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93L in Eastern Atlantic Growing More Organized

By: Dr. Jeff Masters, 2:43 PM GMT on July 28, 2014

An area of disturbed weather located near 10°N, 33°W at 8 am EDT Monday, about 500 miles southwest of the Cape Verde Islands, was designated Invest 93L by NHC early Monday morning. This disturbance is a more serious threat than Tropical Depression Two of last week, and has the potential to develop into a strong tropical storm before reaching the Lesser Antilles Islands on Friday or Saturday. Visible satellite loops on Monday morning showed that the disturbance had only a modest amount of spin, but infrared satellite images showed that the system's heavy thunderstorm activity had increased significantly since Sunday. Wind shear was light, 5 - 10 knots, which should aid development. Ocean temperatures were decent for development, about 27.5°C. Water vapor satellite loops showed that the atmosphere was reasonably moist in the area, though a large area of dry air lay a few hundred miles to the north.


Figure 1. Analysis of the Saharan Air Layer (SAL) made at 8 am EDT Monday July 28, 2014 using data from the Meteosat-9 satellite. Dry, dusty air was present from the coast of Africa westwards across the tropical Atlantic, but was located well to the north of tropical disturbance 93L. Image credit: University of Wisconsin CIMSS/NOAA Hurricane Research Division.


Figure 2. MODIS true-color image of 93L from approximately 9:30 am EDT July 28, 2014, when the storm was about 500 miles southwest of the Cape Verde Islands. The disturbance was embedded in the Intertropical Convergence Zone (ITCZ), the band of heavy thunderstorms that circles the globe in the tropics. Image credit: NASA.

Forecast for 93L
The 12 UTC Monday forecast from the SHIPS model predicted that wind shear will remain low to moderate, 5 - 15 knots, for the remainder of the week, aiding development. Sea Surface Temperatures (SSTs) will cool a bit to 27°C on Tuesday and Wednesday, which will tend to slow development. Two of our three reliable models for predicting tropical cyclone genesis, the GFS and UKMET models, predicted in their 00Z Monday runs that the disturbance would develop into a tropical depression by Thursday. Several of our less reliable models, the NAVGEM and Canadian models, also predicted development. The only reliable model that did not predict development was the European model, which historically has had the highest incidence of failing to predict development when development actually occurs. The fact that two out of three of the reliable genesis models predict development bolsters the odds that development will actually occur. In their 8 am EDT Monday Tropical Weather Outlook, NHC put the 5-day odds of development at 70%, up from their 40% forecast from Sunday.

All of the models predict that the disturbance will continue due west or west-northwest at 10 - 15 mph for the next five days. The UKMET is the fastest of the models, predicting that the disturbance will arrive in the Lesser Antilles Islands on Friday evening. The GFS is slower, predicting a Saturday morning arrival in the islands. Once the disturbance crosses west of about 55°W longitude on Thursday, ocean temperatures will warm to about 28°C, which should aid development. Dry air to the north will likely interfere with development late in the week, and we will have to see if the moderate levels of wind shear forecast to occur over the tropical Atlantic will be capable of driving this dry air into the core of the system, disrupting formation. The disturbance may also have trouble disentangling itself from the Intertropical Convergence Zone (ITCZ), the band of heavy thunderstorms that circles the globe in the tropics, which lies just to the south of the disturbance. Clusters of thunderstorms in the ITCZ may compete for moisture and energy, slowing development of the disturbance.

The long-range fate of 93L remains highly uncertain, and will depend upon exactly how far south the center ends up consolidating when the storm develops. Most of the 20 members of the 06Z Monday run of the GFS ensemble model (which runs the GFS model at low resolution 20 times with slightly different initial conditions to show a range of possible outcomes) showed the disturbance missing the U.S. East Coast and recurving out to sea next week; four of the members showed 93L hitting the Southeast U.S. coast. Most of the members of the 00Z Monday run of the European ensemble model showed 93L moving into the Eastern Caribbean on a more southerly trajectory without recurving.

