TD 2 nearly dead; African disturbance 90L gathering strength
Tropical Depression Two is near death, but is still worth watching. The dry, Saharan air to the north and west of the depression, combined with moderately high levels of wind shear of 15 - 20 knots, have almost completely destroyed all of TD 2's heavy thunderstorms. Satellite loops of the storm show a well-formed circulation, but almost no heavy thunderstorm activity.
Wind shear over TD 2 is expected to remain in the modereate range, 10 - 20 knots, over the next five days. Sea Surface Temperatures (SSTs) are 27°C, but will warm to 28°C three days from now. There is plenty of dry, stable air from the Saharan Air Layer (SAL) to to TD 2's north and west that will continue to cause the storm problems. The relatively cool SSTs and dry air mean that TD 2 will not be able to intensify quickly, and some of the models indicate the TD 2 may get destroyed in the next day or two. However, several models still predict TD 2 will become a tropical storm. The HWRF model predicts TD 2 will become a hurricane five days from now, but this seems unlikely given the dry air and relatively high wind shear affecting the storm.
Figure 1. Tropical Depression Two (left side of image) and tropical wave 90L (right side of image).
African tropical wave 90L
A strong tropical wave with a large circulation and plenty of heavy thunderstorm activity is a few hundred miles south of the Cape Verdes Islands, off the coast of Africa. NHC dubbed this disturbance 90L this morning. This morning's QuikSCAT pass shows that 90L has a very large circulation, and top winds of about 30 mph. Satellite imagery from the European METEOSAT satellite show that the heavy thunderstorms associated with 90L are in two major bands, to the north and to the south of the center. There is no heavy thunderstorm activity near the center yet, and this would have to happen before 90L can be named Tropical Depression Three. 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 has been. Wind shear is about 20 knots over 90L, and is forecast to remain in the moderate range, 10 - 20 knots, over the next five days. Sea Surface Temperatures are about 28°C, and will remain in the 27 - 28°C range the next five days, which are high enough above the 26°C threshold for tropical cyclone formation to allow some slow development to occur. The GFS and ECMWF models continue to predict the development of this wave, though they are now less aggressive about intensifying it than they were in earlier runs. The consensus among the reliable HWRF, GFDL, GFS, and ECMWF models is to bring 90L to point near or just north of the northernmost Lesser Antilles Islands 6 - 8 days from now. The storm could be at hurricane strength by then, as forecast by the SHIPS intensity model.
I'll have an update Friday morning.
Jeff Masters
Reader Comments
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Crown weather
Invest 90L has a good potential to eventually become a major hurricane, possibly as early as Monday. The consistency in the model guidance has been remarkable, and in addition, the low latitude track Invest 90L should take will place it in higher sea surface temperatures and not be influenced as much by the dry Saharan Air Layer.
Accuweather:
A large tropical wave just south-southeast of the Cape Verde Islands extending from 17 north and 22 west to 6 north and 19 west. This wave lost most of its convection Wednesday evening, but it still has a chance of becoming a tropical depression over the next 24 to 36 hours as upper-level conditions are favorable for development. Computer models have been picking up on this feature for several days now and strengthen it into a hurricane as it moves westward. This will have to be closely watched over the next several days as it may pass near the Lesser Antilles around the early to middle part of next week. It would likely take until the weekend of Aug. 22 to impact the United States potentially.
Hey, what's with that red line? >:(
If I wanted to roost the chickens back at home, I would holler at my dad so that he sees this, and then he'd call the neighbor, and the banter would begin...
"It's gonna cut us in half!"
Failure to evacuate will cause certain death.
LOL That's great.
I cant believe the drastic change in the blog...what a difference a few storms make.
the red line is the GFS
downcaster
Folks the ALL CLEAR has sounded. Lets all go back to being lax just like this season has been.
My check list
A. Scratch out 90L
B. Maybe watch TD2
C. Next system please
Ignore him, I've had him on my list for awhile.
The barb its from a ship a little off shore & the whole SE side of DR doesn't have any mountains anyhow... Yeah it's only 5 knots but weak west winds shows something is trying to work to the surface. Come..join us slumming buoys, ships & surface observations.
true but the decisions between life and death and tropical cyclones are above all of us, both wishcasters, thrillers and downcasters. No matter how much one wishes for something, it is still up to a higher power.
yeah but i'm hoping and thinking that they are mistiming the trough
That's what I say.
lol you guys are unreal...
They might call you a troll next.
My day been busy and it will get so as 90L evovles.
I'm expecting a TD between Friday and Sunday.
I'm still not 100% impressed with convection.
lol i have been posting valuable information on this blog for 5 years i'm no where near a troll but let them call me what they like sometimes you just have to be the better person and look the other way...i call them like i see them and all i'm saying is that the models are showing more of a chance that this storm could miss the U.S all together and i think that is good news but i could be wrong...
Give the system about 4-5 days, then we'll have a much better idea of where it is going once it reached the Antilles.
Statement as of 2:47 PM MDT on August 13, 2009
... Winter Weather Advisory in effect from 6 PM Friday to noon MDT
Saturday for elevations above 5500 feet in Glacier National Park...
The National Weather Service in Great Falls has issued a Winter
Weather Advisory for snow... which is in effect from 6 PM Friday
to noon MDT Saturday for elevations above 5500 feet in Glacier
National Park.
One to two inches of early season snowfall is expected at
elevations above 5500 feet along going to the sun Road in Glacier
National Park Friday night and Saturday morning. Peaks above 7000
feet could receive as much as 6 inches of snow.
Marias Pass... which is at an elevation of about 5200 feet along U.S.
Highway 2... is not expected to receive accumulating snowfall. This
advisory is specifically addressing going to the sun Road and the
high country of Glacier National Park and nearby portions of the
Continental Divide.
Precautionary/preparedness actions...
A Winter Weather Advisory for snow means that periods of snow
will cause primarily travel difficulties. Be prepared for snow
covered roads and limited visibilities... and use caution while
driving.
For specific Road and travel conditions in Montana... dial 5 1 1.
the "wish" part --- In order not to be called a wish/down/west/north/florida/etc caster... you have to just state facts. Once you start giving any type of opinion you become a caster
Amen to that!
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