This update is based on information from the National Hurricane Center’s 5PM advisory on Hurricane Irma.
Current Situation
Hurricane Irma continues to persist as a large and powerful Category 4 storm with peak sustained winds of 155 mph. Its eye still appears somewhat ragged, suggesting that it’s still undergoing an eyewall replacement cycle. This will continue to lead to fluctuations in its strength.
Headlines
Track forecast continues to edge westward. This decreases the risk Irma poses in any direct way to Georgia and South Carolina coastal areas, though storm surge threat here is still significant.
The threat of a direct hit on Miami is decreasing. However, a track to the west of Miami would result in the South Florida region being on the more dangerous eastern side of the storm.
The risk of devastating impacts to the west coast of Florida is increasing.
Irma’s eye may be moving very close to or make landfall on the northern Cuban coast. The threat of catastrophic wind and storm surge damage to Cuba’s north shore is increasing.
Risk of damage from flooding rains and tornadoes also exists. See this 1-5 day map of possible rainfall totals:
Forecast Track
Forecast models continue to edge slightly westward on a track for Irma and as such the National Hurricane Center has also adjusted its latest forecast slightly more west.
Forecast Intensity
National Hurricane Center forecasts continue to call for Irma to make landfall somewhere in South Florida as a very dangerous and powerful Category 4 storm. Outside of possible internal fluctuations and interaction with Cuba’s high terrain, there are no other inhibiting factors on Irma maintaining Category 4 strength of even possibly intensifying. Irma is entering an area of very warm sea surface temperatures with basically no mid-level wind shear.
We’ve got a wonderful stretch of below average but sunny, fall-like weather ahead of us over the weekend. The main weather story lies far to our south as Florida braces for Hurricane Irma over this same time period. Irma has weakened a bit but is still a large and dangerous Category 4 storm capable of wreaking havoc over the entire state of Florida.
Rest of today – our weather will be dictated by an area of high pressure anchored over the Great Lakes. This will give us mostly sunny skies with a cool high in the mid-70s.
High pressure firmly in control of the weather in our part of the world. You can see Hurricane Irma making its finally approach on Florida in the lower right.
Saturday – sunny with temperatures in the low-70s as the high pressure over the Great Lakes moves east a bit.
Sunday – more of the same as Saturday with sunny skies and high temperatures in the low-70s.
Monday – slightly warmer with high temperatures creeping back into the mid-70s with some more clouds.
Hurricane Irma a Major Threat to South Florida
Current Situation
Hurricane Irma has been weakening in the last 12 hours. It’s evident the storm is undergoing an eyewall replacement cycle, where the inner eye of the storm collapses and is replaced by a larger, outer eye. During these internal cycles, max wind speeds often decrease and fluctuate before the storm consolidates a new eye. It has been downgraded to a Category 4 storm with maximum sustained winds of 150 mph.
Headlines
Landfall somewhere in South Florida over the weekend is a near certainty. Outer bands from Irma are expected to reach South Florida overnight tonight. Life-threatening storm surge inundation and damage from winds of major hurricane force (115 mph) are a near-certainty for parts of South Florida.
Since midday yesterday, forecast models have trended slight back towards a westerly solution for the forecast track of the storm. This almost eliminates the risks to Georgia and South Carolina coastal areas from a direct hit from a major hurricane. However, the risk to these areas from storm surge and strong tropical storm force/marginal hurricane force winds still exists.
There is still a chance Irma could make landfall on Cuba. This would weaken the storm ahead of subsequent landfall on Florida.
Forecast Track
As mentioned above, the best performing forecast models have shifted back to a more westerly track for Hurricane Irma.
Several different forecast models take on Irma’s track.Official National Hurricane Center forecast as of 8AM today.
Forecast Intensity
While Irma has weakened to a Category 4 storm due to an ongoing eyewall replacement cycle, it remains an extremely dangerous storm with an expanding wind field due to this cycle. Hurricane force winds extend 70 miles on each side of the eye and tropical storm force winds well beyond that. It remains possible that Irma can re-strengthen if it completes the eyewall replacement cycle before it interacts with land. Mid-level wind shear remains negligible and Irma will soon be passing over very warm seas with increasing depth. Both of these factors would suggest it maintaining Category 4 strength or possibly re-intensifying to Category 5.
