land here in rare cases, when the large-scale atmospheric patterns are very favorable for tropical storm formation.Figure 1.
Track of Hurricane Agnes of 1972, which formed over the Yucatan Peninsula.The future of Arthur
The primary threat from Arthur is rain. Heavy rains of up to five inches
have fallen over portions of Belize and Southeast Mexico over the past 24 hours, and rainfall amounts of up to ten inches may accumulate in some regions. None of the models are bringing the center of Arthur over the Gulf of Mexico, so the storm should decay into a tropical depression later today, and then dissipate by Monday. What would really make for an odd season would be if Arthur died over Mexico, its remains drifted over the Eastern Pacific, then re-formed into Tropical Storm Boris. Some of the computer models were suggesting this yesterday, but are no longer doing so today.Would Arthur have been named 30 years ago?
Arthur is one of those weak, short-lived tropical storms that may not have been recognized as a named storm thirty or more years ago. Arthur was named primarily based on measurements from a buoy that didn't exist 30 years ago, and from measurements from the QuikSCAT satellite, which didn't exist until 1999. There was one ship report that was used, though, and ship reports were heavily relied upon in the old days to name tropical storms.