Matt Lanza

Erin putting itself together Thursday and should pass north of the islands this weekend

In brief: Tropical Storm Erin will pass north of the islands this weekend before likely beginning to turn north off the East Coast. Questions on the exact track remain that could influence impacts in various spots, so continued monitoring is recommended for the East Coast, Atlantic Canada, Bermuda, the Bahamas, and the northeast Caribbean. Invest 98L in the Gulf will probably produce mostly positive rainfall over South Texas tomorrow and Saturday.

Tropical Storm Erin

If we look at satellite this morning, it’s certainly the healthiest look Erin has had this week.

Erin looks like an actual tropical storm this morning. (Tropical Tidbits)

It’s clearly not the healthiest storm we’ve ever seen, but it’s doing enough to give the impression of slow intensification. As a result, Erin’s intensity is nudged up to 60 mph as of the 11 AM AST advisory. Using the latest map from Tomer Burg’s excellent site, it’s actually instructive to see what Erin has ahead of itself.

(Tomer Burg)

Erin is moving into an environment with very warm water temperatures, and it’s not going to exit that environment for at least 5 or 6 days. Erin should begin to tap into this environment over the next couple days, and it’s possible that we see a burst of rapid intensification at some point. Erin has not completely rid itself of dry air yet, so that may limit just how out of hand intensification can get. Whatever the case, given a favorable upper environment and warm water temps, one would expect Erin to start tapping the accelerator a bit today and tomorrow. After Friday and into this weekend, the storm may begin to “feel” some added wind shear to the west. This could slow the intensification rate a good bit. The models love this storm, and they’re quite aggressive with intensification over the next 3 to 4 days, with most pinning Erin at Cat 3 or above.

In terms of how close it gets to the islands, which is the first hurdle in terms of Erin’s track, there is strong agreement that it will pass comfortably north to avoid serious direct impacts. The Euro ensemble below shows this well.

The Euro ensemble’s 50+ members show Erin staying comfortably north of the islands, keeping serious direct impacts out of those areas. (Weathernerds.org)

What can we expect? Probably just a graze. As Erin passes north, it’s likely that some outer bands will graze Puerto Rico, the Virgin Islands, and the northeast Leeward Islands. Below is a forecast map for Saturday morning from the European operational model. Often, we tell you to ignore operational model guidance, but 2 to 3 days out, these deterministic models have value, particularly with established storms like Erin.

Erin’s Saturday morning forecast north of the Caribbean islands. (Pivotal Weather)

Mostly, however, the impacts will be marine-driven: Rough seas, high tides, rip currents.

(NWS San Juan)

Certainly something to monitor and keep track of, particularly if you have any marine interests or will be visiting the area this weekend. But this is mostly from a safety and awareness standpoint. No direct or major impacts are expected.

Beyond the Caribbean islands, what happens next? Well, there’s always some inherent uncertainty in tropical systems, but it’s not always equal. In other words, some 5 to 7 days forecasts have higher confidence than others. In this one, there is fairly high confidence that Erin is what we thought it was. Erin will turn northwest, then likely north and northeast rather quickly off the East Coast.

Erin’s forecast track has inherent uncertainty, but it is still expected to remain offshore of the East Coast. (Tropical Tidbits)

The questions I still have involve how close to the Bahamas and eventually Bermuda Erin gets. Additionally, how far offshore the storm will pass from the East Coast and Atlantic Canada. There has certainly been some “creep” to the west in the last couple days, which has undoubtedly made some folks on the East Coast a little uneasy. But at this point, all we can say is to keep an eye on things. We do not expect a track, plowing Erin into the Carolinas or New England. But it could always pass close enough for some impacts. We’ll keep you posted. Bermuda needs to watch Erin very closely. Hopefully we see some clarity on that in the next couple days.

One thing we can say for sure? Rough surf and rip currents will begin to increase by later this weekend or early next week on the East Coast. Please use caution in the water, particularly if you’re taking a late summer vacation next week.

We’ll keep you posted through the weekend.

Invest 98L

Meanwhile, in the Bay of Campeche, the tropical wave that we started watching a little more closely on Tuesday evening has now been designated Invest 98L. It actually looks okay this morning, though it lacks any sort of defined circulation center. So at this point, it’s just a coherent area of thunderstorms.

