The East Pacific Basin's season began on May 15th, and they've got their first system on the third day. EastPac systems usually aren't covered on the main page, but this one is highly unusual in that it is forecast to enter the Atlantic basin... something that rarely occurs. The name will be Adrian when/if it gets to tropical storm strength, which looks very likely at this point. There is little climatology on such systems; tropical storms have occasionally wandered over to the coast near Guatemala; no hurricane has hit below the Mexican state of Chiapas, though. If this does happen it will be the first on record to do so.
Dependent on how strong it can get before crossing Central America, this system has the potential to be the first named storm on the Atlantic side as well. It is forecast to reach land late on Thursday, and be into the Caribbean by late Friday. The last named May system Atlantic side was Arlene in 1981, so it's been quite a few years since such an event. Watch this one; you may never see one like it again.

UPDATE: As of 11PM EDT (almost two hours ago, this is old info), TD 1E was upgraded to Adrian. The official forecast is essentially the same, with the track shifted ever-so-slightly to the right. They're still playing the storm conservatively, calling for a borderline TS/hurricane. A more clear and present danger is the flood threat, as Adrian is going cross some highlands and orographic effects will work to deluge some areas. Read Clark's post below for further explanation of that contingency. This storm is by its very nature already remarkable, and it has the potential to do plenty more.

-HF 0601Z 18May