Tropical Storm Nate, which developed as a depression yesterday, made landfall in Nicaragua this morning and is moving over eastern Nicaragua and Honduras this evening. Very heavy rainfall and flash flooding has already resulted in 22 deaths in Nicaragua and Costa Rica.
Nate is progressing generally northward and will emerge over the Northwest Caribbean Sea late tonight where it will have an opportunity to reorganize. The waters over that region are running in the range of 84-86 degrees F (29-30 degrees C), more than sufficient for re-intensification. With that said, the inner core will likely be badly “gutted” by the mountainous terrain of Nicaragua and Honduras and with a second landfall possible Friday evening, time will likely be limited for more robust intensification. With that said, minimal hurricane strength is possible, with a lower chance that the storm may get stronger if it’s inner core can re-organize quickly Friday.
A Hurricane Watch and Tropical Storm Warning is in effect for much of the coastal Yucatan Peninsula. Again, the major threats will be from water…heavy rain and freshwater flooding and also modest (although still hazardous) storm surge and high wave action.
Potential Impacts for Central Gulf Coast of US-
While many details are still in need of being honed in for the Central Gulf Coast…it is highly likely a tropical storm or minimal hurricane will approach the region Saturday evening with landfall early morning Sunday. The biggest threats will be from water (flooding/surge) with wind producing damage from falling trees and power outages.
Sea surface temperatures are slightly cooler along the northern Gulf Coast north of the Loop Current (82-84 degrees F/28-29 degrees C). Still more than warm enough for intensification if the system can remain over the current (a slightly farther west track may leave it over slightly cooler waters longer).
Also, given the shear currently over the Central Gulf will relax over the next couple of days (as an area of upper-level high pressure over Texas shifts westward and weakens), Nate will have an opportunity to re-intensify over the Gulf after leaving the Yucatan Peninsula. Computer models have some variability in timing of an upper trough which will move over the US Central Plains during the day Saturday. This will ultimately influence the exact track of the center of Nate. However both deterministic and ensemble members of the various models depict a likely landfall of the center somewhere from Southeast Louisiana to coastal Mississippi/Alabama. Regardless, widespread heavy rain (particularly near and east of the center), moderate storm surge flooding and high wind conditions will be likely over the coastal areas of these states by Saturday afternoon, spreading inland Saturday night and Sunday. Tropical storm force winds (sustained 39 mph+) will likely arrive on the LA Coast Saturday evening.
Tropical cyclone watches will likely be issued for portions of Louisiana, Mississippi and Alabama late tonight or early tomorrow morning.
The Atlantic Hurricane Season is currently running above normal (1966-2010 norms in parenthesis): 14 named storms (9), 8 hurricanes (6) and 5 major hurricanes (2). In terms of Accumulated Cyclone Energy (a function of maximum sustained winds over time), 2017 ranks (as of this post) as the 6th most active season on record for the North Atlantic Basin. The average temperature of the North Atlantic Main Development region (open tropics west of Africa) exceeded 83 degrees F (~28 degrees C) for the 9th time since 2002 (had never done so in the record prior going back to 1981). The MDR is the 3rd warmest on record overall.
Violent Hurricane #Irma direct threat to #Florida Sunday. #FLwx
The following is an analysis of the situation related to the potential landfall of Hurricane Irma this weekend in the United States. Let’s take a look at things currently (as of 5 pm CDT Thursday)-
Hurricane Irma is a violent Category 5 hurricane with maximum sustained winds at 175 mph (150 knots). Numerical models have been struggling on the exact path of the hurricane, but the general scenario is clear; there appears to be high confidence that the hurricane will make landfall in South Florida early-Sunday morning. The National Hurricane Center has the hurricane intensity forecast as a high-end Category 4 hurricane near landfall (max winds 150-155 mph with gusts up to 180-190 mph). This is after the hurricane impacts the southern Bahamas and the north Coast of Cuba with hurricane-force winds Friday-Saturday. After landfall either near or just north or south of Miami (this has been fluctuating in forecasts), the system is expected to advance northward spreading destructive winds, heavy rain, and (along the coast) damaging surf/surge northward up the Peninsula of Florida.