Invest 98L is well defined with thunderstorms, but it lacks any formal tropical organization. (Tropical Tidbits)

Invest 98L is going to track almost straight northwest over the next 24 to 30 hours. This should come ashore in Texas by Friday evening. Any development will be lower-end and rather disjointed. In other words, we could see a sloppy tropical depression come out of this, but we probably won’t see a named storm.

Invest 98L will move into Texas tomorrow evening. (Tropical Tidbits)

That said, given the thunderstorm organization here, we could see some locally heavy rainfall in South Texas as this comes in. I think as we saw last month, it does not take a well organized tropical system to cause problems in Texas. As this moves from the coastal bend into interior Texas, we will keep an eye on flooding risks that may emerge from this, although right now those risks are on the low to very low side.

5-day rainfall forecast focused over Texas shows generally 0.5 to 1 inch of rain on the coast, with lower amounts inland.

Overall, the thinking is that this will be more beneficial with increased rain chances over drier South Texas than anything else.

Elsewhere, no other specific waves are of serious concern right now, but we’ll keep an eye on that over the next few days and see if new areas of interest are introduced. We’ll stop there for now. Keep tabs on our Notes for any intermittent updates.

Tropical Storm Erin chugging westward, but struggling to maintain thunderstorms this morning

In brief: Tropical Storm Erin is struggling this morning due to dry air, which may impact its track some over the next 3 to 4 days. While Erin should still eventually turn out to sea, folks in the northeast Caribbean will want to monitor the storm’s progress closely this week, and those on the East Coast should continue to just keep tabs on any further changes for the time being.

Tropical Storm Erin

This morning, Erin has pressed pause on intensification as a lot of the deeper thunderstorms surrounding the storm seem to have faded away. We figured Erin would struggle a little in the first couple days, but this is a fairly substantial drop off in storm activity.

Erin’s thunderstorms have weakened, though it still has a well defined circulation. (Weathernerds.org)

One reason for the diminished look of Erin this morning is likely a healthy amount of dry air that sits in the mid-levels of the atmosphere around the northern and western flank of the storm.

Erin is battling dry air right now. (Tropical Tidbits)

Hurricanes and tropical storms need warm water, low wind shear, and moisture to thrive. Absent one of those ingredients and you probably get a sloppy outcome. Indeed, this is where we are right now.

So, what does this mean going forward? Well, if you look at Erin’s forecast track from the NHC today, it has indeed shifted a bit farther south.

(NOAA NHC)

It hasn’t shifted dramatically so, but it has shifted enough to be noticeable. This is likely because Erin’s intensification timeline has slowed down a little. Less intense storms will track a little farther south and be less apt to turn poleward (north) quickly. One of the challenges in determining the forecast track of Erin over the next several days will end up being how much dry air it has to fight off. If you look at the envelope of track possibilities through Friday evening, at least based on the European and GFS ensembles, you do see a somewhat healthy spread in possibilities opening up. Since yesterday, this has shifted a couple hundred miles south

A comparison of Monday vs Tuesday morning’s ensemble guidance on Erin shows a slight southward drift in forecast track. (Tomer Burg)

This is not a dramatic change, but when you do the virtual math here, there has definitely been a trend toward a slightly weaker system, slightly farther south. Also notice a slight bend to the west-southwest that shows up on those maps as Erin tracks west of about 55°W longitude. It’s a minor difference, but for the islands, it could have some implications.

So what does this mean going forward? Well, in the near-term it doesn’t mean much of anything. Erin will probably continue to struggle a bit until it can insulate itself from the dry air that surrounds it or shake it off entirely. This could mean that we see an additional trend to the south of Erin’s track today, perhaps getting a bit closer than some would like to the islands. On the flip side, if Erin struggles more, it would be less likely to approach the islands as a hurricane. So you have to balance the bad with the good.

