Francine is becoming more and more organized

At 11:00 a.m. EDT Tuesday, Francine was located 425 miles (690 km) southwest of Morgan City, Louisiana, moving north-northeastward at 8 mph (13 km/h), with sustained winds of 65 mph (100 km/h) and a central pressure of 988 mb. Satellite imagery and Brownsville, Texas radar showed Francine had a modestly sized area of ​​severe thunderstorms that were becoming more organized. Heavy rainfall from the storm was affecting the coasts of northeastern Mexico and southern Texas.

Conditions were favorable for development, with record-warm ocean temperatures near 87°F (30.5°C), light wind shear of five to 10 knots, and a moist atmosphere. However, some dry air is west of the storm over Texas and Mexico, which disrupted development overnight.

Record warm water in the Gulf of Mexico

From Tuesday through Wednesday morning, Francine will benefit from record-warm ocean temperatures of around 30-30.5 degrees Celsius (86-87°F). This is about 1 degree Celsius (1.8°F) above the 1981-2010 average and is the warmest ever recorded for this time of year. Human-induced climate change has made this ocean warmth more than 200 times more likely along parts of Francine’s path, according to the Climate Central Ocean Shift Index (Fig. 1). These warm waters are evaporating near-record amounts of water vapor into the air, which will increase Francine’s heavy rainfall (see Tweet below).

Track prediction for Francine

There is some modest uncertainty in the track forecast, both cross-track (which part of the coast the storm will hit) and along-track (when it will hit). The forecast models have been shifting further east in their latest runs, increasing the threat to New Orleans. Heavy rainfall totals of over four inches are expected along much of the Gulf Coast, from western Louisiana to coastal Alabama.

Intensity forecast for Francine

Favorable conditions for Francine to intensify will persist through early Wednesday morning. Rapid intensification (defined as a 35 mph increase in winds in 24 hours) appears less likely than yesterday: The 12Z Tuesday run of the SHIPS model gave Francine only a 12% chance of rapidly intensifying to 35 mph in the 24 hours ending at 8 a.m. EDT Wednesday, which would bring it to Category 2 strength with 100 mph winds. The model gave Francine a 10% chance of becoming a major Cat 3 hurricane with 115 mph winds by Wednesday night.

Late Tuesday night into Wednesday, as Francine approaches the Louisiana coast, wind shear is expected to increase to the high range, 20-30 knots, and dry air on the western side of the storm could potentially attack the storm’s core, leading to weakening. There will also be less ocean heat energy available. These factors should cause Francine to stop intensifying six or more hours before landfall, and the highest intensity models predict that Francine will make landfall with sustained winds between 75-100 mph (120-160 kmph) – a Category 1 or 2 hurricane. Ensemble models suggest that as Francine moves further east (resulting in a greater threat to New Orleans), it could become a stronger storm (Fig. 2).

A devastating storm surge for Louisiana

A storm surge of 1 to 2 feet (0.6 to 1.2 m) was already observed along much of the Texas coast Tuesday morning, leading to some minor coastal flooding, according to NOAA’s Tides & Currents website. A much larger storm surge of five to 10 feet (1.5 to 3 m) is expected along the Louisiana coast, near and to the right of the center of landfall, leading to major flooding. The Louisiana coast is one of the most vulnerable locations in the world to high storm surges because of the large amount of shallow water off the coast. Francine’s angle of approach to the coast — from the south-southwest — makes it less of a storm surge threat to New Orleans than a storm approaching from the south or southeast.

High tide at Amerada Pass in central Louisiana is early Thursday morning at 3:30 a.m. EDT (7:30Z); low tide is Wednesday afternoon at 5:30 a.m. EDT (21:30Z). The difference in water level between high and low tide is about 1.5 feet (0.5 m), so the timing of Francine’s landfall will be a significant contributing factor in determining the amount of coastal flooding. The National Hurricane Center’s 11 a.m. EDT Tuesday forecast called for landfall around 6 a.m. EDT Wednesday, around the time of low tide. However, we should expect the timing of landfall to be off by as much as four hours. The timing of landfall from the 06Z Tuesday runs of our top six hurricane models had a nine-hour range, from 2-11 a.m. EDT.

History of Hurricanes in Louisiana

Louisiana has been hit by so many devastating hurricanes in recent years that Francine’s landfall will cause less damage than expected, since there is less to destroy. Twelve hurricanes have made landfall in the state since 2000. The most destructive were the two demon hurricanes of 2005, Katrina and Rita. Katrina’s $190 billion in damage (2024 USD) is still considered the most destructive weather disaster in world history; Rita’s $28 billion in damage was considered the fourth costliest hurricane in America at the time.

Five hurricanes have struck Louisiana in the past five years, including two Category 4 storms with 150 mph winds that were the strongest ever to hit the state west of the Mississippi, Laura in 2020 and Ida in 2021. (Hurricane Camille in August 1969 is the strongest hurricane ever to hit Louisiana; it was a Category 5 when it moved along the Louisiana coast east and north of the mouth of the Mississippi River on its way to its eventual landfall in Mississippi.) Laura caused $23 billion in damage (2024 USD) in Louisiana, and Ida cost the state $66 billion. Hurricane Zeta (2020, $5.3 billion) and Hurricane Delta (2020, $3.5 billion) were also very damaging.

Bob Henson contributed to this post.

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