Uncertainties
Any landfall on Cuba or interaction of the core of the storm with the high mountains of that island would disrupt the storm and cause weakening. This would be good news for Florida, at the expense of Cuba of course.
Should the core of the storm avoid Cuba and close off a new eye before too much time elapses, it would have the possibility of re-strengthening before landfall. A strong Category 4 or even a Category 5 storm making landfall on Florida is not out of the question.
This is one of an upcoming series of special posts dedicated to Hurricane Irma. I’m hoping these posts will keep those of you who are either in areas at risk or have friends and family there informed and prepared as this historic storm bears down on the US mainland.
Current Situation
Hurricane Irma remains an impressive Category 5 storm packing sustained wind speeds of 175 mph. It is nearing the Turks and Caicos Islands as of this time.
Headlines
The threat Irma poses to South Florida as a strong Category 4 storm continues to increase
There is a risk to the Georgia and South Carolina Coasts. This risk would increase if there’s eastward movement of the storm track, as was the case in previous track forecasts.
Major impacts are expected to the Turks and Caicos and Bahamas archipelagos
The threat to the northern coast of Cuba remains high. Hurricane watches have been upgraded to warnings.
This is a large hurricane – the larger the size of the storm, the larger the storm surge it can generate. Even if the eye of the storm misses Florida to the east, the entire state could still feel the impacts of tropical storm and hurricane force winds.
Forecast Track
Here is the National Hurricane Center’s latest official forecast with a 5-day cone of uncertainty reflecting the spread in forecast models. Models have been wavering between a more westerly and easterly track in the past 24 hours which would have big implications (see below).
Here are some actual forecast model outputs on the storm’s track.
GFS model run showing Irma very close to or making landfall on the Miami area on Sunday at 8AM
Forecast Intensity
Unless the core of the storm interacts with the high terrain of Cuba by making landfall on it, it is unlikely that Irma would weaken significantly.
Wind shear is expected to remain low at the mid-levels, which means basically zero disruption to the core of the storm. Sea surface temperatures are very warm in the Florida Straits and Bahamas. This will support the storm maintaining itself as a very powerful hurricane.
Irma is expected to approach South Florida as a dangerous Category 4 storm (sustained winds over 130 mph). Even with some interaction with Florida, Georgia and South Carolina could still expect a strong Category 2 (sustained winds > 95 mph) or a Category 3 (sustained winds > 115 mph).
Uncertainties
The critical component of forecast track uncertainty is the timing and degree of influence a mid-level trough (the dip in that solid black line in the image below) on initiating Irma to begin a turn to the north as it rounds the western periphery of the Bermuda high that has been steering it thus far. The effect of a mid-level trough is both to weaken the Bermuda high and also to exert a pull on Irma to the north.
The timing of Irma’s northward turn is significant as an earlier turn would result in a more easterly track, and a later turn would result in a more westerly track. A small deviation either way could either spare an area from a direct hit by the devastating eye of the storm or bring it right into the eye.
A track to the east that takes the center of the storm away from South Florida would result in a stronger impact on the Georgia/South Carolina coasts
A track to the west would reduce the possible dangers to Georgia and South Carolina but increase the threat to the entire Florida Peninsula. This would still result in serious impacts to South Florida.
Another factor to consider is that landfall on Cuba and any significant interaction of the core of the storm with the high mountains of Cuba would result in a weaker storm affecting Florida and other US locales
Irma’s Impacts Thus Far
Overnight into today, Hurricane Irma made landfall on several small Leeward Islands including Barbuda and Saint-Martin/Sint-Maarten. These islands took a direct hit from the eyewall of Irma, which packed sustained winds of 185 mph. This resulted in catastrophic damage to Barbuda that the prime minister described as rendering the island barely habitable. Below, you can watch some footage captured by a camera at Princess Juliana International Airport located in Sint-Maarten, the Dutch side of Saint Martin as the eyewall impacted that location.
As on Barbuda, scenes of widespread damage were to be found on Sint-Maarten as well. Here’s an infrared satellite image of Irma as its eye swallowed Anguilla and Saint-Martin/Sint-Maarten last night:
Hurricane Irma has smashed an all-time record for longest duration of winds at 185 mph in the satellite era (1970s or so onward) with these winds lasting for 36 hours. This is truly incredible considering that the strongest tropical cyclones are typically found in the Western Pacific where these storms have ample time over warm water to grow.
