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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http://raleighwx.easternuswx.com/models.html
Also Allan Huffman's Dailey Weather Page has a great synopsis of what is likley happen with 90L. Best I've seen anywhere.
http://www.examiner.com/x-4053-Raleigh-Weather-Examiner
If the true centers of these form 100 miles in ether direction, the angle project will be off by 500 miles 10 days later.
The worry over a Flordia or Gulf path is premature.
These both could go fish or Yucatan.
What he said is that it is too early to tell. Have to wait until it becomes a well formed TD before the models will get a decent handle on the potential track.
How can it become TD2? We already had TD2.
Only one model predicting it, its an outlier in my opinion. It makes it to slow.
He means the remnant low becoming TD2 again.
ECMWF is too slow
It is still an "invest" just not in the traditional sense. They are still running models and stuff on it as a "LOW"
No he is talking about the remnant low of TD 2, he expects it to regenerate itself and become TD 2 once again
That's true. Usually after they fly in to the storm, and particuarly when they fly Gulfstreems around the atmosphere surrounding it, the models will shift.
Source of this information is? And if it was illegal why would it be on a website available to the public?
I edited my post. Should be between 45-50W by Monday, depending on speed.
I'm on a really old Windows ME computer, and it uses Windows Explorer instead of Internet Explorer, and it has the description in a panel on the left, and it said it is unlawful to use it otherwise.
It has increase it's convection significantly overnight. The upper level easterlies are 10-20knots which is keeping most of the convection on the western side of the system. As it continues to move to the WNW it should find more favorable conditions. Right now I agree witht he GFDL/HWRF track they are very tightly clustered and I still want to lend some credit to the ECMWF and the GFDL and HWRF provide the fastest solution of an ECMWF like track 5 days out. Then we'll be watching to see if the ridge can keep it moving to the WNW. The GFS and UKMET are the southern most solution provided 90L gains less latitude.
Technically, any images of the Euro model that are not SLP or 500mb heights are illegal...that doesn't mean they aren't out there ;)...doesn't hurt anyone.
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