The end of June saw unusually favorable conditions in the tropical Atlantic for cyclonogenesis. One tropical wave took advantage of these conditions and began to organize. By June 27, the storm was quickly approaching the Windward Islands and was producing gale force winds, but did not have the closed circulation necessary to be a tropical storm. Its low latitude and fast forward speed toward the west prevented it from taking the final step to development at first. Land interaction compounded these issues the next day when it entered the Caribbean; it was so far south that it was skirting the northern coast of South America.
It was not until a few days later that the system moved into the southwestern Caribbean and again had an opportunity to develop. At last, on July 1, it was designted Tropical Storm Bonnie. By that time, the storm was less than a day from reaching land once again. Bonnie did strengthen somewhat during the day into a moderate tropical storm before making landfall near the border between Nicaragua and Costa Rica. Landfalls this far south in central America are fairly rare, particularly in this part of hurricane season; Bonnie became at the time the southernmost central America landfall for any July system of at least tropical storm strength.
The storm wasn't disturbed much by its passage over Nicaragua since it encountered mostly low-lying land. In fact, the center passed over Lake Nicaragua, which seemed to help preserve the circulation. On July 2, Bonnie emerged as a tropical cyclone into the eastern Pacific. Since the storm remained intact upon crossing from the Atlantic to the Pacific, it retained the name "Bonnie". This was the first time a storm crossed over and kept its name since Hurricane Otto in 2016. Conditions were favorable over water, and the system began to strengthen again. The cyclone developed an unusually large blob of convection to the west of the center that night, but its displacement from the center precluded rapid intensification.
Bonnie was a large cyclone over warm waters, so the wind shear wasn't enough to prevent it from gradually gaining strength. On July 3, it strengthened to a hurricane. The eyewall continued to get better defined and and eye even appeared on July 4, when the system was upgraded to a category 2. It peaked the next day as a category 3 major hurricane. Meanwhile, the storm was on a very steady heading toward the west-northwest. Soon after, however, wind shear and cooler waters began to weaken the system. It slowly decayed for several days before becoming post-tropical on July 9. The remnants dissipatd a few more days after that.
The above image shows Bonnie just before landfall in central America. After traversing the narrow isthmus, it emerged into the Eastern Pacific intact.
Bonnie achieved major hurricane status after moving into the Pacific.
*Note: Bonnie is listed as a tropical storm active from July 1-2 in the post's title because this was the peak intensity it achieved while in the Atlantic basin. It only became a hurricane in the eastern Pacific and is therefore counted as a tropical storm in season totals.
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