Still, once it nears the islands, the overall environment is expected to improve, allowing for Erin to intensify, turn north, and scoot out to sea, though Bermuda bears close watching of course in that scenario. All that said, I think there’s at least some evidence today that while the environment around Erin is expected to improve and allow for strengthening, that doesn’t necessarily mean it will. So folks in the northeast Leeward Islands, Virgin Islands, and Puerto Rico should continue to monitor Erin’s progress closely over the coming days.

For folks on the East Coast? Generally speaking, nothing has changed with respect to the risk profile there. Erin is still expected to turn out to sea, as the break in ridging over the Atlantic persists. As soon as Erin begins to intensify, it should begin to gain latitude and eventually turn back northeast. That turn looks a little more like a J-turn today than a U-turn, but the end result would be the same. All that said, the subtle changes we’ve seen since yesterday are a good reminder to never take a hurricane forecast as a given 7 to 10 days out. Continue to monitor Erin’s progress in the coming days.

Tropical Storm Erin forms, and the forecast remains mostly the same

In brief: Tropical Storm Erin formed this morning from Invest 97L. It’s expected to make its way north of the islands by the weekend. From there, it’s likely heading out to sea, but we explain why the chance isn’t quite 100 percent. Plus, a quick update on the Gulf, which won’t see development but could see locally heavy rain this week.

Tropical Storm Erin

With our first real significant Atlantic storm of the season now likely getting underway, we’re doing a quick evening post here to just set the landscape up, as I know some people may be a little confused or wondering if things have changed since this morning’s update. In short, they haven’t changed a whole lot.

Tropical Storm Erin is currently expected to stay north of the islands. (NOAA NHC)

Erin has been identified with 45 mph maximum sustained winds just west of the Cabo Verde Islands. It’s hauling westward at over 20 mph. This quick forward speed probably won’t do it many favors over the next day or two, allowing for only gradual intensification, but it should be a slow, steady intensification over the next several days with probably a burst of rapid intensification at some point later this week or weekend. In fact, the intensity forecast for Erin is pretty dang aggressive over the next several days, showing the storm becoming a category 2 to 4 hurricane by the time we get to Friday or Saturday.

Erin will likely gain intensity rather quickly after midweek. (Tropical Tidbits)

The track forecast is in equally decent model agreement, showing a good, tight track consensus through Sunday or Monday, bringing the storm north of the Caribbean islands.

The track forecast for Erin is in strong agreement through the end of the week and probably the weekend too. (Tropical Tidbits)

Thus, the confidence in the NHC forecast shown above should be moderate to higher than usual.

For the Caribbean islands, this is unlikely to impact directly, but folks in Puerto Rico or the Virgin Islands through Anguilla or Barbuda should probably keep tabs on the size of Erin in case fringe impacts are felt in those areas.

After the weekend, Erin’s forecast confidence drops off significantly, as you’d expect from any tropical system in the day 8 to 10 timeframe. But here are a couple thoughts. First, Erin’s quick intensification will likely help it turn more northerly in time. In fact, you can see on the model track forecast spread above a very sharp northwest or even due north turn showing up on days 6 or 7. A stronger Erin would be more apt to feel the weakness in ridging that develops over the western Atlantic late this weekend and early next week. This will more than likely allow it to begin gaining latitude.

The second thing we can say is that history favors an out to sea track, though not at 100 percent. Of the 56 known named storms track within 120 nautical miles of Erin’s forecast position in 24 hours, 51 of them have gone out to sea, a U.S. hit rate of about 9 percent. Of course, Bermuda is on the way out to sea, and that was at least threatened by 7 of these storms as well.

Storms that have historically tracked within 120 nautical miles of Erin’s forecast position tomorrow evening mostly turn out to sea. (NOAA)

So currently modeling, history, and the overall setup we see favors Erin turning out to sea eventually. That said, anytime the storm is 7 to 10 days away from somewhere, you keep an eye on things. But hopefully this allows some folks to breathe a little easier in the meantime.

Gulf blob

Alright, I neglected to really touch on this earlier today, but the Gulf is looking pretty revved up right now. Usually, when you see this, you worry a bit in August. But!

The Gulf is quite busy, but no development is expected. (Weathernerds.org)

There’s a mountain of wind shear in the western Gulf right now, and the eastern Gulf isn’t exactly hospitable right now either. This is just your basic, run of the mill surface trough interacting with warm water and hot, humid Gulf weather, producing lots of thunderstorms, mostly over open water right now.

