Tropical Storm Alex (formerly Potential Tropical Cyclone One) is passing Bermuda today, causing some wind and rain but shouldn’t be anything bad unless something breaks that shouldn’t. Alex is already losing what tropical characteristic it had, and will be absorbed into the wider north Atlantic weather by mid-week. Here is the impact swath (winds over 40mph, the point at which you start to see big tree limbs break), probably a bit exaggerated due to the disorganized nature of the storm.
Potential Tropical Cyclone One finally became organized enough for the US National Hurricane Center to declare it a Tropical Storm Alex. Alex is well offshore now, with the last few showers departing The Bahamas, and looks to pass north of Bermuda tomorrow (Monday 6 June), still as a tropical storm but more than likely already transitioning to an extra-tropical system. Here is Alex as the sun rises over the Atlantic …
PTC1/Alex was never really a traditional tropical storm, and in past years would not likely have been tracked. This presents a dilemma for those trying to figure out if hurricane climatology is changing. Better technology and changing criteria for tracking and warning means comparing 2022 with 2000, much less 1970, 1950, or 1920, is a major challenge. NOAA has been trying to do a reanalysis of the “satellite era” to try to identify tropical systems that were not in the data bases, and found 14 in the five years from 1966 to 1970. This is a major reason why you should be very careful when people say this or that weather system, or changing numbers, is due to climate change. In many cases we just don’t have the data to say. Now, that’s not an excuse to do nothing about human impacts on the environment (not to mention the many related resource and socioeconomic issues that are convoluted with this problem), but it does show it’s not simple or straightforward.
Potential Tropical Cyclone One is still an unrealized potential, and shows no signs of organization before the associated mess of rain squalls moves past Florida. Here is what it looks like on InfraRed satellite (the sun isn’t up yet as I write this):
There are actually several “centers” depending on how you define that, including the small convection-free swirl of clouds you can see in the center of the image. NHC thinks this mess will consolidate into a single center once it moves past Florida and The Bahamas, but they are off the hook for a real tropical storm. That doesn’t mean that some rain squalls with tropical storm force winds won’t pass by this morning, but more like the typical summer downpours and thunderstorms than a real tropical storm.
For being such a disorganized mess the track models and forecasts are remarkably consistent, taking it out parallel to the US Southeast coast towards Bermuda. There is still a chance that this will develop briefly in to Tropical Storm Alex before it gets there, but it will likely be short lived before conditions deteriorate and it becomes extratropical.
So far Potential Tropical Cyclone One can’t get it’s act together. It’s a very broad and disorganized system, and all of the rain and wind is displaced far to the east of the center, here from GOES East just before 5pm …
Here is the regional radar composite – Florida is getting a lot of rain already. It may well be that the rain will be ending before the storm itself actually passes over the state!
The hurricane center is still thinking PTC1 will organize enough to become Tropical Storm Alex before landfall, which should just after noon tomorrow (Saturday). The biggest “threat” from PTC1, even if it does evolve in to Tropical Storm Alex, will be heavy rain. Here’s a link to NHC’s latest Key Messages regarding Potential Tropical Cyclone One (en Español: Mensajes Claves).
Elsewhere, just off the US east coast there is an area NHC is watching, but chances of development are small, and if something does spin up it seems at worst it would give Bermuda a windy day before moving out to sea.
Potential Tropical Cyclone One is a large, disorganized system that is producing tropical storm force winds, but technically isn’t a tropical storm (more on that later). In terms of impacts, it should just be some wind and rain – here are NHC’s Key Messages regarding Potential Tropical Cyclone One. As a reminder, once a storm forms the “Key Messages” product is a nice summary of watches, warnings, and forecast. Here is my TAOS/TC impact estimate based on the 5am forecast. Bottom line is windy/rainy weekend for Cuba, south Florida and the northern islands of The Bahamas, minimal damage other than some trees down, scattered power outages, very scattered roof damage, that sort of thing. Economic impact should be transitory, under $100 million, and recovered quickly. Elsewhere the storm may cause rip currents along the Southeastern US coast next week.
So what the heck is a “Potential Tropical Cyclone”? In the past these kinds of storms were not tracked and reported by the Hurricane Center until they met the formal criteria for being a tropical storm. That would mean a distinct (from other systems) warm core, closed circulation. The problem is that in some conditions a tropical storm can form from an otherwise disorganized disturbance before the system crosses land, and less than the normal time frame when watches are issued. This became more of an issue in 2010 when the lead time for a watch was increased from 36 to 48 hours, and a warning form 24 to 36 hours, and more storms were forming withing those time frames and people were not getting as much notice. So in order to give people warning and time to prepare, NHC starts advisories as a “Potential Tropical Cyclone” on systems that are forecast to become actual tropical systems. So like a lot of things in tropical meteorology, it’s a mix of actual meteorology, administrative issues, and emergency management needs.
Here is a handy reference to terms like PTC, tropical wave, tropical storm, etc., from the NWS Mobile, AL office. And here are the “new” (as of 2010) criteria for watches and warnings.
