Thursday September 7

This evening the National Hurricane Center shifted their forecast track for Hurricane Irma just west of Miami on Sunday. This was actually in response the the storm NOT passing directly over the Turks and Caicos Islands, but about 55 miles south. That difference in track can make or break the impacts on south Florida. At this point it leads to the idea of a later turn and thus inland track west of Miami. That would be over my parent’s property, there family, and a stronger hit for many of my friends in the region.  Some wiggle room allows form a shift of the track but the margin is getting smaller a this is two days away.

SUMMARY OF 800 PM EDT…0000 UTC…INFORMATION
———————————————-
LOCATION…21.1N 71.8W
ABOUT 55 MI…85 KM WSW OF GRAND TURK ISLAND
ABOUT 90 MI…145 KM E OF GREAT INAGUA ISLAND
MAXIMUM SUSTAINED WINDS…175 MPH Gusts to 210 mph
PRESENT MOVEMENT…WNW OR 285 DEGREES AT 16 MPH…26 KM/H
MINIMUM CENTRAL PRESSURE…919 MB…27.14 INCHES

The results of a track inland would lead to these impacts:

  • Maximum hit on Miami and the east coast of Florida remaining on the strong side of the eye wall (see below)
  • Longer path inland on Florida would weaken the storm faster, and less devastation for Georgia and South Carolina than if it stayed over water.
  • The potential secondary storm surge up the coast and into the Chesapeake Bay would be less dramatic. However there will still be a rise in water.

Threats to south Florida

  • Rain: 5 to 20 inches 
  • Storm Surge: 5 to 10 feet
  • Winds: Over 140 mph
  • Tornados at landfall

Hurricane Structure Breakdown

It is important to look at a tropical system with forward motion.

  • The Right Side is the stronger side as the outer-clockwise wind flow moves with the forward speed. Plus it comes off of the water. So the storm surge will be highest here.
  • The Left Side is the weaker side as the winds are moving opposite the forward speed. Also, the wind off of the land. The storm surge drops off dramatically farther to the left
  • The eye wall itself is where the strongest winds are located. The winds decrease farther away from the center. Irma is described as having hurricane force winds 60 miles from the center. That means the eye wall has 175 mph winds, but 60 miles away the winds are 75 mph. The tropical storm force winds (over 40 mph) extend 185 miles away from the center in all directions.

 

Forecast Model Updates

Please note there there will likely be a little more wiggle to the track reaching south Florida. There is still a 50 mile spread of the eye track between the HWRF, GFS, and European Models (just to name a few).

The GFS  Model has been the most consistent with this storm and has shifted back west of Miami with the track Sunday morning.

HWRF Model still has the eye along the coast, passing the edge over Miami

European ECMWF has shifted farther west with a hit near Marathon Key

 

Animation

Here is the GFS Model solution showing how this inland track then rides along the coast farther north. This may be the worst case scenario! Note the push inland from Georgia. This will miss Maryland, but some storm surge is likely due to the large wave memory and the easterly flow from High Pressure off New England.

Farther North: Chesapeake Bay Gets Some Surge

Note: If Irma goes inland west of Miami, then the chance for a surge into the Chesapeake Bay diminishes

Here in the Mid Atlantic the impacts will be secondary. I see the potential for an indirect storm surge up The Chesapeake Bay. The storm should go inland well to our south. However the wave memory of a former 185 mph wind storm PLUS the High Pressure off of New England will help to pile the water onshore, and eventually up the Bay. Water levels will rise Monday, but the highest water will be after a few high tide cycles can not drain… So the highest water will be Tuesday and Wednesday. It is too early to say how high the water will reach. At this time I DO NOT see a repeat of Isabel’s surge, but this is worth paying attention to closely. We should have that impact better known by Sunday.

Arrival Time

Tropical Storm Force Winds extend 185 miles from the center, the first effects on Florida will arrive Saturday ahead of the eye expects Sunday.

Watches and Warnings

The National Hurricane Center point is west of the coast but please the entire cone as the potential for the storm just like the track today was 55 miles south of the expected path.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Storm Surge Watch is in effect for…
* Jupiter Inlet southward around the Florida peninsula to Bonita
Beach
* Florida Keys

A Hurricane Warning is in effect for…
* Dominican Republic from Cabo Frances Viejo to the northern border
with Haiti
* Haiti from the northern border with the Dominican Republic to Le
Mole St. Nicholas
* Southeastern Bahamas and the Turks and Caicos Islands
* Cuban provinces of Camaguey, Ciego de Avila, Sancti Spiritus, and
Villa Clara
* Central Bahamas
* Northwestern Bahamas

A Hurricane Watch is in effect for…
* Jupiter Inlet southward around the Florida peninsula to Bonita
Beach
* Florida Keys
* Lake Okeechobee
* Florida Bay
* Cuban provinces of Guantanamo, Holguin, Las Tunas and Matanzas.

 

Keep on Trekking

Continue to be part of our Maryland Trek and Support Cool Kids Campaign. This was our best event yet and we want the message to carry throughout the year.

Proceeds go to programs that help children and their families ensuring cancer treatment.

 

 

Please share your thoughts, best weather pics/video, or just keep in touch via social media

 

Get the award winning Kid Weather App I made with my oldest son and support our love for science, weather, and technology. Our 3 year anniversary of the release and our contribution to STEM education is this November. It has been downloaded in 60 countries, and works in both temperature scales. With your support we can expand on the fun introduction to science and real weather.