The tropics are quiet

By: Dr. Jeff Masters , 1:11 PM GMT on September 06, 2009

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Considering that this is historically the peak week of the Atlantic hurricane season, the tropics are quiet. There is an area of disturbed weather in the middle Atlantic (95L) that NHC has been mentioning in their Tropical Weather Outlook the past day, but this disturbance is entering a region of high wind shear and is not a threat to develop.

A strong tropical wave with plenty of rotation is emerging off the coast of Africa this morning, and this wave is a good candidate to show some development this week as it heads west-northwest over the Atlantic. The wave is under about 15 knots of wind shear, and is being developed by several models, including the GFS and ECMWF. However, the models show that this new wave will be pulled northwestward by a strong trough of low pressure this week, and it appears unlikely that the wave will make the long crossing of the Atlantic necessary to threaten any land areas. Another wave with plenty of spin will emerge from the coast of Africa two days from now, and will also have a chance to develop.


Figure 1. Morning satellite image of 95L and a new tropical wave with potential to develop, emerging from the coast of Africa.

An area of concentrated thunderstorms has developed off the North Carolina coast in association with the remains of an old cold front. This system is under about 20 - 30 knots of shear, and is not tropical. However, it will bring heavy rain just offshore of North Carolina's Outer Banks today as it slides north-northeastward along the coast.

I'll have an update Monday.

Jeff Masters

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1194. Dakster
WS - You need to calm down. Go take a "Golden" Panther shower in that bathroom on your avatar...

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What is the A/B high forecasted to do? Right now it looks rather weak, going from an earlier post. (It may have changed in the last several hours so don't flame me if I'm wrong for CURRENT conditions) That may explain the ensemble model trend towards a bend back to the west later in the forecast period.
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1193. scCane
Even if 96l went west there is suppose to be a decent sized trof near the se coast next sunday. More likely than not this thing will be a fish.
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The BAMS does a complete about face!
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Only the AEMN takes 96L west...as of now.
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1190. Patrap
Member Since: July 3, 2005 Posts: 420 Comments: 127543
1188. Relix
Quoting JLPR:


that's storm number 2 to die before reaching PR xD
our shield is definitely working lol


Can only last so much before dying out =(
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1187. Relix
That 96L movement... yeah not liking it =P
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1186. Patrap
Member Since: July 3, 2005 Posts: 420 Comments: 127543
1185. JLPR
Quoting kmanislander:


Precisely. We were very lucky that Erika got sheared out.


that's storm number 2 to die before reaching PR xD
our shield is definitely working lol
Member Since: September 4, 2007 Posts: 36 Comments: 5223
Quoting Drakoen:
Interesting that all the ensembles bring 96L back west or even wsw.


Agreed. Really the first models showing such a trend down the road. Maybe we can't say quite yet that this will curve north and out to sea. Will be interesting to see whether or not the other models join ship and show this trend down the road.
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1183. Patrap
18 Z 96L Statistical/Simple Models (CLIPER,BAMs,LBAR,other Statistical Models)



Member Since: July 3, 2005 Posts: 420 Comments: 127543
Quoting kmanislander:


Precisely. We were very lucky that Erika got sheared out.


Absolutely! Especially with all the convection it generated....if that had become organized and the center was in the middle of the extremely deep thunderstorms....I would be fearful to think what the storm would have become.

HOWEVER...SORRY FOR THE CAPS, BUT THERE IS STILL ABOUT 1 1/2 TO 2 MONTHS OF ACTIVITY WE COULD SEE.....AND IT ONLY TAKES ONE REALLY BAD ONE TO CHANGE THE WHOLE PERSPECTIVE ON THE SEASON.
Sorry for the caps, everyone.
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1181. Nikko
http://www.youtube.com/watch?v=LlhQXu_Xgvc

My Latest thunderstorm video, the wall of water!
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1180. JLPR
Quoting Drakoen:
Interesting that all the ensembles bring 96L back west or even wsw.


that is very interesting =\
so far only one model goes to the west
so those ensembles are making me doubt
Member Since: September 4, 2007 Posts: 36 Comments: 5223
Quoting kmanislander:


Essentially the unique characteristics associated with conditions that produce these waves, including topography, causes them to "spin" as they become areas of low pressure exiting the West African coast as Easterly waves.