Rainfall over the next few days could be 1 to 3 inches or more in spots for parts of the Gulf Coast as this trough lifts into and through the Southeast. (Pivotal Weather)

We could see 1 to 3 inches of rain in spots, with isolated higher amounts in excess of 5 inches possible through Wednesday or Thursday as this system lifts into and across the Southeast. More tomorrow!

Invest 97L likely to develop soon but not an urgent concern for land

In brief: Invest 97L should become a tropical depression soon. While there is still plenty of uncertainty in the future, odds still currently favor a system heading out to sea ultimately. We explain more below. The rest of the tropics are ho hum for now. Strong heat in the West will gradually migrate back eastward this week, and we have details on that too.

Invest 97L on the cusp of developing

Our tropical disturbance in the eastern Atlantic is looking relatively healthy this morning, and it’s sitting just north of 15°N latitude. Development odds are up to 90 percent, and it’s entirely possible that we have a tropical depression here before this evening.

Invest 97L may be on the fringe of becoming a depression soon. (Weathernerds.org)

In a bit of an odd twist, weather modeling is actually in really, really good agreement on the general track of Invest 97L over the next 48 to 72 hours. Often in these nascent systems, there is uncertainty around exact location and placement and to some extent track. But in this case, the modeling all seems to be sniffing from the same bowl of food. In fact, you can see that European ensemble and experimental/operational AI ensemble members are all mostly packed together by Wednesday evening east of the islands.

Strong model agreement through 60 to 72 hours. (Google Weather Lab)

From there, the system will continue to track west or west-northwest across the basin arriving probably just northeast of the Leeward and Virgin Islands by late Friday or Saturday. A couple things have sort of changed since yesterday when looking at the upper-level weather pattern around whatever 97L is by Saturday or Sunday.

First, the weakness between high pressure over the Gulf and high pressure over Africa seems to have strengthened a little. This should allow 97L, likely a named storm by the weekend to gain more latitude just northeast of the islands. Historically, most storms end up tracking out to sea from there, perhaps threatening Bermuda on the way. And in this case, that’s still probably the likeliest outcome. However, there is still enough uncertainty around exactly how features orient and what intensity the storm itself has at that point that does keep the Bahamas, East Coast, and Atlantic Canada still in play here.

Invest 97L is likely a tropical storm or stronger this weekend. History suggests it will head out to sea, but there remains enough uncertainty on specifics for others to continue to monitor. (Tropical Tidbits)

But, I will say that at this time at least, the vast majority of ensemble model guidance from both AI and traditional modeling is sweeping this thing out to sea. As always, we will continue to watch and keep you posted on any changes, updates, etc.

Behind Invest 97L

There’s not a whole heck of a lot doing with any specificity right now behind 97L. There is another wave trailing it that may have some chance to develop a little farther south than 97L, but at this time, the AI modeling is most excited by this rather than the traditional ensembles. Some of the newer AI ensemble modeling has proven to be quite overzealous with tropical genesis this season, meaning anytime there’s a remote chance of development, they jump on it too quickly. For now, we’ll see if that next wave does anything, but there are no other urgent or specific concerns we’ve got heading through early next week at this time.

West Coast sizzle will migrate east this week

Ongoing heat in the Western U.S. continues. Portland had their hottest day since last summer yesterday, topping out at 99°, and today should be even a bit hotter.

(NWS Portland)

To the south, Las Vegas hit 110° yesterday, their 3rd hottest of this summer. They’ll come close to their hottest of summer today and tomorrow as well, with highs of 109-111° expected, near records for this time of year. Expect strong heat relative to normal today in Michigan and northern Maine as well. Heading through the week, the focus of heat will gradually shift back toward Florida and the Southeast.

Thursday’s heat risk peaks over Florida with near extreme heat between Tampa and Orlando. (NOAA)

Remember the high pressure system that sort of closes off the Gulf from Invest 97L? Well, it should keep the Gulf out of play from a tropical system, but it’ll definitely make you sweat!