I will not sugar coat this. This is most one of the most serious hurricanes Florida has faced in a very long time. Certainly since Charley in 2004 (Category 4) and perhaps since Andrew in 1992 (Category 5). Enhanced locally by issues such as sea-level rise (climate change) and especially land use changes and urban population growth and land cover changes (geographic changes). In addition sea-surface temperatures (SSTs) were the 3rd highest on record globally for the month of August behind 2016 and 2015 (extraordinary considering no El-Nino in the tropical Pacific…much of the Atlantic basin is running above normal; in the long term trend, SSTs are warming because of climate change, however, shorter term climate variability, including the continued shorter multi-decadal cycle for enhanced SSTs and hurricane activity in the Atlantic contributing). The enhanced SSTs and deep warm waters (oceanic heat content) are leading to Irma having ample fuel to remain extremely powerful for a very long period of time. In fact, it became the longest tropical cyclone ever observed in the satellite era (since 1966) to have a strength of 160 knots (185 mph for 37 hrs straight). It has been a category 5 storm operationally since 8 am EDT Tuesday Sept 5th (now third longest streak on record in the Atlantic Basin as of this post, being out 2004 Hurricane Ivan). All this is from warm SSTs, low wind shear not sufficient to disrupt the circulation and low land interaction with the terrain of Hispaniola, which it managed to largely avoid last night (minus minor inflow of drier air off the mountainous terrain to south of the eye, lowering its intensity slightly).
A HURRICANE WATCH has been issued for much of the coastal areas, including the Keys and Lake Okeechobee (see NHC advisories for updates). Hurricane warnings will likely be issued by tomorrow night as the hurricane continues to approach. Evacuations have been called for portions of the Keys and for Miami-Dade County and other areas. If you are in South Florida and in an evacuation area for storm surge and haven’t evacuated, I would highly suggest you do so or call 311 for aid if you are disabled and have difficulty leaving your home. Surge in portions of South Florida from this hurricane could reach 10 ft or more. This is simply not survivable if you’re along the open ocean coast. It is twice as high as my height (I am 5′ 6″ tall). Surge is dependent upon the track and strength of the storm as well as the tidal heights…and if you stay, you basically put your life in the hands of a lifeless beast…
In addition, I do have serious concern Irma could make landfall in South Florida stronger than forecast. The system currently has much going for it. Thus far, the hurricane has exhibited INCREDIBLE resilience. It’s been unable to be significantly impacted by outside forces (weak vertical wind shear which would hamper weaker systems) or internal fluctuations in the inner core region surrounding the eye where the strongest winds are located. This is why Irma has remain so powerful for so long. In addition, beginning basically tonight into tomorrow, it will be entering a region of increasing sea surface temperatures and oceanic heat content (increasing heat with greater depth) and at the same time, the relatively modest vertical wind shear which has attempted to disrupt (largely unsuccessfully) the “inertially stable” inner core will remain modest or even weaken. This means, unless the system moves farther west than forecast and hits Cuba (which would be a catastrophe for them) before turning north, it would will likely (in my opinion) be a Category 5 hurricane as it approaches South Florida last Saturday night-early Sunday. So at least 160 mph sustained with gusts perhaps over 175 mph within the inner eyewall. The surge would be higher than currently forecast and as a result more lethal along the coast, extending farther inland. The winds would also be more destructive at landfall and with greater extent farther inland.
With that said, regardless, of Category 4 or 5, the south-to-north track up the peninsula as a violent hurricane moving at a relative speedy clip (over 15 mph) is a worst-case scenario at it exposes many significant populations to hurricane-force high wind event. A category 4 hurricane at landfall is a catastrophic storm for all hazards as well. Obviously if you are inland and far from the potential surge areas, be ready for days of outages with the necessary supplies and gas (which is quickly running low in many areas!).
