Matt Lanza

How did Oscar pop out of the garbage can without anyone noticing? A look back and what we’re watching next

Headlines

  • Tropical Storm Oscar will continue to dump heavy rain on parts of Cuba and the Bahamas as it exits out to sea this week.
  • We take a look at why we wrote Invest 94L off on Friday before it became Oscar, and in our Monday morning quarterbacking, we look at hints we could have missed.
  • Conditions may become favorable for further tropical development next week in the western Caribbean; we discuss who is usually still on the hook in early November.

Tropical Storm Oscar’s route to surprising us

Oscar is still lashing parts of the southwest Atlantic with heavy rain and gusty winds today. According to Michael Lowry, Oscar was indeed the smallest known Atlantic hurricane on record. He also accurately described Oscar’s development pathway as “nightmare fuel” for forecasters, and this forecaster could not agree more. Oscar went from nothingness to probably a category 2 or even 3 microstorm over the course of hours. This has happened in the Pacific as recently as this past summer with Hurricane John. To a lesser extent, we saw Otis last season defy forecasts and go ballistic to a category 5 storm. But every so often these storms serve as a reminder that modeling is imperfect, very imperfect.

Here’s an animated loop of Invest 94L’s forecast from the GFS model last Friday morning. You can see it takes 94L/Oscar to the west over the Turks and Caicos Islands north of Hispaniola but never develops the system and has it fall it apart rather quickly.

Friday morning’s GFS model failed to capture much development risk for Oscar as it came toward the Turks and Caicos Islands and Cuba. (Tropical Tidbits)

The European model from Friday morning offered a somewhat more realistic outcome, but even it did not look foreboding at the time and probably justified somewhere between a 10 and 30 percent chance of tropical development.

The European model was more aggressive but it even fell well short of what actually happened, though doing a much better job than the GFS in reality. (Tropical Tidbits)

Still, a minimum pressure of around 986 mb was reported over the weekend from Oscar, well under the minimum of about 1003 mb shown here on the Euro. Somewhat surprisingly, the European AI model did fairly well here, or at least was somewhat similar in nature to the Euro shown above. The ICON model did not do well, which marks one of its worst forecasts of the season.

I am somewhat intrigued by the European performance though. Small storms are tough to forecast, and we’ve noted in the past that model resolution has a lot to do with this. You simply cannot capture a hurricane that is basically the size of a typical thunderstorm complex. However, there remains something of an “art” to forecasting where one can paintbrush in some accents to improve on an otherwise finished canvas. This is a situation where looking at the Euro probably would give most of us some pause at least for writing something off. Perhaps that’s something I should have noticed more back on Friday. There are whispers of 2007’s Hurricane Humberto in cases like this. I think it just goes to show you never to take anything for granted in the tropics. You’re constantly humbled in this world.

Oscar is a much weaker tropical storm right now, and it is expected to head out to sea as such over the next day or two. (NOAA NHC)

Anyway, Oscar will turn back away from Cuba and head out to sea over the next day or so. But it will dump extensive rainfall over Cuba and the southeast Bahamas.

Additional rains in excess of 12 inches (300 mm) are possible over Cuba, with upwards of 6 inches (150 mm) in parts of the Bahamas as Oscar exits. (NOAA WPC)

Rains in excess of a foot (300 mm) are possible for small portions of southeast Cuba and up to 150 mm in the southeast Bahamas.

Beyond Oscar: Quiet, then what?

No additional tropical development is expected across the Atlantic for the rest of this week. Typically, we would begin talking about the season shutting down around now. While November storms do happen at times, they tend to be infrequent, and on an ACE basis, hurricane season is now 90 percent over. And after this week it will be about 93 percent over. But that said, the background state of the Atlantic appears as if it is going to get more favorable for development again just as we head toward November. Where would you expect storms to form in November?