The unofficial end of summer does indeed bring us a last gasp of summery weather. A cold front passing through mid-week brings rain and signals a return to more fall-like conditions. Later in the week, we will see high temperatures 5°F below normal. Turning towards the tropics, the risk Irma poses to our region is diminishing, but it now appears Irma will be a threat to Florida.
Rest of today – clear, with ideal conditions for outdoor activities of all kinds. High temperatures in the low-80s.
Tuesday – highs in the low-mid 80s as warm air surges ahead of an advancing cold front. Mostly sunny with increasing clouds late in the day. Some possibility for a spot shower or thunderstorm in the afternoon.
Wednesday – thunderstorms are possible overnight Tuesday as the leading edge of the cold front advances through the area. More rain is expected to ride along the frontal boundary after it passes through, bringing periods of showers throughout the day. High temperatures will be much cooler in the mid-70s with the clouds and rain.
Thursday – mostly cloudy to start with a chance for lingering rain. High temperatures will be cool again in the low-70s.
Friday – mostly sunny skies, much improved conditions as high pressure takes hold. Cool, with high temperatures in the low-70s.
Hurricane Irma an Increasing Threat to Florida
Over the weekend, Irma has been fluctuating in strengthen as it has negotiated marginal conditions for strengthening (mostly the influence of some dry air at upper levels). The National Hurricane Center still forecasts Irma to attain Category 4 strength at some point later this week (130 mph sustained winds or higher) as it encounters more favorable conditions for strengthening, and maintain at least Category 3 strengthen (sustained winds > 115 mph) throughout the forecast period.
The track forecast for Irma has continuously shifted west and south over the weekend due to the influence of an area of high pressure over the Atlantic now, and a faster forecast for the passage of the cold front mentioned above. This frontal boundary lifting out of the East Coast at a faster rate than in prior forecasts would mean that it does not influence Irma to make a turn to the north-northwest and threaten the East Coast. This has two consequences: 1) The chance for Irma to make landfall up the East Coast is diminishing, 2) On the other hand, the risk to Florida is increasing.
This run of the GFS forecast model suggests Irma making landfall on South Florida as a powerful Category 3 hurricane in one week’s time.A “spaghetti” plot of multiple model runs of GEFS, one of the forecast models that forecasters are using to analyze Irma.
It is important to note that with a week to go before Irma nears the US mainland, there could still be room for changes to the track and intensity forecasts. The National Hurricane Center specifically cautions against drawing premature conclusions about the storm’s impact on the rest of the US, while singling out Florida as an area of concern. More updates to come as we continue to watch the development of what could be a very dangerous storm.
It will definitely feel like the end of summer this weekend as temperatures will be much below average for this time of the year. The remnants of Harvey are also likely to put a damper on weekend activities Saturday night through a decent chunk of Sunday. Labor Day Monday itself looks like a gem. In the long term, I’m keeping tabs up Hurricane Irma, which worries me with its potential to affect the East Coast.
Rest of today – cool, with a Canadian high pressure center to our north-northwest, we’ll feel a refreshing north wind that will diminish through the day. High temperatures are only forecast to hit 70ºF or so even with sunny skies, 10ºF+ below normal for this time of year.
Saturday – temperatures remain cool in the uppper-60s with an easterly onshore flow ahead of an approaching warm front associated with the remnants of Harvey. Overrunning clouds will move in before rain chances build up overnight.
Sunday – rain lingers into the day on Sunday before ending by the afternoon. Mostly cloudy with temperatures in the mid-70s as we get some warmer return flow behind the storm with high pressure setting up to our southwest.
Monday – the warming pattering continues with highs returning to around normal in the low-80s with sunny skies. This is the best day for your holiday weekend grilling, and should be excellent viewing conditions for the annual West Indian Day Parade and carnival.
Hurricane Irma – possible threat to the East Coast?
We’ve entered the peak of the hurricane season and right on the toes of Harvey we have Hurricane Irma which put on an impressive display of strengthening the last couple days wen it went from a tropical storm to Category 3 major hurricane. It’s weakened a slight bit but conditions are still favorable for it re-strengthen into a powerful Category 3 of 4 storm before making an approach on the Lesser Antilles.