Jeff Masters

Hurricane

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

Reader Comments

1501. hydrus
Quoting 1438. SFLWeatherman:



that is still looking pretty good, not as much convection but still pretty close to center. I think this is a depression but I don't think they will call it at 11.
JMO, I think people need to analyze a system for what it is rather than for what it was or is going to be....
It's still quite robust....
Quoting 1475. washingtonian115:

When is Florida never not in danger during hurricane season?.Lol.What about the wave behind 93L.

The past eight years.
Quoting MAweatherboy1:

Earliest I could see classification right now would be 5AM tomorrow, and it could well be later (or maybe even never). NHC may need to lower development odds to something like 60/70 at 2PM. Lots of shear out there too, and not just in the Caribbean. It's still fairly early for CV season to be in full gear, but the struggles of such a massive, healthy wave for this time of year is further evidence that we are in for a quiet season.



I see no reason at all to lower development odds, especially considering the overall structure of 93L remains excellent. I agree that tomorrow morning will be the earliest we see classification, but this thing isn't in its death rows like the ECMWF suggests it should be (and considering the ECMWF is royally failing in the WPAC with picking up cyclones that become power typhoons, I'm struggling to give it much credence in this scenario).

1506. 62901IL
Quoting 1361. hurricanes2018:

look at all the modeles now going to hit FL or the sourth coast line and go in the GOM!! NO WAY!!

Catwing island is in its path!!!
I'm hoping Dr. Master's comment that a lot of the computer models say that 93L will miss the U.S. Here in Seaside Heights, New Jersey we are only 21 months post Sandy. The Army Corps of Engineers hasn't built our 18 1/2 feet mandated dune protection system yet. They will be set in place over the winter. My town is also building a 15-foot steel seawall. That's not ready yet. We fear the word hurricane, and we were kind of bugged out that we were in the rain bands of Hurricane Arthur a few weeks back. Having a Category Two Hurricane only a hundred or so miles off the coast was frightening to us. When we get hurricanes, they tend to come clumped together, like in the 1950's. Let's hope this year is like 1914.
Yesterday night:
"It's a closed circulation! Look at that convection! Great structure. What's the NHC thinking in not upgrading it?"

This morning:
"Not vertically stacked, dry air is choking it out, the ECMWF so far is right, it's going to go west!"

Every single time, every single year.
It's unbelievable to see that the European was right after all; undoubtedly unbelievable.

BTW, G'morning, y'all!
Quoting 1505. CybrTeddy:



I see no reason at all to lower development odds, especially considering the overall structure of 93L remains excellent. I agree that tomorrow morning will be the earliest we see classification, but this thing isn't in its death rows like the ECMWF suggests it should be (and considering the ECMWF is royally failing in the WPAC with picking up cyclones that become power typhoons, I'm struggling to give it much credence in this scenario).



I don't think it's dead either, I think it's still likely we see development, but it will be a pretty long process. It remains a vigorous wave, just lacking convection.
1511. hydrus
Quoting 1507. popartpete:

I'm hoping Dr. Master's comment that a lot of the computer models say that 93L will miss the U.S. Here in Seaside Heights, New Jersey we are only 21 months posts Sandy. The Army Corps of Engineers hasn't built our 18 1/2 feet mandated dune protection system yet. They will be set in place over the winter. My town is also building a 15-foot steel seawall. That's not ready yet. We fear the word hurricane, and we were kind of bugged out that we were in the rain bands of Hurricane Arthur a few weeks back. Having a Category Two Hurricane only a hundred or so miles off the coast was frightening to us. When we get hurricanes, they tend to come clumped together, like in the 1950's. Let's hope this year is like 1914.