Early November climatology favors the western Caribbean and open Atlantic. (NOAA NHC)

Typically, you’d look in the open Atlantic north and east of the Caribbean or in the Caribbean, just east of Central America. The latter area is the one to watch heading into November, as numerous ensemble members are beginning to pick up on activity there. Where it goes is TBD, but the water in that area remains very, very warm, which could more than support a significant storm for portions of the western Caribbean, perhaps including Central America. These storms typically get brushed off to the north and east relatively quickly by wind shear and cold fronts, so the western Gulf is probably off the hook. The eastern Gulf should still keep an eye on things, but the Caribbean should definitely keep tabs on anything that tries to develop next week. For now it’s just speculation and model hints. We’ll keep you posted as things clear up some closer in.

Surprise, surprise with two named storms in the Atlantic today

Headlines

  • Yesterday’s invests are today’s named storms.
  • Nadine is moving inland in Central America and Mexico, producing locally heavy rainfall.
  • Oscar is a micro hurricane north of Hispaniola bringing rough conditions to the Turks and Caicos Islands and perhaps the southeastern Bahamas and parts of Cuba.

Tropical Storm Nadine

Yesterday we noted that Invest 95L had a shot to become a depression or low-end tropical storm before moving into Central America today. That is indeed what happened, as Tropical Storm Nadine formed from the mess, and it is now moving inland.

Total rainfall from Nadine should be in excess of 12 inches (300 mm) in portions of Mexico. (NOAA WPC)

Nadine is primarily a rainmaker, and flash flooding is a good bet for portions of the Yucatan, Belize, and Veracruz and Oaxaca. No further strengthening is expected.

Hurricane Oscar

The Oscar for most surprising storm of the season goes to Oscar! Not only did we get a tropical storm out of Invest 94L, we got Hurricane Oscar.

Hurricane Oscar is a tiny, tiny storm with 80 mph winds. (Weathernerds.org)

Hurricane-force winds extend out a total of 5 miles from the center, while tropical storm force winds extend out about 45 miles. Oscar could best be described as a “microcane.” Still, those winds are bearing down on the Turks and Caicos Islands and moving toward the southeastern Bahamas. Widespread tropical storm and isolated hurricane conditions are likely with this as it passes through.

Oscar is expected to drift southwest-ward into or near Cuba by Monday before turning northeast out to sea. (NOAA NHC)

Nothing about Oscar is simple. Storms this small will periodically be big misses in the model world, underscoring the value of reconnaissance flights and other observational tools. Modeling completely whiffed on this yesterday and even up to this morning. This is another post for another day, but thankfully the forecast has been updated, and it now appears we have some solid footing on Oscar for folks in the Turks and Caicos and Bahamas, as well as in Cuba. At this point, no threat to the U.S. is seen, as wind shear is too high just west of here, something that should make Oscar grouchy early next week. Interests in Cuba and the southwest Atlantic should continue monitoring Oscar’s progress.

Invest 95L will clear the picture this weekend as a rainmaker in Central America, while Invest 94L dissipates

Headlines

  • Invest 94L just north of the Caribbean islands is going to fall prey to epic amounts of wind shear in the southwest Atlantic this weekend, ending any low-risk development potential.
  • Invest 95L has a very narrow window through Saturday morning to organize before moving across land in Central America as a rainmaker.
  • The tropics look fairly quiet heading into next week.

Thanks to Eric for covering me this week while I underwent oral surgery for orthodontia. I’ll just say it’s about as glamorous as it sounds. Thanks to Methodist Hospital here in Houston for a good procedure and great quality care afterwards.

Let’s take a dip into the tropics.

Invest 94L’s last gasp

What is left of Invest 94L is moving just north of the Lesser Antilles and Puerto Rico today. This is a rather robust area of thunderstorms, but it lacks any organization.

Invest 94L is producing widespread thunderstorms mainly north of the islands on Friday afternoon. (Weathernerds.org)

Over the next couple days, 94L will continue westward over the next 24 hours or so before it’s completely enveloped by significant wind shear that has overtaken the Gulf of Mexico and southwest Atlantic. Wind shear is as high as 90 knots right now across Florida, which is completely inhospitable for tropical development and some of the strongest shear I’ve seen here this time of year. So, thanks for the memories, Invest 94L and we wish you well.

Invest 95L to dump rain on Central America

Meanwhile, Invest 95L is in a bit of a different situation. This disturbance is located off the coasts of Belize and Honduras this afternoon. It is also showing robust thunderstorm activity.

