Two tropical storms Marco and Laura are gathering steam and are expected to hit the gulf states in the middle of next week within 24 hours of each other. Marco is predicted to strengthen to a cat 1 Hurricane with max winds at 85 mph, but weakening a bit before landfall. Laura might strengthen to a cat 1 or cat 2 hurricane with max winds of 85 mph before she makes landfall, about 18 48 hours after Marco.
Twice before, in 1959 and 1933, two tropical storms have entered the Gulf at the same time. But never before have both been hurricanes. So, this will be the first double hurricane in the Gulf region.
Here is the projected path and timing of TS Marco. Landfall should occur off the coast of Texas around 8 p.m. Tuesday 1 p.m. Monday.
Update: Marco’s track has shifted eastwards quite a bit and is now forecast to make landfall in LA around 1 pm Monday.
Here is the projected path and timing of TS Laura. Landfall should occur off the coast of Louisiana around 2 p.m. Wednesday. Also, it will pass right over many Caribbean islands bringing rain, winds and misery to these weary islands.
There is still a good amount of uncertainty in the forecasts and both the track and the intensity can change over the next few days, depending on atmospheric and ocean conditions, interaction with land and shearing winds.
TS Laura forecast positions and max winds
INIT 22/0900Z 17.6N 65.5W 35 KT 40 MPH
12H 22/1800Z 18.2N 67.7W 40 KT 45 MPH
24H 23/0600Z 19.1N 71.0W 40 KT 45 MPH...INLAND
36H 23/1800Z 20.3N 74.6W 45 KT 50 MPH...INLAND
48H 24/0600Z 21.6N 78.3W 45 KT 50 MPH...INLAND
60H 24/1800Z 23.1N 81.8W 45 KT 50 MPH...INLAND
72H 25/0600Z 24.6N 84.7W 55 KT 65 MPH...OVER WATER
96H 26/0600Z 27.5N 89.5W 75 KT 85 MPH
120H 27/0600Z 31.0N 92.0W 55 KT 65 MPH...INLAND
TS Marco forecast positions and max winds
INIT 22/0900Z 19.6N 85.4W 40 KT 45 MPH
12H 22/1800Z 20.9N 86.1W 45 KT 50 MPH
24H 23/0600Z 22.5N 87.1W 50 KT 60 MPH
36H 23/1800Z 24.1N 88.3W 55 KT 65 MPH
48H 24/0600Z 25.7N 89.9W 60 KT 70 MPH
60H 24/1800Z 27.3N 91.3W 55 KT 65 MPH
72H 25/0600Z 28.3N 93.4W 50 KT 60 MPH
96H 26/0600Z 29.1N 96.2W 40 KT 45 MPH...INLAND
120H 27/0600Z 29.6N 97.8W 25 KT 30 MPH...POST-TROP/REMNT LOW
Forecast Models
Forecasts about storm track and intensity are based on computer models which are fed current atmospheric conditions and which calculate weather and storm conditions several days into the future. There are many such models and most graphs like the ones above are based on the average results from several models. Here is an example of the results for Laura from several models at the NOAA National Hurricane and Weather Forecast System (HWRS).
The HWRF model (purple line) seems to be an outlier, predicting a cat 4 Hurricane.
The Fujiwhara Effect
How the two storms will interact with each other as they get close to each other in the gulf waters is a complex matter and difficult to forecast this early. When two circulating storms get close to each other, they affect each other’s path and intensity, according to the Fujiwhara effect. There is a very small probability of them merging into a single (weaker) storm. More likely, they will remain separate but affect each other’s track. According to blog.weather.us/…, most likely, Laura would end up a little weaker and Marco would end up a lot weaker; Laura would head a bit more eastwards, while Marco would track a bit more to the west.
When tropical cyclones arrive in close proximity to another tropical cyclone, the interaction is detrimental for both storms. The reasons for this are twofold: destructive interference of low-level circulations and increase in upper-level wind shear. This is particularly true when one storm is much stronger than the other, as is forecast here by the ICON. In the lower levels of the atmosphere, two circulations spinning in the same direction near each other will “cancel each other out” where they meet.
Effect on trajectories due to potential interaction between Laura and Marco. The direction will shift from the red arrow to the purple arrow. blog.weather.us/...
Hurricane Hilary and tropical storm Irwin in 1993 doing the Fujiwhara dance -
Some Analysis and Guidance
From the 11:00 am NHC bulletin -
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Laura is moving into an environment of light shear, and combined with the somewhat improved organization it suggests the storm should strengthen.
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However, the forecast track takes the center over Hispaniola and then down the length of Cuba, which should at least slow any intensification.
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Over the Gulf of Mexico, warm water and a likely favorable shear environment should
allow Laura to become a hurricane, a scenario now supported by much of the guidance.
- Marco is forecast to strengthen to a hurricane as it moves into the southeastern Gulf of Mexico by tonight, and tropical storm conditions are expected over the northeastern coast of the Yucatan Peninsula and in extreme western Cuba.
- Marco is expected to move across the central Gulf of Mexico as a hurricane Sunday and approach the central Gulf Coast on Monday. There is an increasing risk of impacts from storm surge, winds, and heavy rainfall.
