BMS Tropical Update 9/20/2017 4 PM CDT

By: - September 20th, 2017

2017 Atlantic Hurricane Season Records Continue To Fall

The 2017 Atlantic hurricane season, which has already been memorable, continues to create long-lasting memories which will likely be talked about for decades. The newest talking point is Maria’s landfall at 6:35 this morning near Yabucoa, Puerto Rico. Maria arrived as a top end major Category 4 hurricane with maximum sustained winds of 155 mph and a pressure of 917 mb. Maria will likely be the strongest storm in terms of pressure to make landfall in Puerto Rico since 1928 – in terms of wind, it’s the second strongest. It is also the third most intense (by pressure) U.S. hurricane on record to make landfall behind Hurricane Camille, and the  Labor Day 1935 hurricane.

The statistics and images coming out of Puerto Rico indicate that Maria will likely be one of the largest natural catastrophes the island has ever experienced in terms of insured loss. But, I won’t dive into the devastation that has already occurred on the island, which is being covered extensively, but rather focus on the uncertainty of Maria’s long-term impact on the U.S. mainland.

Maria’s U.S. Mainland Threat

The geography of Puerto Rico has had a tremendous impact on Maria’s current intensity. The infrared satellite imagery above shows that the storm’s interaction with the high mountains has resulted in weakening, with a clear eye no longer visible. Unfortunately, this makes the storm no less dangerous, as winds well over 100 mph continue to beat the island. Torrential rainfall will remain as well, with totals nearing two feet in the higher terrain. Flash flooding and mudslides will be major issues for the next few days as Maria begins to move away from the island.

As Maria moves today toward the northwest, this weakening could influence the future track of the storm over the next week which, at this point, is still uncertain. A wobble south toward Hispaniola would result in a weaker system that may allow for a track farther west in the long term. The current forecast track takes the storm just north of Hispaniola, where the effect of land interaction would be minimal, thus keeping Maria on a more northwest track away from the East Coast of the U.S. next week.

The other complicating factor is the continued influence of Tropical Storm Jose, as discussed in my Monday update. Jose has already been a named storm for 15 days, which ties it for the 10th longest named storm since the beginning of the satellite era. Jose is still a large storm and, if it were not for Maria, would be a front-page news story. However, as I previously suggested, its insured impact has been minimal and similar to that of a nor’easter.

Currently Jose is doing another small loop off the New England coastline and is expected to continue to weaken over colder water as it moves back to the west later this week.

Reposting this image as the general ideas still holds from Monday thinking on overall pattern driving the northward turn of Maria.

Maria is expected to follow this weakness in the upper level ridge that Jose has created. However, the exact movement is a bit uncertain based on Maria’s trajectory away from Hispaniola and how far west Jose actually tracks. The general model guidance currently keeps Maria away from the East Coast. I do, however, expect the western edge of the National Hurricane Center’s cone of uncertainty to be very close to the coastline of North Carolina and Massachusetts as the five-day forecast cone expands northward over the next few days.

Right now, the forecast models have a bias that sometimes curve hurricanes northward  moving the hurricane to the northeast. If there is an error, it would result in a greater correction to the west with each model run.

Current long range track ensemble guidance from the American (GFS) and European (ECMWF) models. Most ensemble members keep Maria off the East Coast of the U.S. Some members however offer up landfall options all along the Northeast Coast of the U.S.

Currently, there is a 30% chance of U.S. landfall in New England per the American(GFS) ensemble model and a lower 10% chance from the ECMWF ensemble model. It should be noted, however, that cooler water temperatures and increasing wind shear will result in weakening of Maria as the storm moves northwest and then north this weekend. It would likely only be a Category 1 hurricane north of North Carolina.

Next Area Of Tropical Troubles

This is the next area to watch. This is the forecast valid for Oct 6th suggesting low pressure will be across the Western Caribbean

The next area to watch will be the western Caribbean, as the longer range models are suggesting tropical cyclogenesis in early October.

Back