Although still not well organized, and not in a great environment for development, the system off of Yucatan continues to move slowly northeast. Since it has a good potential to become at least a tropical depression or low end tropical storm, the hurricane center will likely start advisories and post watches later today as at least a “potential tropical cyclone.” At the moment the models aren’t terribly enthusiastic about the system, most keeping it at minimal tropical storm strength. Here is what the US GFS model shows for Saturday Morning at 8am, a disorganized minimal tropical storm …
Some of the models don’t even form a coherent system (just a broad area of disturbed weather). In the map above you can see two distinct “centers” (the “L” symbols), indicating a very disorganized system. Here is what some of the models are showing as tracks, for a disorganized mess they are actually fairly consistent …
Other than a lot of rain it’s not likely this storm will get organized enough to produce significantly damaging winds. Unless you’re just unlucky and a tree falls on your house, or something breaks that shouldn’t, this should be just a rain event for Cuba, Florida and The Bahamas. For the Southeastern US (Georgia and Florida), an approaching cold front that will bring rain Friday and early Saturday will have moved past, and the system (tropical storm or not) should stay far enough away to not cause any impacts other than perhaps waves and a risk of rip tides at the beach.
We have the first Magic Words(tm) of the Atlantic hurricane season! The latest (2pm Tuesday 31 May) NHC five day outlook shows an ominous red X and hashmark of doom pointed towards Florida …
As I frequently recommend, read the text for the graphic before getting too excited. Here’s what it says, with the “magic words” highlighted:
A large and complex area of low pressure is expected to develop near the Yucatan Peninsula and the northwestern Caribbean Sea in a couple of days, partially related to the remnants of Agatha from the eastern Pacific. Despite strong upper-level winds over the area, this system is likely to become a tropical depression while it moves northeastward over the northwestern Caribbean Sea and southeastern Gulf of Mexico late Thursday or Friday. Regardless of development, locally heavy rainfall is likely across portions of southeastern Mexico, the Yucatan Peninsula, Guatemala, and Belize during the next couple of days, spreading across western Cuba, southern Florida, and the Florida Keys on Friday and Saturday. Interests in the Yucatan Peninsula, western Cuba, the Florida Keys and the Florida Peninsula should monitor the progress of this system.
NHC’s Tropical Weather Outlooks follow a specific pattern. They tell you what the thing is (“A large and complex area of low pressure…”) then they will have the phrases Interests in <some place, in this case highlighted in red> should <do something, here in green>. So if you’re (someplace), do that thing – otherwise, don’t worry about it.
In this case the models seem to be showing, well, a large and complex area of low pressure, which are forecast to dump a lot of rain and maybe spin up some tropical winds. The latest GFS run did not form as clear of a center as it has previously, but any organization is still a couple of days away. Even if it does become a depression or minimal tropical storm, it probably won’t be a dangerous system until it is past the Bahamas as it treks northeast (and probably not then either). But we may get “Alex” out of it. As the TWO says, monitor the progress (if you’re in Florida) or enjoy the short work week (if you’re most other folks except me or another profession who works all the time on some crisis or another …).
The slowly moving Hurricane Agatha is making landfall on the west coast of Mexico this evening. Tropical storm force winds and heavy rain are already being felt on the Mexican coast, and conditions will worsen throughout the day. Here’s the latest impact forecast map using my TAOS/TC model, based on the official forecast:
Agatha is a strong Category Two hurricane at 110mph (95 kt) winds. The forecast keeps it at that intensity, although it might barely make Cat 3 status before landfall. Either way that shouldn’t change the impact estimates much. Agatha is a small storm, but there are still around 1.5 million people in the potential damage swath. The economic impact estimate has decreased a little with the track and intensity forecast changes, now at about $200 Million USD.
It is not likely Agatha will survive long after landfall, and while some of the track models do take the remnants into the Gulf on the current track the dynamics of it being a recognizable storm just aren’t there. NHC is showing an area of potential development around the Yucatan Peninsula in a couple of days (the yellow blob on the five day outlook (link)). Some of the remnant moisture of Agatha might contribute to the development of that potential system. The GFS model has been persistent in forecasting a storm to spin up off the coast of Belize in three or four days, then track across Cuba and the Bahamas as it moves northeast, ending up between Bermuda and North Carolina in about 10 days. While of interest to modelers and long range forecasters, it’s WAY too early to speculate or get excited about it.
It seems that the center of Isaias is reforming just off the north shore of the Dominican Republic. What that means in short is that it seems to have survived more intact than had it gone a bit further west, and the likely track has shifted a bit. NHC has also changed their forecast philosophy a little (Key Messages regarding Tropical Storm Isaias (en Español: Mensajes Claves)) and now forecast the storm to become a minimal hurricane – but not much more than that since conditions aren’t terribly favorable. So what does this mean? Not all that much. It makes the scenario where the storm come up mid-Florida much less likely, so the worst of the storm will stay offshore from them the Bahamas will take the brunt, but Isaias is fast moving and this is no Dorian. Nevertheless, The Bahamas should prepare for hurricane conditions for late tomorrow through Sunday. The coast of Florida is now under a tropical storm watch, and the Fort Lauderdale to Cape Canaveral area may see some stormy weather if the storm slows and turns in 48-72 hours just offshore as forecast. For GA/SC, maybe breezy, some gusty rain right on the coast, depending on the timing of the onshore winds and tides low lying areas that get water with above normal tides might see a little flooding, but this track is far enough offshore to not be much risk – IF the storm goes as planned. Consider this an opportunity to think through your hurricane plans for a real storm threat. Hatteras is more likely to get side-swiped, but they are used to this sort of thing. The Canadian Maritines might get a strong blow in aboot six days.