Powerful Hurricane Milton forms in the Gulf of Mexico, sweeps into Florida

After forming in the Bay of Campeche, Hurricane Milton underwent a remarkable period of rapid intensification with the central pressure falling from 1007 mb (29.74 inches of mercury, inHg) at 11:00 am EDT October 5th to 897 mb (26.49 inHg) at 8:00 pm EDT on October 7th, at which time Milton became the 5th most intense hurricane in the Atlantic Basin on record in terms of central pressure just behind Hurricane Rita (2005) on that list and only the 6th storm in the Atlantic to have a central pressure below 900 mb. In the process, Milton became the fastest Atlantic storm to intensify from a tropical depression to a Category 5 hurricane with maximum sustained increasing from 35 mph to 160 mph in just over 48 hours.

Similar to Hurricane Helene 11 days earlier, Milton’s formation appears to have been influenced by the Central American gyre, a seasonal area of low-pressure centered over Central America that results in a large-scale counterclockwise or cyclonic flow that can extend over the western Caribbean, southern Gulf of Mexico, including the Bay of Campeche, and far eastern Pacific. At the start of October, there was broad but generally disorganized thunderstorm activity within this area stretching from the western Caribbean and into the southern Gulf of Mexico. However, after a trough of low pressure rotated from the southeastern into the southwestern Gulf, thunderstorm activity began to consolidate in the southwestern Gulf in the Bay of Campeche. Persistent thunderstorm activity in this area then led to the formation of an area of low pressure, and by 10:00 am CDT on October 5th, the National Hurricane Center (NHC) determined that thunderstorm activity associated with this low was sufficiently organized to be classified a tropical depression. However, shortly thereafter at 12:25 pm CDT, NHC found winds of 40 mph, marking the formation of Tropical Storm Milton. At this time Milton was centered about 225 miles north-northeast of Veracruz, Mexico and drifting very slowly to the north-northeast at 3 mph.

Milton continued to slowly organize throughout the remainder of the day and into the early morning hours of the 6th. Later that morning, however, Milton strengthened into a strong tropical storm and following continued thunderstorm activity near the core, by 2:00 pm EDT, had reached hurricane intensity with maximum sustained winds of 80 mph. Milton proceeded to slowly strengthen with winds reaching 90 mph by 11:00 pm EDT at which time the center of the storm was located about 230 miles west-northwest of Progreso, Mexico in the Yucatan Peninsula and moving east at 7 mph. Several hours later the GPM core observatory overflew Milton for the first time.

This data visualization begins with surface rainfall estimates from NASA’s IMERG precipitation product in association with Milton in the Gulf of Mexico. The animation begins at 06:41 UTC (1:41 am CDT) 6 October 2024 just over 13 hours after Milton became a tropical storm and captures Milton transitioning from a more asymmetric structure with a large, north-south oriented rainband (orange and red arc) west of the center into a more compact system with most of the heavy rain (shown in red) concentrated nearer the center.

The 2nd part of the animation provides a detailed look at the structure and intensity of precipitation within Milton from the GPM Core Observatory when it overflew the storm around 7:11 UTC (2:11 a.m. CDT) October 7th when Milton was centered about 215 miles west-northwest of Progreso, Mexico. Surface rainfall estimates from the GPM Microwave Imager (GMI) show heavy (red areas) to intense (magenta) rain wrapping into the storm northeast of the center while GPM’s Dual-frequency Precipitation Radar (DPR) shows intense rain all throughout the entire northern half of the eyewall immediately north of the center.

The DPR can also provide a 3D perspective of the precipitation structure within the storm. Areas shaded in blue denote frozen precipitation aloft. The DPR shows that Milton has a very compact center as evidenced by the relatively small ring of echo tops (blue annulus) surrounding the center. The height of this precipitation is also a good indication of thunderstorm intensity, and the DPR shows several deep towers extending above 10 km in the northern part of Milton’s eyewall in association with the area of intense surface rain. Together these indicate intense thunderstorm activity is occurring in the northern eyewall. This results in large amounts of heat being released into the core of the storm and is usually a good indication of further strengthening.