See this extract from an article taken from the Nasa Observatory site.

"The last and most common mechanism that triggers the development of a cyclone is the African easterly wave, an area of disturbed weather that travels from east to west across the tropical Atlantic. Essentially, an easterly wave forms because of a “kink” in the jet of air that flows west out of Africa. The jet is created by the strong temperature difference between the Sahara Desert and the Gulf of Guinea. The warm air over the Sahara rises and, several kilometers above the surface, turns southward toward the cooler air over the Gulf. The rotation of the Earth turns this air current westward to form the African Easterly Jet, which then continues out over the Atlantic Ocean. Occasionally, a “kink” will develop in the jet and move from east to west, hence the name easterly wave. Converging winds on the east side of the easterly wave trigger the development of thunderstorms, and some of these large thunderstorm systems go on to become hurricanes. Most Atlantic hurricanes can be traced to easterly waves that form over Western Africa."


Fascinating. Thank you kmanislander. With those massive forces at work, I wonder how many unusual weather phenomena occur over Western Africa around these waves.
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1177. hercj
Quoting iceman55:
look to go wsw any one see this ????


I do.
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***DOUBLE POST***
A lot of the GFS ensemble members take 96L NW, then back towards the west.
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Quoting AllStar17:


i.e. Erika. That could have been a monster if the anticyclone was larger.


Precisely. We were very lucky that Erika got sheared out.
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Quoting Drakoen:
Interesting that all the ensembles bring 96L back west or even wsw.


Yeah.....

Just my feelings.....but I am still keeping an eye on 96L. Never say never with weather....that is the number 1 thing. One never knows.
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Quoting kmanislander:


The difference with this year though is that the pockets of low shear have been very small and that has not allowed for any significant development. In addition, the areas of high pressure aloft have also been rather small and limited in aerial coverage, often imparting shear across developing systems instead of providing ideal conditions aloft for development.

If you think of the Atl and Caribbean so far this year there have not been any large scale areas of favourable conditions. Just pockets here and there.


i.e. Erika. That could have been a monster if the anticyclone was larger.
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1170. Drakoen
Interesting that all the ensembles bring 96L back west or even wsw.
Member Since: October 28, 2006 Posts: 57 Comments: 29886
1169. BDADUDE
Quoting tornadodude:


yeah, he definitely needs banned, im sick of him, i tried to help him, but he gets ridiculous


Im sick oh him to. Its like he dosent care about us. I refuse to be called a fish!!
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Quoting kmanislander:


The difference with this year though is that the pockets of low shear have been very small and that has not allowed for any significant development. In addition, the areas of high pressure aloft have also been rather small and limited in aerial coverage, often imparting shear across developing systems instead of providing ideal conditions aloft for development.

If you think of the Atl and Caribbean so far this year there have not been any large scale areas of favourable conditions. Just pockets here and there.


I mainly agree with this.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
Quoting jasoniscoolman10:
look like a s.


???

Likely to become TD, and eventually Linda.
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Quoting extreme236:


It probably will, but shear isn't forecast to become incredibly hostile until October based on the CFS forecast. It may be hostile right now in the GOM but its not going to stay that way all month. Every season has periods of hostility, and yes no need to tell me this one especially.


The difference with this year though is that the pockets of low shear have been very small and that has not allowed for any significant development. In addition, the areas of high pressure aloft have also been rather small and limited in aerial coverage, often imparting shear across developing systems instead of providing ideal conditions aloft for development.