What is concerning to me is the storm is forecast to take a jog to the southwest over the weekend. The further south and west this storm gets before it starts the process of curving back out to sea at a higher latitude, the greater the chance that it could impact the East Coast of the US. There is still a lot of time so things could definitely change, but it is worth noting that current forecasts favor a more southerly track, enhancing the risk to us. I’ve seen GFS model runs show the storm make direct landfall on the Mid-Atlantic and Northeast. As of this morning, the GFS backed off of this type of scenario. It does bear watching though.
Nice weather from the weekend continues today. Chance for rain on Tuesday. Temperatures remain below normal through the week except Thursday. Labor Day weekend looks to start off like autumn.
Rest of today – clouds this morning expected to dissipate somewhat. Below normal temperatures with highs in the upper-70s.
Tuesday – a disturbance off the coast of northeast Florida has the potential to develop into Tropical Storm Irma. Regardless of whether the storm successfully undergoes tropical cyclogenesis, it is still anticipated to bring us some tangible weather impacts. This would be in the form of some rain especially later in the day as it makes a transition to an extra-tropical storm.
Easterly onshore winds from this storm to our south will suppress high temperatures in the low-70s and give us a mostly cloudy day.
Wednesday – unlike Tropical Storm Harvey, the storm above will accelerate quickly out to the Atlantic, so Wednesday should turn out to be a pretty decent day with mostly sunny skies and temperatures rebounding back to the upper-70s.
Thursday – a cold front will pass through the area during the day and could trigger a few scattered thunderstorms. Warmer air ahead of the cold front should give us about average high temperatures in the low-80s.
Peak Hurricane Season
We’re on the cusp of the traditional peak of the Atlantic Hurricane season, which typically begins around late August and lasts through till late September. This period typically sees the highest oceanic surface temperatures (due to the specific heat of water being relatively high, there’s a lag in time between peak solar heating of summer and actual peak ocean temperatures), which in ups the potential for tropical cyclone development.
Not surprisingly, we’ve got Harvey still devastating the Texas coast, about to re-emerge over open water before making a second landfall later this week. We’ve also got a possible tropical cyclone off of the Southeast coast and another tropical wave moving offshore of Africa that could develop into a tropical storm as it moves west. A lot of activity to monitor, hoping that none of it comes our way!
I’ve returned from Europe (missed the eclipse though!) to a very pleasant stretch of calm weather and slightly below normal temperatures. Surface high pressure to our northwest over Ontario will continue to bring us cool, dry Canadian air that evokes a more fall-like feel.
Rest of today – just about normal temperatures with highs around 80°F, skies have cleared up nicely and we should have spectacular weather for the start of the weekend.
Saturday – high pressure remains in control, and gives us another pristine day of slightly below normal temperatures in the upper-70s but lots of sun.
Sunday – basically a clone of Saturday, high temperatures in the upper-70s, lots of sun.
Monday – more of the same with temperatures again in the upper-70s, maybe a few more clouds, but who can complain especially when you consider the next section.
Hurricane Harvey a Major Threat to the Texas Coast
It’s worth mentioning here that we have a very dangerous situation developing on the Texas coast today and over the course of the next few days with Hurricane Harvey. If you have friends or family in this area, it’s not a bad idea just to try and check in with them.
GOES 16 visible satellite image of Harvey showing impressive size, distinctive eye, decent symmetrical outflow except on the side already beginning to interact with land.
Harvey originally formed over the eastern Caribbean, dissipated approaching the Yucatan, and then redeveloped as it emerged over the Bay of Campeche. Favorable conditions have allowed Harvey to strengthen quickly into a Category 2 storm, and it’s forecast to continue strengthening to Category 3 before landfall.
This would make it the first major hurricane to make landfall on the US mainland in nearly 12 years. The biggest concern with Harvey is that most forecast models have the storm stalling out after landfall, and possibly looping back out to the Gulf and making a second landfall mid-week next week in eastern Texas, still retaining tropical storm strength. Two areas of upper-level high pressure will essentially be trapping Harvey in place.
The slowing forward motion of the storm means that tropical storm and hurricane force winds will rage for many hours. The longer the winds churn up the waters of the gulf, the bigger the life-threatening storm surge along the coast. Peak storm surge of 6-12′ is forecast. That’s without waves on top. For reference, Sandy brought a peak storm surge of 14′ to The Battery. That’s well above the first, and well into the second story of most homes. On top of that, rainfall totals measuring 2-3′ are possible, which would cause widespread inland flooding.