Invest 95L has a short window to become a depression or low-end named tropical storm before moving inland over Central America tonight. (Weathernerds.org)

This one has a much less hostile environment to develop in than Invest 94L to the north does. However, it has a key limiting factor: Time. Invest 95L has about 24 hours or less left over water before it moves inland across Belize and Central America. In that time, it could become a tropical depression or low-end tropical storm, but no further development would be expected. Still, heavy rainfall is likely in Central America this weekend from Invest 95L that could cause some flooding issues. There is a chance that the remnants of 95L merge with another Pacific disturbance to form a storm next week that rides westward away from Mexico. But beyond this weekend’s rainfall, 95L is not a threat to land.

Beyond the Invests

At this point, there is nothing to speak of in the tropics once 94L and 95L exit the picture. That’ll give us a few more days of rest here. There are signs that the tropics could get active again heading into November, but it’s important to note that as the Northern Hemisphere pattern begins to shift toward winter, the typical behaviors of tropical systems don’t always continue. We’ll touch more on this next week.

In the meantime, have a good weekend, and don’t forget to check out our Sponsors page above. Thank you to them for their support of The Eyewall this hurricane season!

Invest 94L to be a fickle system in the Atlantic this week but poses minimal serious risk at this time

Headlines

  • Invest 94L is in the middle of the central Atlantic, and has about a 50/50 chance to develop as it comes west this week.
  • Any development would likely be slow to occur and modest impacts to the Caribbean are possible by the weekend.
  • We anticipate that 94L would fall prey to copious amounts of wind shear in the southwest Atlantic and Gulf before it makes it to the U.S., and it is unlikely to ever be a serious threat to the Southeast.
  • No other noteworthy developments are expected.

Invest 94L: Worth watching, but not a very serious concern

The next disturbance we have our eyes on is Invest 94L, a tropical wave moving through the Atlantic right now. The NHC is giving this about a 50/50 shot at development over the next several days.

A tropical system has about a 50/50 chance to develop in the Atlantic over the next few days. (NOAA NHC)

If you live in Florida, at first glance, your stomach may sink, but in reality it is mid-October, not mid-August. Storms generally do not form here and long track their way to the United States. Also, it’s important to note that the hatched area is not the track of a nascent system but rather the area in which the system may develop. In other words, Invest 94L may develop somewhere in that orange hatched region. If it develops.

So over the next several days, Invest 94L will come westward.

Where is Invest 94L? It’s the little area of thunderstorms in the middle of the image. (Weathernerds.org)

For now at least, 94L is located in a pretty hostile area with lots of dry air surrounding it, and a bit of shear in the vicinity too. Over the next couple days, that may back off some, and that’s when 94L could make an effort to develop slowly. If there is a point where 94L has its best chance of developing, it’s probably in about 3 days as it approaches the northern Leeward Islands and perhaps the Virgin Islands and Puerto Rico. Again, development is probably going to be sluggish here, so we aren’t expecting a Milton or Helene-esque blast of rapid intensification or anything. But if you are in the islands or planning to visit the eastern Caribbean islands this weekend, it’s something you’ll at least want to monitor. Most modeling keeps the ceiling on 94L low as it moves into the islands.

From there, it’s going to be difficult to see Invest 94L making it much farther west while remaining intact. There is a wall of wind shear forecast to be over the Gulf and Southeast this weekend which would almost certainly shred 94L or whatever it is at that point (provided Hispaniola doesn’t get to shred it first). In other words, by the time we get later into the weekend or early next week, it’s difficult to think that this one remains a major concern.

Copious wind shear should do the job on 94L/Nadine eventually. (Tropical Tidbits)

So bottom line on Invest 94L: Watch it in the Caribbean. Keep tabs on it to the west. But in general, we do not believe this one will be a major issue at this time.

Elsewhere

There’s nothing else we really have our eyes on. We are seeing some periodic signs of Caribbean development from the GFS model in particular. That seems to have very limited ensemble support or support from other models that have performed well this tropical season. At this point, the only organized system they seem to be picking up over the next 7 to 10 days is Invest 94L. So we anticipate that’ll be the only real game in town for a bit.