If you think of the Atl and Caribbean so far this year there have not been any large scale areas of favourable conditions. Just pockets here and there.
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1145. KEEPEROFTHEGATE 9:18 PM EDT on September 06, 2009
Quoting TampaSpin:


Evening all NOTHING can develop in the GOM with the current conditions.....and they are forecast to get even worse.
never say never stranger things have popped up


LOL.......I would always say never when there is Shear at 40kts as are the current conditions in the GOM....If conditions change in the next 48hrs then maybe but, nothing until that time comes.
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1163. hercj
The move back to the west is interesting. The steering currents that take it north must break down if this model is right.
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*OFF TOPIC
I am sorry for those who like my graphics. I should have my computer back in a couple weeks....so I can get back to posting the graphics that some of you like. Sorry for any inconveniences .
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now you see it now you dont
Member Since: May 21, 2006 Posts: 5091 Comments: 114712
1160. KEEPEROFTHEGATE (Mod)
the window for dev is still open at the moment cv season still got 2 weeks and 4 days then we get into the sweeping fall cold fronts dropping down the plains and builting return flows off gom nw carb still a possible 4 more events excluding 96l which will should be fred
Member Since: July 15, 2006 Posts: 169 Comments: 53296
Quoting BurnedAfterPosting:
WS seriously you need to get over yourself


I know, its so annoying. Half this blog has him on ignore.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
A lot of the GFS ensemble members take 96L NW, then back towards the west.
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Quoting Leafgreen:
Q: The last few invests to come off the African coast have had "spin". Why do these waves have spin? Do they have spin over land or do they immediately acquire it when over water? If they have spin over land, why don't large storms over other continents, such as supercells over CONUS or Colombia, have spin?


Colombia does produce a repetitive low that ejects from the NW coast into the SW Caribbean all the time. This low is created by the terrain that develops thunderstorms in that area but the low itself usually peters out over water. It is also referred to as the perennial Colombian low.
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1152. BurnedAfterPosting 1:19 AM GMT on September 07, 2009
WS seriously you need to get over yourself


lol, that will never happen....
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this year re mine me of 2006 kind of
Member Since: May 21, 2006 Posts: 5091 Comments: 114712
A lot of seasons after El Nino years tend to be above average.
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WS seriously you need to get over yourself
It is scary to think what next year may bring.
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Quoting kmanislander:


Actually I think the entire season may end early. Shear has been high from June 1st and there are no signs that it will abate any time soon. I am concerned that if anything were to form in the Caribbean in October or November it could become quite intense very quickly. We will have to wait and see but shear looks to be king this year.


It probably will, but shear isn't forecast to become incredibly hostile until October based on the CFS forecast. It may be hostile right now in the GOM but its not going to stay that way all month. Every season has periods of hostility, and yes no need to tell me this one especially.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
1149. JLPR
Quoting AllStar17:


First couple of model runs shall be taken with a grain of salt.


that's right
Member Since: September 4, 2007 Posts: 36 Comments: 5223
1148. hercj
The Year of Shear!!!
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Quoting JLPR:


more models running on 96L


First couple of model runs shall be taken with a grain of salt.
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1145. KEEPEROFTHEGATE (Mod)
Quoting TampaSpin:


Evening all NOTHING can develop in the GOM with the current conditions.....and they are forecast to get even worse.
never say never stranger things have popped up
Member Since: July 15, 2006 Posts: 169 Comments: 53296
Quoting WeatherStudent:
Not cool, EX. THANK GOD that you have absolutely no saying in regards to who cant and who cannot blog on this blog. I praise to the Lord one million times for that being the actual case. Anyways, back to the 96L disussion going on here tonight. Kman, so your seeing an early demise to this year's Cape Verde Season, then? Also, what are your initial thoughts on what might await the Carib. during Oct. since that's typically the month that both you and I tend to be in the greatest threat for TC strikes, sir?


Actually I think the entire season may end early. Shear has been high from June 1st and there are no signs that it will abate any time soon. I am concerned that if anything were to form in the Caribbean in October or November it could become quite intense very quickly. We will have to wait and see but shear looks to be king this year.
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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.