Thursday, 6 October 2016

Typhoon Matthew- maintaining major hurricane intensity despite making landfall twice

Dangerous Hurricane Matthew Strengthens in Record Hot Environment — May hit Florida Twice

5 October, 2016

Hurricane Matthew has already been a storm for the record books. Matthew was the lowest latitude Category 5 storm to form on record in the Atlantic basin. An achievement that bears testament to the amount of heat energy the storm was feeding on — as higher latitude storms can better leverage the Earth’s spin to increase wind speed. It was the longest lasting Category 4-5 storm on record in the Caribbean. And it produced the highest accumulated cyclone energy (ACE) of any hurricane on record for that sea.

(Matthew is predicted to track along the Eastern Seaboard from Central Florida through Georgia as a major hurricane on Friday and Saturday. After this first predicted strike as a major hurricane, long range model guidance is indicating that Matthew could re-curve. Such a path would bring Matthew repeatedly over the near record warm waters of the Gulf Stream and possibly produce a second landfall in Florida by Wednesday of next week. Image source:The National Hurricane Center.)

Matthew — A Record-Breaking Storm in a Record Hot World

This powerful hurricane has consistently fed on sea surface temperatures in the range of 29 to 30 degrees Celsius (84 to 86 Fahrenheit). These waters are 1-3 degrees Celsius above 20th Century averages and are at or near record hot levels. Furthermore, added heat at the ocean surface has led to greater evaporation which has contributed to 75 percent relative humidity readings at the middle levels of the atmosphere.

Such high levels of heat and atmospheric moisture are not normal. They provide an excessive amount of fuel for powering intense hurricanes like Matthew. And all this heat and moisture is now made more readily available by a record hot global environment resulting from the ever-rising levels of greenhouse gasses in the Earth’s atmosphere due to fossil fuel burning.
Maintaining Major Hurricane Intensity Despite Making Landfall Twice

Yesterday this heat-fueled storm vented its fury first on Haiti and then on Cuba. But as the rains fell at rates of up to 5 inches per hour and as the winds howled in at 145 mph, the mountainous terrain of these two islands took its toll on Matthew’s circulation. According to Dr. Jeff Masters, Matthew’s eye wall was disrupted and partially collapsed as the storm tracked over rugged eastern Cuba. As a result, its peak intensity dropped off from 145 mph early Tuesday to around 115 mph or a minimal category 3 storm during the morning on Wednesday.

(Near record warm surface waters in the Caribbean Sea and in the Atlantic Ocean off the US East Coast in the range of 1-3 degrees Celsius above average combined with very high atmospheric moisture levels to fuel Matthew’s unprecedented intensity. Such conditions are consistent with those produced by human-caused climate change. Factors that provide more energy for storms to feed on when they do form. Note that the readings depicted in the map are departures from average — with red through orange, yellow and white representing above-normal temperatures. Image source: Earth Nullschool.)

Matthew Restrengthening

But Matthew has since re-emerged as a major hurricane over very warm waters near the Bahamas and it is again drawing on a nearly unprecedented supply of ocean heat and atmospheric moisture. As a result, the storm is rapidly re-strengthening. Thunderstorms around the center are rising again to towering heights. Pressures are dropping and peak wind speeds are starting to pick up. By tomorrow morning, it’s entirely possible that Matthew will have returned to Category 4 status — boasting a very large circulation and sustained winds in excess of 130 mph as it starts to threaten the Florida coast.
As of 5 PM EST on Wednesday the storm had already regained some intensity — hitting 120 mph maximum sustained winds. Model guidance puts the storm near or over the Coast of Central and Northern Florida by Friday morning with some models (ECMWF) showing a minimum central pressure near 940 to 945 mb by that time — representing a very powerful storm with winds possibly again exceeding 145 mph.
(Rapid bombification? Matthew re-intensifies as it tracks toward the Bahamas and Florida. Very dangerous situation emerging with swift, significant increases in strength possible. Image source: the National Hurricane Center.)

Matthew’s Predicted Track Could Bring Major Hurricane Conditions to Numerous East Coast Communities

Matthew is predicted to run parallel to the coast, with part of its circulation remaining over water. As a result, the storm could maintain intensity even as it drives hurricane force winds and strong storm surges into multiple cities and towns along the coast.
The subtropical ridge over the western Atlantic is still strong, and the flow pattern around this ridge should continue to steer the hurricane toward the northwest during the next day or two with no significant change in forward speed. After that time, the ridge will shift eastward, allowing Matthew to move northward very near or over the north Florida east coast, and then near or to the east of the Georgia and South Carolina coasts.
Such a path would tend to keep Matthew strong for a longer period of time. In addition, movement along the coastline could result in severe impacts ranging over a very large region — not just focusing on a particular section of the shore, but running along the oceanfront for hundreds of miles. In the worst case scenario for Matthew, diverse regions from Cape Canaveral to Jacksonville to Savannah all experience significant hurricane impacts including major hurricane winds and severe storm surge flooding.

(Hurricane Matthew has the potential to put multiple communities from Florida through Georgia under severe storm surge flooding. The above map shows a worst case scenario (1 in 10 probability) where most of St. Augustine, FL — a city of about 120,000 people — is under 1-9 feet of water. This potential is repeated in the NHS model on up and down the Florida and Georgia coastlines. Image source: The National Hurricane Center.)

Matthew Could Hit Florida Twice

But if the current forecast isn’t rough enough, the long range looks even worse. Model guidance is now starting to form a consensus that Matthew may not immediately head out to sea following its first encounter with the US East Coast. In fact, models like GFS, ECMWF and CMC are indicating that Matthew may loop back, possibly even striking Florida a second time by Wednesday (GFS). Though highly uncertain, the possibility of Matthew returning to the warm water environment that so greatly added to its strength initially, before hitting Florida a second time, was enough to draw some pretty strong words from experts like Dr. Jeff Masters over at Weather Underground earlier today.

Dr. Masters noted:
Thanks to my advancing years and a low-stress lifestyle that features daily meditation, there’s not much that can move me to profanity—except the occasional low-skill driver who endangers my life on the road. But this morning while looking at the latest weather model runs, multiple very bad words escaped my lips. I’ve been a meteorologist for 35 years, and am not easily startled by a fresh set of model results: situations in 2005 and 1992 are the only ones that come to mind. However, this morning’s depiction by our top models—the GFS, European, and UKMET—of Matthew missing getting picked up by the trough to its north this weekend and looping back to potentially punish The Bahamas and Florida next week was worthy of profuse profanity.
Such a loop back and second hit to Florida and the Bahamas is highly uncertain at this time. However, given all the heat and moisture available, there’s a possibility that Matthew could re-strengthen along such a path after the significant wind shear predicted Sunday and Monday subsides — bringing forward the possibility, however unlikely, of the same storm striking Florida and the Bahamas twice as a major hurricane over the course of 5-7 days.

It would be a very odd and unfortunate event if it did happen. One that would have been fueled by all the climate change related hot water and near record moisture readings sitting at the ocean surface and rising on up into the middle levels of the atmosphere. But given the storm now blowing up over the Bahamas this evening, a possible first strike is already looking rough enough.

Note: This is a potentially highly dangerous developing weather situation. Coastal interests from the Bahamas through Florida, Georgia and the Carolinas should stay abreast of forecasts provided by the National Hurricane Center and stay tuned to local weather statements and/or possible evacuation/emergency storm shelter information.

Scientific Hat tip to Dr. Jeff Masters
Hat tip to Colorado Bob
Hat tip to DT Lange

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