If you are in parts of Georgia and South Carolina…keep track of Irma’s track…while there was some talk of it actually making its first landfall in those states, it appears the Florida chances of first landfall are increasing. However, damaging wind gusts (as well as very heavy rain and inland flooding) associated with the landfalling hurricane may spread northward into these states Sunday night-Monday. Track the latest forecasts and be ready for deteriorating weather conditions by the end of the weekend.
I will continue to have frequent updates on things on Twitter and Facebook. I’ll see about more extensive updates on the blog in the coming few days. Hopefully all this writing is wrong and this system misses Florida completely. There has already been incredible damage in Barbuda, Anguilla, the British Virgin Islands, as well as extensive impacts in the US Virgin Islands and Puerto Rico. The Turks and Caicos Island are suffering a direct hit this afternoon/evening. A truly awful storm we can all hope comes to a conclusion soon. But unfortunately the US may be the last on the list of targets folks in the path must be prepared to action to protect life and property.
–Meteorologist Nick Humphrey
EDIT at 7:50 pm CDT: Excuse the typo in the shear analysis graphic. That should say “Hurricane Irma”.
If you’re in South Florida or the Florida Keys…you need to know what you’ll to once watches and warnings are issued BEFORE they are issued. I do have enough confidence in the path of Hurricane Irma to state that Florida is in a very serious situation based on forecast data and so folks need to 1) track the forecast 2) know your plan, especially if you live in coastal evacuation zones 3) have emergency supplies ready. This storm already has the potential to be devastating for many people all week as it buzzsaws its way through the northern Leeward Islands, close approach to US and British Virgin Islands, then the US territory of Puerto Rico with 3.5 million people, the Dominican Republic, then portions of the Bahamas, before a close passage of the coast of Cuba. And it could do this as a large Category 4-5 hurricane.
Get ready, be ready to act if/when watches/warnings are issued and keep track of the latest forecast. Also, hope the best for our friends facing Irma right now.
I’ll updates on Irma throughout the week and you can follow me on Facebook and Twitter.
EDIT AT 10:20 am CDT: Winds in Hurricane Irma increased to 180 mph, making it the most powerful hurricane (by wind) ever observed in the North Atlantic outside the Gulf of Mexico and Caribbean Sea.
It’s August and with that it’s time for the North Atlantic to show its tropical cyclone “muscle”. Tropical waves become more numerous as mesoscale convective systems form over the tropics of West Africa and race off into the open Atlantic; their mid-level “vorticity” or spin the seed for possible further development. The National Hurricane Center in Miami has pegged one Thursday with an 80% chance of development between now and Tuesday (40% chance between now and Saturday).
Mid-range models suggest the system will develop possibly into a depression or tropical storm, moving generally westward toward the Lesser Antilles heading toward Tuesday. Much more on what will happen will depend on the system’s development. Mid-level dry air brought in from the Sahara Desert will be an issue for this system as it approaches the Lesser Antilles if it moves north of 15N. As far as upper-level winds, forecast shows a modestly favorable environment for development, but details will wait until down the road. Water temperatures in this part of the Atlantic – known as the Main Development Region (MDR) – are running up to 1.5 C (~3 F) above average with abundant warm sea surface temperatures above 26 C (79 F) west of 35 W.
Because of the strong semi-permanent “Bermuda High” expected to dominate the Central and Western Atlantic next week, this system will need to be watched by interests in the Western Atlantic Basin for potential impacts in case it does not curve northeastward out to sea because of the subtropical high pressure system to its north (assuming it develops).
Also of interest is a system in the Eastern Caribbean Sea. It is in a more hostile environment (shear and dry air main problems) and only has a 40% chance of development over the next 5 days.
The Atlantic has been running about a month ahead of schedule on named storms, but has been dead quiet on hurricanes. The 1966-2009 average for the first hurricane in the basin is coming up (August 10th), but given recent years of activity, the Accumulated Cyclone Energy (ACE) thru Aug. 2nd is running at its lowest level in the basin since 2009. But still 90% of the ACE on average occurs from here on out, so much can still happen, especially given the lack of one otherwise major hindering presence in El-Nino.
I’ll keep track of these disturbances in the coming days and have more for you if they develop into organized systems. Stay tuned!