Disturbance 90L close to tropical depression strength; TD 2 may rise again
A strong tropical wave (90L), with a large circulation and a moderate amount of heavy thunderstorm activity, is a few hundred miles southwest of the Cape Verdes Islands, off the coast of Africa. This morning's QuikSCAT pass shows that 90L has a large circulation, but this circulation is not yet well-formed, as it is elongated along an east-west axis. Satellite imagery from the European METEOSAT satellite show that the heavy thunderstorms associated with 90L are gradually becoming better organized, with some spiral banding evident on the south side of the storm. Satellite intensity estimates from NOAA already put 90L at tropical depression strength with 30 mph winds, but the storm does not yet have a well enough formed circulation to be classified as a depression. Water vapor imagery shows that since 90L is forming several hundred miles south of the dry air of the Saharan Air Layer (SAL), the storm should not be affected by dry air and dust as much as Tropical Depression Two was. However, there is some dry air from the SAL being sucked into the circulation of 90L, and this is retarding its development.
Wind shear is moderate, about 10 - 15 knots, but is forecast to fall to the low range, 5 - 10 knots, later today. Shear is then forecast to remain low for the next five days. Sea Surface Temperatures are about 28°C, and will remain in the 27 - 28°C range the next five days. The combination of low wind shear and sufficiently warm SSTs should allow 90L to develop into a tropical depression by Saturday, and potentially reach hurricane strength by Wednesday. Most of our reliable models strengthen 90L into a hurricane by Wednesday, when the storm is expected to be near the northern Lesser Antilles Islands. One important outlier is the ECMWF model, which has 90L passing to the north of the islands, and eventually recurving out to sea east of Bermuda. The ECMWF was by far the most reliable model for forecasting hurricane tracks last year. However, all of our models are pretty unreliable going out 5 days in advance for systems that have yet to reach tropical depression strength. Once 90L becomes a tropical depression and develops a well-formed circulation, the models will have a better handle on forecasting where it will go.
Figure 1. The remnants of Tropical Depression Two (left side of image) and tropical wave 90L (right side of image).
Tropical Depression Two may come back
Tropical Depression Two died yesterday, but may rise again. Satellite loops of the remnants of the storm show that heavy thunderstorms are again attempting a comeback near the axis of what is now a tropical wave. However, dry air continues to interfere with the development of the thunderstorm activity, and moderately high wind shear of 15 - 20 knots is also inhibiting the process. Wind shear over the remnants of TD 2 is expected to remain in the moderate range, 10 - 20 knots, over the next four days. Sea Surface Temperatures (SSTs) are 27°C, but will warm to 28°C two days from now. There is plenty of dry, stable air from the Saharan Air Layer (SAL) to the north and west that will continue to cause the storm problems. The relatively cool SSTs and dry air mean that any re-development of the storm will be slow to occur. NHC has given the system a medium (30 - 50% chance) of becoming a tropical depression again by Sunday morning. Only one reliable model, the NOGAPS, is predicting regeneration of TD 2. The NOAA Hurricane Hunters are flying research missions into the remnants of TD 2 today and Saturday.
I'll have an update Saturday morning, or earlier, if significant developments occur.
Jeff Masters
Reader Comments
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Great timing...
LOL. Bravo.
Each successive run with the GFS has been flattening out the trough and also a little faster with it. This does point to more of a westerly course with 90. Placement of troughs and ridges is actually a strong point of the GFS. We're still a week away, but it seems when this trough was first advertised it was a little too amplified for August. I think a weaker trough will be the solution.
At least it doesn't look like a Cat 5.
C)
and continue with a WNW track....
Are you seriously concerned with how strong the 200 hour GFS shows the system?
Amen!
while you guys are speculating over gut feelings and unsubstantiated tracts...please note the close alignments of the models...for those that have been here for awhile....can you remember when this early into a systems cycle...when the models have been so closely aligned so soon?
been keeping track this is the 10th run the gfs shows fla innits path stay tuned
Yeap... is another possible solution in the event the trough is again depicted to be stronger.
It might be a bad girl...
What about Ivan from the same year.
It just means that today we humans are responsible. Rightnow we put alot of fuel into the air system. Though the oceans take up 50% of the emitted Co-2 - just have a look on SST records.
Well you might be on to something... :)
1. The ULL over Cuba that is helping to support the flare up from the Twave in that area.
2. Ex TD2 heading into air that is completely void of moisture other than what it can generate itself.
3. A trough digging down from the N of Ex TD2 that may increase shear over it depending on the relative speeds of the two.
While Ex TD2 has been trying to mount a comeback this morning it is still struggling with a less than ideal environment where it is and cloud tops have warmed some in the last 2 hours.
Still a wait and see with this feature.
WV Loop
I have NEVER seen the models converge like this 5+ days out.
Don't include me in that bandwagon. I favored recurvature yesterday. I go by the models and climatology.
actually...what is certain..is that at this moement..no one in the conus is in the cone
hi drake how strong does that model show ti a
Their opinion doesn't change the storms track anyway...
Nope, I want it to stay far away. I wouldn't mind a hurricane day at work though. We had one last year for Fay. I saw a couple of drops of rain and a gust of wind around 20 mph.
LOL.
That's what a lot of people have been asking lol.
Are YOU seriously concerned about WHERE the 200 hour GFS shows the system?
Maybe in 5 days from now, we will have a better idea as to the general vicinity of where the storm will be 10 days from now.
IKE was pointed straight at SoFla 4 days before expected landfall...we know how that story ended.
Before anyone mobilizes FEMA trailers, lets let another day..or 8 go by.
Indeed... the main point to take out of this is not where the storm is going to hit but how the Upper level pattern are trending... so if indeed something develop you'll get an idea where it might be heading.
I cannot say how strong that system is based on looking at the GFS. The GFS cannot adequately represent the strength of a system. Conditions look favorable and there is some hot Bahamian waters. You can only speculate.
Stay safe, Play safe, Blog safe.
Cheers
AussieStorm
Take me off that list, 3 is more than enough for me.
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