- From twitter.com/… - with #Marco getting stronger (and thus taller/deeper), expect rightward shifts in the forecast track, since steering currents are less westward at higher altitudes.
- At this time the model guidance suggests Laura and Marco will stay far enough apart to prevent direct interaction.
Satellite and radar imagery
Hurricane season 2020
Laura is the earliest named 12th Atlantic tropical cyclone on record; Marco holds the record for the the earliest 13th named storm.
The average number of named Atlantic storms per season is 11.3, so we have already blown past that average. And the hurricane season has barely started; mid-August through mid-October are the periods of the big hurricanes; earlier tropical storms tend to be few, weak and tend to stay offshore.
The 2020 Hurricane season so far is shown below (the chart also shows wind speeds for different storm categorizes).
North Atlantic tropical cyclones
Like most Atlantic tropical cyclones, Laura started as a tropical wave over western Africa.
The following map from NASA shows the tracks of all tropical cyclones during the 1985-2005 time period. The Pacific Ocean west of the International Date Line sees more tropical cyclones than any other basin, while there is almost no activity in the Atlantic Ocean south of the Equator. Tropical cyclones do not form around the equator.
Map of the cumulative tracks of all tropical cyclones during the 1985-2005 time period. Credit: NASA. www.nasa.gov/...
A large number of Atlantic hurricanes originate near the Cape Verde islands, off the west coast of Africa and are know as the “Cape Verde hurricanes.” These hurricanes form from a tropical wave that has passed over or near the Cape Verde islands after exiting the coast of West Africa. Hurricanes Dean (2007), Ivan (2004), Floyd (1999) Hugo (1989), Fran (1996), Isabelle (2003) are examples of Cape Verde hurricanes.
Atlantic Hurricane Season
According to weather.com/… , several factors contribute to the hurricane ramp-up that begins in August:
- African easterly waves are most developed, often serving as a seed for tropical storms and hurricanes to form.
- Saharan air layers, surges of dry air into the central and eastern Atlantic Basin that normally squelch tropical development in those areas, tend to give way by August as the parade of African easterly waves gradually add moisture. This effectively opens up more favorable real estate for tropical cyclone development.
- Vertical wind shear, the change in wind speed and/or direction with height, which can rip apart a tropical cyclone wannabe, tends to be low.
- Sea-surface temperatures rise toward a peak in early fall.
- Instability – the atmosphere's ability to generate convection (thunderstorms) to help initiate tropical cyclones – also rises toward an early fall peak.
Flying into the eye of the Hurricane
NOAA and the 53rd Weather Reconnaissance Squadron (53rd WRS) send aircraft with special instrumentation several times a day into the hurricane to make more precise and frequent measurements of parameters within hurricanes. The aircraft are equipped with radar and other instruments. Typically, they fly straight across the hurricane at altitudes between 1,000 feet to 10,000 feet. It sounds dangerous to fly into through the eye-wall of a hurricane swirling at 185 mph, but they have been doing so for decades with a near perfect record.
www.tropicaltidbits.com/… is an interesting site that plots the data from these recon flights in near real-time. Here is an example of the flight path across Laura today of the NOAA recon plane. The aircraft also drop dropsonde devices into the storm, which measure and relay vital signs of the hurricane as they fall down towards the ocean.
Hurricanes and Climate Change
Yes, hurricanes are not uncommon, but there is a link between climate change and increased hurricane intensities. According to this paper from Yale, How climate change is making hurricanes more dangerous -
There’s now evidence that the unnatural effects of human-caused global warming are already making hurricanes stronger and more destructive. The latest research shows the trend is likely to continue as long as the climate continues to warm.
Generally speaking, the warmer the water temperatures, the more heat energy is available and the higher the potential for tropical cyclones to develop. So it’s reasonable to assume that as humans continue to release planet-warming greenhouse gases, the likelihood of tropical cyclone activity increases. The conventional wisdom is that storm intensity will increase but storm frequency will either decrease or remain unchanged.
What’s next?
The Atlantic hurricane is just warming up. Keep an eye on two more potential storms in 7-10 days.
Epilogue
As is usually the case, forecasts will firm up in the next few days. For those in the path of the storm, please make preparations and stay safe. The best advise is to listen to forecasts and instructions from the NHC and local authorities, prepare for the worst and hope for the best.
Also, this will only make the COVID-19 situation worse, with limited testing and people possibly congregating in shelters.
We also wish some of this rainfall would head towards the west coast, but that never happens with Atlantic hurricanes anyways.
Further Reading
- National Hurricane center — www.nhc.noaa.gov
- weather.com/…
- Aircraft Reconnaissance — www.tropicaltidbits.com/…
- Real-time GOES-16 satellite imagery — rammb-slider.cira.colostate.edu/...
- Atlantic Basin Storm Names and Pronunciations — www.weather.gov/…
- The science behind this strange dance between hurricanes Hilary and Irwin — www.washingtonpost.com/...
- How To Tame a Hurricane — www.dailykos.com/…
- Hurricane Dorian Forecasts, Updates and Science - Part 2 (2019) — www.dailykos.com/…
