Hurricane Ian roared into the Gulf of Mexico Tuesday morning as a major category 3 hurricane, relatively undamaged by its brief traverse of western Cuba. While the worst-case prospect of the hurricane’s hitting just north of Tampa and inundating Tampa Bay with a massive storm surge is looking less likely, Ian was intensifying on Wednesday afternoon and is expected to deliver a punishing landfall as a slow-moving major hurricane in western Florida on Wednesday evening.

Ian delivers devastating blow to Cuba

Hurricane Ian delivered a harsh blow to western Cuba Tuesday morning after making landfall to the south of Pinar del Rio, Cuba’s 10th-largest city, with a population of 143,000. Ian’s landfall at approximately 4:30 a.m. EDT came as a category 3 hurricane with 125 mph winds and a 947 mb central pressure, just two hours after it became the second major hurricane of the 2022 Atlantic hurricane season. Ian likely brought a highly destructive storm surge of 9 – 14 feet to the coast of Cuba; wind and flash-flood damage was severe along the path of the hurricane, according to initial reports. The western edge of the eye passed over Pinar del Rio, and that city received an intense battering from Ian’s left (weaker) eyewall. A wind gust of 114 mph was recorded as the hurricane passed. Fortunately, the eyewall of Ian missed the capital of Havana, since the eye passed about 70 miles to the west of the city. The peak wind gust measured in Havana Tuesday morning was 45 mph, at 11:50 a.m. EDT.

It took Ian about six hours to cross over Cuba and enter the Gulf of Mexico, and the inner core survived the crossing intact – though the central pressure of the storm rose 16 mb, and the winds weakened by 10 mph. On Tuesday afternoon, the hurricane was bringing heavy rains and strong winds to much of South Florida and the Keys; the highest winds at Key West Tuesday morning were sustained at 33 mph, gusting to 48 mph, between 10 and 11 a.m. EDT.

Highly destructive storm surge will hit much of western Florida coast

The good news: the recent shift in model guidance toward a landfall farther to the south decreases the odds that Tampa Bay will see a landfall to its north. If the center of Ian comes ashore to the south of Tampa Bay, the counter-clockwise circulation of the storm will blow offshore, pushing water out of the bay. In this scenario, Tampa Bay would avoid a worst-case storm surge scenario where the powerful right-front quadrant winds drive a destructive 5 – 10-foot surge into the bay. However, once Ian moves northward over the Florida Peninsula to a point north of Tampa Bay’s latitude, the circulation of the hurricane will begin piling water into the bay, resulting in a significant storm surge that will last through multiple high tide cycles late Thursday and into Friday. As of 1 p.m. EDT Tuesday, the National Hurricane Center had reduced itsstorm surge forecast for Tampa Bay to 4 – 7 feet.

The bad news: a large stretch of heavily developed Florida coast, from Sarasota to Fort Myers, will potentially receive a highly destructive storm surge from the right-front quadrant of a slow-moving major hurricane. One area of most concern at present is Punta Gorda and Port Charlotte, which lie on Charlotte Harbor. This portion of the coast is forecast to receive 8 – 12 feet of storm surge. Unfortunately, the two rivers flowing into Charlotte Harbor, the Peace and Myakka, are already at minor flood stage from heavy rains earlier in the month. The heavy rains from Ian will increase the flooding of these rivers, causing a compound flood event in Charlotte Harbor that will boost the storm surge damage to Punta Gorda and Port Charlotte.

Storm surge flooding this week will be augmented by some of the highest tides of the month, the “king tides,” occurring because of the new moon on Sunday. Tidal range between high and low tide is about 2 – 2.5 feet at Tampa, and the highest tides this week are between 3 – 5 a.m. EDT Wednesday through Saturday. At Fort Myers, the tidal range is just over one foot this week, so the timing of Ian’s surge with respect to the tidal cycle is less important than for Tampa Bay.

A large and powerful hurricane, Ian has a counter-clockwise circulation that will also create destructive storm surge flooding on the east coast of Florida, and northwards along the Georgia coast. This storm surge flooding will also be augmented by the king tides.

You can observe the current storm surge levels at the NOAA Tides and Currents Hurricane Ian QuickLook page.

Ian likely to be a devastating rain-maker

Ian is now expected to move slowly northward across the Florida peninsula from late Wednesday into early Friday, which could bring massive amounts of rain to central and northern parts of the peninsula.

Rain bands just north of Ian were already affecting the southern half of Florida on Monday night, with steadier rain and heavier embedded showers and thunderstorms increasing on Tuesday morning. Rainfall totals for the 24-hour period ending Tuesday morning, as recorded by CoCoRaHS volunteers, ranged from 0.5 – 2 inches in Tampa bay area, 2 – 5 inches along the southeast Florida coast, and 3 – 7 inches in the Florida Keys. A total of 7.20 inches was reported in the Middle Keys near Islamorada.

