Another busy day, but...
And Mother Nature has also had an exceedingly busy week between fires and storms. It looks like she'll continue to be busy over the weekend and into next week. Really, someone in upper management should talk to her about taking weekends to relax. Her work will still be there next week.
Tropical Storm Laura
The good news is that the track has shifted even further to the south, which means Laura (who I thought was going to be a 'he' yesterday!) crossed into the Caribbean and the forecast now takes her across the Greater Antilles islands as a Tropical Storm...
She is currently at 17N, 63.5W, heading WNW at 18mph. Now, I don't have very good data on the track anymore, so I have in the last few years gone along with the NHC track forecast at a day out because they have the best information, but from the little I do have, it looks to me like she will continue to remain on a more southern track or possibly slow down. But I do like this track they have forecast - it is the best one for everyone. She is a weak storm now, so although it will be a little windy and quite a lot rainy, it won't be as bad as a hurricane over the islands, and the interaction with land should really knock her socks off and possibly result in her not even getting past Cuba. So... hoping they have that track all squared away now.
She is definitely just a Tropical Storm. Officially her winds are 45mph, central pressure is 1008mb, which makes her a weak one (TS range: 39-73mph). She has some convection, but it isn't very well developed yet:
She has vorticity (circulation) in the lowest section of the troposphere - here's the map from 850mb:
But you can clearly see that it doesn't align with her vorticity in the middle troposphere (at 500mb):
Which means that she still doesn't have a good vertical structure and is a bit discombobulated. The reason for this is, of course, wind shear at the mid-levels. The reason she does have quite a bit of convection, even if it is off-center, is because she is over some rather warm water - the sea surface is 29 deg C, and the upper 100-125m of the water column is over 26 deg C. What we don't want is for her to stay over water and on the southern side of Cuba because that is where the water is really warm, and the warm water is really really deep (see below)!
So, the track is still the name of the game for this one. Still, a storm is a storm, so be safe my peeps in the VIs and Puerto Rico! Keep your wellies handy!
Tropical Storm Marco
He was just named today and is a very weak Tropical Storm with winds of 40mph, central pressure of 1003mb. They have been doing a slightly better job with the track on this one than with Laura, although I am not sure his center is quite where they think it is and I think he may move slightly more to the east...
He has a lot of consistent convection because he's over water with temperatures of 30 deg C, and the upper 125 m are warmer than 26 deg C.
He's in an area where he will generate a lot of convection because of the very deep, warm water he is over - I wouldn't be too surprised if he is quite a bit stronger by the end of tomorrow. This is a map showing the depth of the water which is warmer than 26 deg C to give you an idea...
This is from NOAA/AOML. As we've seen with many other storms, when they go over deeper warm water, they tend to get stronger. Yellow is not great (e.g. Laura right now - around 100m of the upper water column is warmer than 26 deg C), orange is worst (around 125-150m), and red is right out (150 - 175m). Blue is the calmer, cooler-headed end of the spectrum. I'm just saying.
So Marco has the potential to develop some more tomorrow because he's got the water and very little wind shear until he gets to the Yucatan. Beyond that, at the moment there is some pretty decent wind shear in the Gulf of Mexico so depending on how strong he is, he may decrease in intensity, at least in the southern Gulf.
But of course, everyone is talking about both Laura and Marco going on a date next Monday/Tuesday in the Gulf. I was asked about the Fujiwara Effect today by a very intelligent reader, Matthew B., who said he'd read the wiki article on it... so I can't just copy and paste from there. ;-) Fortunately, I had a small Science Alert on the Fujiwara Effect in 2017 with Hurricane Lee and Tropical Storm Maria in the Atlantic... so I can just copy and paste from there instead! Grin.
<Science Alert!> The Fujiwara Effect (or Fujiwara Interaction) happens if we have two rotating cyclones that get close to each other (within 800-900 miles), with the western one moving slower than the eastern one. If that happens, they start to rotate around each other and around a point between the two systems. Eventually they will spiral in towards that central point and may even merge - if they don't dissipate before they get too close. This is more frequently seen in the Pacific, but once every few years it happens in the Atlantic as well. For example, in 1995, Hurricane Iris eventually absorbed the remains of Tropical Storm Karen, or in 2005, Hurricane Wilma gobbled up the remains of Tropical Storm Alpha (we had so many storms that year that we started into the greek alphabet!) <End Science Alert!>
Two storms in the Gulf of Mexico at the same time is quite rare, and if the Fujiwara Effect does happen, I think that may be a first for the Gulf. Although at the moment, even if Laura survives, it looks like she's scheduled to get into the southern Gulf on Monday night, and Marco will be approaching the northern Gulf and at that time so the chances of this happening are not too high.
I forecast a weekend of looking at tropical storm data, satellite imagery, and a bit of writing...
Toodles for now!
J.
Twitter: jyovianstorm
These remarks are just what I think/see regarding tropical storms - not the opinion of any organization I represent. If you are making an evacuation decision, please heed your local emergency management and the National Hurricane Center's official forecast and local weather service announcements. This is not an official forecast. If I "run away, run away" (Monty Python), I'll let you know.
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