The 1950s were even worse in NC: two in 54 (one being Hazel) and three in 1955, all five being retired names. Let's avoid that.
I definitely don't think it's going to fall apart or something, but if it's not flaming strong near the lesser antilles and just takes its time in organizing, we may have to watch out for a more southern path.
From Dr, M. (above); Once the disturbance crosses west of about 55°W longitude on Thursday, ocean temperatures will warm to about 28°C, which should aid development.

Regardless of what happens between today and tomorrow, the storm will reach more favorable conditions in about 48 hours; the issue at the moment is whether it will reach TD/TS before then which might be why some models are hinting a little more to the East trackwise.
Quoting wunderkidcayman:
Well well well
Why am I not surprised what I see
93L hasn't gotten better organised with convection
The models just keep, on shifting S and W I think we may continue to see this by the way
Recon expected to fly day after tomorrow
I put the center as of right now near 9.5N 39W it will be soon passing 40W
To be honest I don't mind that the convection had weakened and not really redevelop any we can see the low level structure better now
It's seems better than yesterday/last night but still needs work


There has been a slight shift to the west when looking at the GFS model, but the overall path/direction remains pretty much the same.

Yesterday at this time the GFS put 93L directly over Bermuda. Today the GFS puts 93L a couple hundred miles west of Bermuda.



If this trend were to continue, it could possibly put the outerbanks in play. I'll be interested to see what the 12z shows.
Quoting 1505. CybrTeddy:



I see no reason at all to lower development odds, especially considering the overall structure of 93L remains excellent. I agree that tomorrow morning will be the earliest we see classification, but this thing isn't in its death rows like the ECMWF suggests it should be (and considering the ECMWF is royally failing in the WPAC with picking up cyclones that become power typhoons, I'm struggling to give it much credence in this scenario).


The wave behind 93L is looking really good, might be mention at 8pm today.
Quoting 1487. MAweatherboy1:

SAL appears to be choking it from the north. It could be awhile before this is classified. Deep convection is really running out. The ECMWF is looking good right now.



Edit: Btw, the wave behind 93L looks pretty good. I'm a little surprised the NHC hasn't mentioned that one with at least a 0/20 percentage or something like that.
The Euro so far have been pretty bad. Haven't show most typhoon in the Wpac. The gfs at least show them even though it strength them too much. I believe this season might be a little more active than we thought.
1519. hydrus
Quoting 1494. K8eCane:

There is the Hebert Box, and then there is my magic ball. Its usually pretty accurate. I just got a new roof. This means that 93L will eventually make it to the mouth of the cape fear river with 100 mph winds, basically ripping up my roof .


Well at least UNCW ended summer classes, better than 40/117 traffic if this was August-October
1521. hydrus
JeffMasters has created a new entry.
Quoting 1505. CybrTeddy:



I see no reason at all to lower development odds, especially considering the overall structure of 93L remains excellent. I agree that tomorrow morning will be the earliest we see classification, but this thing isn't in its death rows like the ECMWF suggests it should be (and considering the ECMWF is royally failing in the WPAC with picking up cyclones that become power typhoons, I'm struggling to give it much credence in this scenario).



GFS has a little something from the wave behind it. Will be interesting to watch, though it wouldn't likely amount to much, it could be a quick spin up.
Q: Gro

Anybody know the speeds of 93 and the pouch behind it? Could the newest pouch speed up and engulf 93?
Quoting 1505. CybrTeddy:



I see no reason at all to lower development odds, especially considering the overall structure of 93L remains excellent. I agree that tomorrow morning will be the earliest we see classification, but this thing isn't in its death rows like the ECMWF suggests it should be (and considering the ECMWF is royally failing in the WPAC with picking up cyclones that become power typhoons, I'm struggling to give it much credence in this scenario).




tropical wave back of invest 93L looking good to
Quoting 1448. ncstorm:

wow!!!..pick a line..any line..




the pink one please...
1529. hydrus
1530. AztecCe
Quoting 1529. hydrus:



I don't like the loom of that map! I'm so tired of rain here