The heaviest rains on Wednesday and Thursday will be in a broad corridor running from south-southwest to north-northeast along and just north of Ian’s path. Along this corridor, widespread 10-15-inch totals can be expected, with pockets of 15 – 25 inches quite possible, especially near and just inland from Ian’s landfall location. Even these amounts could be exceeded in some areas, as suggested in output from the GFS (see tweet above) and other models, but keep in mind that any model projections should be taken as general guidelines rather than literal point forecasts. Most of the southern half of Florida has received 5 – 10 inches or more of rainfall in the past two weeks, and several rivers from southwest to northeast Florida – along Ian’s general expected track – are already at the minor-flooding stage.

Accompanying the rains in Ian’s rain bands will be a few tornadoes: NOAA’s Storm Prediction Center has slight-risk areas for the next three days over portions of Florida. Though increasing wind shear will weaken Ian, it could make things worse for the hurricane’s tornado threat.

Track forecast for Ian:  Small angles make big differences

Ian is expected to continue on a general northward track through this week, pulled northward by an upper-level storm system now departing the eastern United States. However, there’s been a rightward shift in the forecasts of the angle of that northward track over the past 24 hours, and this shift has big implications for Ian’s impacts. Because Ian is approaching the coast at such a sharp angle, a relatively small shift to the left or right in Ian’s track can push the landfall location dozens of miles northward or southward along the coast, which in turn can alter the storm-surge potential and other impacts. Any remaining meteorological uncertainty in where Ian will track is only made worse by the unavoidable confluence of storm path and coastline geography. As a result, residents throughout a large swath of coastal southwest Florida must be ready to act quickly in response to the latest warnings and official evacuation notices on Ian. Although landfall has grown increasingly likely to occur from Tampa southward, the lower-probability outcome for Tampa Bay – a landfall just north of the area – cannot yet be completely ruled out.

The leading forecast models had differed sharply for days on Ian’s ultimate destination (the GFS leaning toward the Florida Panhandle, the ECMWF and UKMET leaning more toward Tampa). These models have now come into strong agreement on a landfall on Florida’s Gulf Coast, most likely between Tampa Bay and Charlotte Harbor. Hurricane watches were extended southward from Bonita Beach (just south of the Fort Myers area) to Chokoloskee at 11 a.m. Tuesday. The rightward lean in Ian’s latest track forecast means Ian will likely hit the coast sooner than earlier thought – most likely on Wednesday night – and it will arrive as a stronger storm than previously expected, most likely as a major hurricane, as it will have less time to be affected by the dry air and wind shear now heading toward the area.

The steering flow will temporarily ease from Wednesday to Thursday, allowing Ian to slow significantly as it moves into west-central Florida before resuming a general northward movement. This semi-stall will prolong the period of onshore flow and coastal flooding over southwest Florida, and it will greatly boost Ian’s rainfall potential, as noted above.

Intensity forecast for Ian

Now that Ian is in the Gulf of Mexico, the hurricane no longer has ideal conditions for intensification. Though the waters beneath the storm remain very warm, near 30 degrees Celsius (86°F), and have a high heat content, Ian is now feeling the effects of an upper-level trough of low pressure to its northwest. This trough was bringing southwesterly upper-level winds that were creating a moderate 10 – 20 knots of wind shear on Tuesday afternoon. The trough was also bringing drier air with a mid-level relative humidity of 65% to the hurricane’s west side. Even so, Ian was showing distinct signs of strengthening early Tuesday afternoon, and the increased upper-level winds may help at first by providing an outflow jet before the shear increases dramatically.

The 12Z Tuesday run of the SHIPS model predicted that wind shear would steadily rise until Ian makes landfall, reaching a high 20 – 30 knots on Wednesday. The higher wind shear may be able to drive the dry air to the west into the core of the hurricane before it makes landfall, significantly weakening it. However, it currently appears that Ian has a strong enough inner core that it will be able to keep it intact against the wind shear, if landfall occurs on the southern edge of the cone of uncertainty, farther to the south. A track farther to the north, resulting in a landfall delayed until Thursday, would give the shear and dry air a longer period to attack the hurricane, increasing the odds of significant weakening before landfall.

Ian’s sustained winds had increased to 120 mph as of 1 p.m. EDT Tuesday. The 11 a.m. Tuesday NHC forecast predicted Ian would peak as a category 4 hurricane with 130-mph sustained winds from Tuesday night through Wednesday morning, then weaken slightly to a 125-mph category 3 storm by 8 p.m. Wednesday near the time of landfall in western Florida. The 12Z Tuesday DTOPS model had a 30% chance that Ian would become a high-end Cat 4 with 150 mph winds by 8 a.m. Wednesday, and a 20% chance of hitting category 5 strength by that time. The 12Z Tuesday SHIPS model had similar probabilities, and an 8% chance that Ian would become a high-end category 5 hurricane with 175 mph winds.

Steering currents are now weakening for Ian. The hurricane crossed Cuba with a forward speed of 12 mph, but that speed slowed to 10 mph as it emerged from the coast of Cuba. Ian is expected to slow to about 5 mph by Wednesday afternoon. This very slow motion will allow Ian to pile up a large and damaging storm surge along the west coast of Florida. This surge will last through multiple high-tide cycles, allowing it to penetrate far inland up narrow creeks and estuaries. Moreover, the slow motion of Ian near the coast will allow the storm to dump prodigious amounts of rainfall, and subject the coast to an extended period of battering winds, increasing the wind damage.

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