At the time of the GPM overpass, Milton was still a Category 1 hurricane with NHC reporting sustained winds of 90 mph. However, it was soon after this time that Milton began the most impressive part of its rapid intensification with maximum sustained winds increasing to 100 mph by 4:00 am CDT, 125 mph by 7:00 am CDT, 155 mph by 10:00 am CDT, and 175 mph by 1:00 pm CDT. Milton went on to reach its peak wind speed of 180 mph by 4:00 pm CDT, which it maintained for about 6 hours until 10:00 pm CDT when the storm began to undergo an eyewall replacement cycle that lowered the peak intensity.

The GPM Core Observatory overflew Milton for the 2nd time at 06:41 UTC (1:41 am CDT) on October 8th when the center was passing to the north of the Yucatan Peninsula about 65 miles north-northeast of Progreso, Mexico. Although the DPR did not pass over the center of Milton, the GMI shows a very symmetric rain field around the center with heavy to intense rain occurring in all quadrants around the center. This uniformity reflects Milton’s powerful circulation, while the intense rain area suggests the storm is continuing to be sustained by strong heating within the core. At the time of this overpass. Milton was a high-end Category 4 storm with sustained winds reported at 155 mph by NHC.

A few hours after the GPM overpass, NHC reported that Milton had completed an eyewall replacement cycle. During an eyewall replacement cycle, a new outer eyewall forms outside of the current inner eyewall near the center, which weakens the inner eyewall and lowers the peak storm intensity. If the cycle is not inhibited and completes, the outer eyewall can contract and replace the original inner eyewall, allowing the storm to re-intensify, as was the case with Milton. Milton’s central pressure continued to rise until mid-morning on the 8th, but then, having recovered from its eyewall replacement, Milton began to re-intensify with surface pressures once again falling throughout the afternoon.

The GPM Core Observatory overflew Milton for the 3rd time at 19:41 UTC (2:41 pm CDT) on October 8th when the center was still passing to the north of the Yucatan Peninsula and entering the southeastern Gulf of Mexico about 520 miles southwest of Tampa, FL. Once again, GPM shows very intense rain rates occurring in all quadrants in the core of the storm, surrounded by a compact, symmetric area of heavy rain. This time the DPR was able to confirm the presence of very tall towers in the western eyewall where it was able to sample the core. Again, these features are all consistent with a strong and intensifying tropical cyclone. At the time of this overpass, Milton’s maximum sustained winds had recovered to 155 mph from a low of 145 mph earlier that same morning. Remarkably, Milton would continue to re-intensify into a Category 5 storm by 4:00 pm CDT with NHC reporting maximum sustained winds again reaching 165 mph and the central pressure falling to an incredible 902 mb by 7:00 pm CDT.

Milton was able to maintain Category 5 intensity overnight and into the early morning hours of the 9th, before finally beginning to feel the effects of increasing southwesterly wind shear, resulting from a large upper-level low pressure center over New England and a ridge of high pressure over the northern Caribbean. As a result, Milton began to both weaken and accelerate as it approached the west central coast of Florida. However, even before the center crossed the coast, Milton began to spawn tornadoes over the Florida Peninsula. Another overpass from the GPM Core Observatory at 19:11 UTC (3:11 pm EDT) on October 9th shows a large area of heavy to intense rain associated with Milton’s center off the west coast of Florida while the DPR shows several intense outer rainbands wrapping around the eastern side of the storm over the Florida Peninsula. In and around these rainbands, numerous supercell thunderstorms erupted, producing a slew of tornadoes. There was a total of 126 tornado warnings issued across the state on the 9th, the state record for a single day. At the time of the GPM overpass, Milton’s maximum sustained winds were reported at 130 mph by NHC with the center located about 110 miles due west of Ft. Myers, FL. Milton would go onto make landfall at 8:30 pm EDT at Siesta Key, FL as a Category 3 storm with maximum sustained winds of 120 mph.