A hot week transitions into a weekend that will see the end of the heat and humidity for at least half of next week and maybe longer. Rain and thunderstorms dot the forecast except appropriately Sunday.
Rest of today – partly sunny with high temperatures in the mid-80s. The rain and thunderstorms this morning give way to a dry day otherwise.
Saturday – a warm front moves through overnight into the morning with a cold front following right on its heels. This will bring a period thunderstorms producing heavy rain at times. Marginally favorable atmospheric conditions could spawn a few strong storms. Clouds clear up in the afternoon and highs are expected to reach normal levels in the mid-80s.
Sunday – cooler, drier air moves in behind the cold front Saturday. High pressure builds to the south and west and moves south sending cooler Canadian air around its periphery towards us. High temperatures will be comfortable around 80°F with lots of sun.
Monday – a weak disturbance brings rain and cooler temperatures, well below average only in the mid-upper 70s.
Trouble in the Tropics?
A vigorous tropical wave has spun up off the west African coast and Cabo Verde. Storms originating from this region have historically been some of the most powerful and damaging, but that’s if they can sustain the transit across the Atlantic. The National Hurricane Center has this wave at a 50% of forming into a tropical depression or storm in 2 days, and 80% chance in 5 days. It’s worrying that it’s starting to get picked up on long-term GFS model runs taking a swipe at the US East Coast as a strong tropical cyclone, however, this far out, it’s difficult to say which one of many scenarios could play out. It does bear monitoring though.
GFS for Wednesday 8/16, with the tropical system in the picture right off the East Coast of the US.
A cool and dreary end of the week leads into a continued stretch of slightly below average temperatures for the weekend. Temperatures remain on the cool side with chances for rain to start next week before a warm up in the second half of next week. Far off in the Central Atlantic, a rare April tropical storm (Arlene) has formed.
Rest of today – rains moved through overnight and lingering showers this morning should end within the next couple hours. Cloudy with high temperatures only in the upper-50s to around 60°F.
Saturday – despite winds turning to the north with high pressure moving in from the west, temperatures should still rebound into the low-60s. Partly to mostly cloudy skies.
Sunday – mostly cloudy to overcast with temperatures hovering around 60°F.
Monday – the next chance for rain comes in along with a developing coastal low that lingers through Tuesday. Timing of this coastal storm remains somewhat uncertain, so it could end up being somewhat of a pest early next week.
Rare April Tropical Storm
We’re still 2 full months off from the official start of the 2017 Atlantic hurricane season, which makes the formation of the first named storm of the season even more of a meteorological oddity. Tropical Storm Arlene will spend its life churning up the waters of the Central Atlantic without any impacts on land. It’s still worth noting that this is only the second time since the dawn of the satellite era that a tropical storm has been detected in April.
TS Arlene is the tight circulation located at around 50° W, 40° N
This week has seen unprecedented and record breaking warmth for the middle of October, with temperatures that were more indicative of mid-June. But this weekend, we’re about to get a dose of reality as temperatures drop dramatically to below normal levels, in some cases 25ºF cooler than mid-week. We get some chances for much needed rain as well with some uncertainty due to the interaction of a possible tropical/subtropical system.
Rest of today – cloudy with a high around 70ºF. Chance of rain late in the day and into the overnight hours.
Friday – chances for rain increase throughout the day and especially in the evening and overnight hours. Interaction with a possible tropical/subtropical system complicates the forecast in terms of where the heaviest rain sets up. High temperatures in the mid-70s and mostly cloudy.
Saturday – the National Hurricane Center is monitoring an area of disturbed weather off the Bahamas that they’re giving a 50% of becoming a named tropical/subtropical system in the next few days. Regardless of whether a named storm forms, this system is expected to merge with an approaching cold front Saturday. This would give the cold front an extra shot of energy and moisture, though it would appear that the bulk of this moisture and rain falls well north of the area. Behind this cold front, the pressure gradient tightens and cold air rushes in from Canada, resulting in a blustery, though sunny, day with high temperatures struggling to hit 60ºF and a brisk northwest wind.
Sunday – winds die down, and temperatures rebound to average levels in the low-60s under mostly sunny skies.
