TD 2 struggling; new African wave bears watching
Tropical Depression Two is struggling. The depression still has a good chance of becoming the Atlantic hurricane season's first named storm this week, but the dry, Saharan air that surrounds the storm, combined with moderately high levels of wind shear, are interfering with the storm's organization. Satellite loops of the storm show that heavy thunderstorm activity is limited to the west side of the depression. This is due to strong winds out of the southeast that are creating a moderate 15 - 20 knots of wind shear. The intensity and coverage of these thunderstorms is meager, thanks to the large amount of dry air to TD 2's north that is getting wrapped into the circulation. This morning's QuikSCAT pass showed a well-formed surface circulation, with top winds of about 30 - 35 mph.
Wind shear over TD 2 is expected to remain in the moderate range, 10 - 20 knots, over the next five days. Sea Surface Temperatures (SSTs) are a marginal 26 - 27°C, and will not change much over the next three days. There is plenty of dry, stable air from the Saharan Air Layer (SAL) to to TD 2's north 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. However, it does appear likely that TD 2 has enough going for it that it will eventually be able to become Tropical Storm Ana sometime in the next three days. Most of the computer models show some weak development, but none of them predict TD 2 will become a hurricane. It is unusual for storms forming this far north to make it all the way across the Atlantic to hit the Lesser Antilles Islands. For now, TD 2 doesn't concern me as much as the new tropical wave to its southeast, just off the coast of Africa.
Figure 1. Tropical Depression Two (left center of image) and a new tropical wave (right side of image), newly emerged from the coast of Africa.
Elsewhere in the Atlantic
A strong tropical wave with some rotation and plenty of heavy thunderstorm activity left the coast of Africa yesterday, and is located a few hundred miles south of the Cape Verdes Islands. The GFS and ECMWF models continue to predict the development of this wave late this week. Both of these models indicate that the wave would track further south than Tropical Depression Two, and could impact the Lesser Antilles Islands in about seven days. This storm bears close attention over the coming days.
Two other tropical waves, one that just passed through the Lesser Antilles Islands, and one about 300 miles east of the islands, are mentioned in NHC's Graphical Tropical Weather Outlook. Both of these waves have very limited heavy thunderstorm activity that is not increasing, and are not a threat to develop over the next two days. None of the computer models develop either of these waves.
Felicia moves through Hawaiian Islands as a tropical depression
Tropical Storm Felicia weakened to a tropical depression before passing through the Hawaiian Islands yesterday. The storm brought scattered heavy rains of 1 - 2 inches to the islands, and no damage was reported. Felicia is only the 10th tropical cyclone of tropical depression strength or higher to hit the islands since 1950. Four other tropical cyclones have passed within 75 miles of the islands during that time period.
Be careful clicking on external links in blog comments
A comment may have been posted on my blog over the weekend containing links to a malicious web site that infected some people's computers when they clicked on the link. The exact link responsible has eluded us thus far, and we are also investigating the possibility that a bad banner ad was responsible. To provide an extra layer of protection, we've installed software on the blogs that will now warn users that they are leaving the site when they click on an external link, so that one has do an extra click to go to an external site. This will give users an opportunity to think twice before clicking on a potentially dangerous link. I apologize to anybody who may have been affected by the attack. Please submit a support ticket to help us out in the future for any issues of this nature.
I'll have an update Thursday morning.
Jeff Masters
Reader Comments
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According to the COMET module here: http://www.meted.ucar.edu/nwp/pcu2/namdom3.htm it uses a previous GFS forecast (obviously does not wait for GFS to finish the current one).
"Generally, in the NAM WRF-NMM Model, the values of T, q, u, and v are prescribed along the outer two rows of grid points. The values at these points are never modified by the model predictive equations, but rather are updated from an earlier GFS model run."
So, this, to me, means that 0 Z NAM uses the 18 Z GFS for boundary conditions and the 12 Z NAM uses GFS 06 Z...yeesh. Could that be true? No wonder I refer to NAM as little as possible.
Haha thank you so much!
Thanks Storm, I read your blog this morning! I guess I was puzzled because I remember the NHC or Jeff Masters calling for favorable shear on the storm for a while now. Thank you for answering!
Skyepony Blobs Galore 44 0 8 hours ago -61 second ago
Not looking that impressive, shear and dry are penetrating the system pretty harsh right now. Durinal Minimum isn't helping TD-2 either.
Wouldn't be all that shocking if TD-2 didn't amount to more than a 45 MPH system although I do think TD-2 will be named.
Hi WeatherStudent......
BBL watching the rest of the RAYS game....LOL
0-0-0
Thanks, thats what was I was thinking. I was looking at the 18Z NAM for today and it brought a disturbance into its domain from the Atlantic. I looked at the previous GFS to see if it could be passing it into the NAM, but the timing did not make sense.
Ana been eaten by Bill? WOw!!!
Usually, 45 mph storms are named.
Off to clean my monitor now.
what's the bet.....
This is the one: http://www.meted.ucar.edu/
Entirely written and built by professionals and university profs. Also free.
That is crazy. When he posed the question I had googled it and saw the same presentation from UCAR...but didn't bother signing up to see it.
Now I'm confused. I thought for sure the NAM assimilates satellite and radar data???
How would old GFS boundary conditions blend with this new data?
Obviously they have to interpolate to a finer grid in the NAM anyways...but still...
I always think that the lines of clouds emanating from a slightly sheared storm make it prettier
Correct me if Im wrong, but is that a surface trough in the GOMEX?
thanks stormw, this was so funny....
Watch out for that Skye, she controls time! Do not make her angry!
How was that for naming denial craziness?
i was talking about the fruitcake..lol
other than for my information is it anything i can get creditialed or degreed out of? I suspecting free means no. But i appreciate the info greatly. Working a full time job and interested in going back and doing what i should have done.
I would imagine there is plenty of MADIS and satellite profile assimilation, but still...seems goofy. But what do you do if you need global model boundary conditions and cannot wait for GFS's assimilation period?
In our shop, we wait for it just like everyone else (like GFDL)...except NAM.
That is at least a subtropical storm.
omg omg omg
is this for real?
i hope this is what it looks like... real quality education for free...
if it is, this truly is the future
12Z Models really trending toward what I went into late lastnight about TD2 possibly getting wrapped together with the big blob behind it.
Today's rgb loop~ the exposed low level clouds (the yellow ones) to the north & east~ rushing out like an outflow boundry. Taking some brutal shear.
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