Invest 94L and the Lesser Antilles

By: Dr. Jeff Masters , 9:51 AM GMT on August 30, 2009

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Hi, this is Dr. Rob Carver filling in for Dr. Masters. The convection associated with Invest 94L has intensified, prompting the NHC to issue an early Tropical Weather Outlook to update the situation. Essentially, people in the Lesser Antilles need to start paying attention to the seas and skies. Looking at the computer track models, the set of model solutions are fairly similar to the Saturday model runs. A set of dynamical models (GFDL, HWRF, NOGAPS) runs to the NE of the Antilles, while the simpler models (LBAR, BAM family) are more easterly and take 94L over the Antilles. I do not ascribe any significance to the 00Z GFS track following the simpler models over the dynamical models. From my examination of the 00Z GFS run, it looks like the simulated 94L weakens too much, so the automatic vortex tracker picks up another vorticity feature. As for the future of 94L, there is a large area of large wind shear to it's north. It will need to keep it's track at WNW-W for intensification.

Update at 6AM EDT
I would be remiss if I didn't mention the major hurricane in the Eastern Pacific, Jimena At this time, Jimena has a satellite-estimated maximum wind speed of 115 mph, making it a Category 3 storm on the Saffir-Simpson scale. Jimena has an impressive presentation in satellite imagery with a large area of cold anvil cirrus in the center of the storm. The following microwave imagery indicate the formation of a relatively potent central eyewall, which is responsible for intensification.


Fig. 1 SSMI 85 GHz PCT at 0244Z Aug 30. Image courtesy of NRL.


People along the western coast of Mexico and along along the Baja need to pay close attention to this dangerous storm. I emphasize that using the current track and intensity forecast, Jimena will be a Category 4 storm when it approaches the tip of Baja and a Category 3 storm when it makes landfall up the coast.

It is worth noting that if Jimena follows the more easterly tracks presented in the computer track forecasts, the remnants of Jimena could impact NM and western Texas.


I'll update this entry further in response to 94L's development.


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30/2345 UTC 12.4N 48.4W T1.0/1.5 94L -- Atlantic
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Quoting StormFreakyisher:
Someone please tell me why this is a code red when there is 30-40knt shear to its NW?Please!
That's the anticyclone. That is REALLY favorable conditions. :)
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Quoting StormFreakyisher:
Someone please tell me why this is a code red when there is 30-40knt shear to its NW?Please!
Quoting futuremet:
94L is a total mess; it needs to regenerate some convection tonight before traversing high shear regions over the next couple of days.


Apparently im going to have to repost this many more times.

"That shear is due to the upper level anticyclone protecting Invest 94L and its interaction with an upper level low well to the north. Invest 94L will never encounter this shear as the upper-level anticyclone will be moving in tandem with the system."
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2305. Relix
Quoting CaribBoy:
Interesting. ERIKA 1997


Like mother like daughter? This one should track very similar to that, with the exception of not recurving that quickly.
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Ah. What I was waiting on....



...SPECIAL FEATURES...

AN ACTIVE TROPICAL WAVE EXTENDS FROM 18N45W TO 8N49W WITH AN
ASSOCIATED 1007 MB SURFACE LOW CENTER NEAR 11N48W. THE WAVE IS
MOVING W NEAR 15 KT. SATELLITE IMAGERY INDICATES ELONGATED
CYCLONIC FLOW IN THE VICINITY OF THE WAVE AXIS CONCENTRATED
AROUND THE LOW CENTER. SCATTERED MODERATE/ISOLATED STRONG
CONVECTION IS MAINLY TO THE NW OF THE WAVE AXIS FROM 14N-18N
BETWEEN 47W-49W..AND TO THE W OF LOW CENTER FROM 8N-14N BETWEEN
48W-54W. THIS SYSTEM HAS A HIGH CHANCE...GREATER THAN 50
PERCENT...OF BECOMING A TROPICAL CYCLONE IN THE NEXT 48 HRS.
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Someone please tell me why this is a code red when there is 30-40knt shear to its NW?Please!
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94L is a total mess; it needs to regenerate some convection tonight before traversing high shear regions over the next couple of days.
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Quoting IKE:


NHC has no update at 11 pm.
Maybe he was implying something by that, Ike....lol
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2299. Drakoen
Quoting Max1023:


It shows the MLC alright, the rotation in the higher clouds, it also suggests that 94L's moisture field is moving at a heading of maybe 285-290, or WNW, if it keeps going that way Puerto Rico and Hispaniola will need to watch this system. The carribean is full of very warm water, if the upper anticyclone continues to protect 94 from shear then a strong hurricane is a possibility.


That product is representative of the lower to mid levels and 94L does not have a well-defined circulation.
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Quoting TampaSpin:
For those that are interested. Here was my blog update from last nite. Everything stays current with the graphics. I'm going to eat some dinner and work on an update to have out before 11pm before NHC releases there. I love to try to beat them to the punch....LOL....j/k
Thanks Tampa...enjoy your dinner, doing the same here...out for now
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2297. IKE
Quoting TampaSpin:
For those that are interested. Here was my blog update from last nite. Everything stays current with the graphics. I'm going to eat some dinner and work on an update to have out before 11pm before NHC releases there. I love to try to beat them to the punch....LOL....j/k


NHC has no update at 11 pm.
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2296. JRRP

.see you later
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For those that are interested. Here was my blog update from last nite. Everything stays current with the graphics. I'm going to eat some dinner and work on an update to have out before 11pm before NHC releases there. I love to try to beat them to the punch....LOL....j/k
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2294. Max1023
Quoting Drakoen:
This shows a center near 13N


It shows the MLC alright, the rotation in the higher clouds, it also suggests that 94L's moisture field is moving at a heading of maybe 285-290, or WNW, if it keeps going that way Puerto Rico and Hispaniola will need to watch this system. The carribean is full of very warm water, if the upper anticyclone continues to protect 94 from shear then a strong hurricane is a possibility.
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Quoting Max1023:


The H-Boxes are suspect at best, and anyway only apply to major hurricanes, 94L will likely only be a moderate to strong TS by then, unless it doesn't develop or develops extremely rapidly. It does't matter whether or not 94L hits the H-box.


Thanks. Didn't know intensity mattered in that regard.
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Quoting TampaSpin:


True but, do you remember what it looked like last nite at this time.....Many was writing 94L off.....Tonite it blows up big time...someone just posted something about Shear in its front...funny if you look at a WaterVapor loop the shear is moving away from 94L at about the same pace it is moving...


Yeah....which means if it does the same tonight it would look MUCH better than it even did this morning.
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I will caution that I am no way qualified to interpret the QuikScat ambiguities. We will know within an hour or so where NHC places a center.
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2290. Max1023
Quoting mikatnight:


You sound pretty knowledgable...any opinion on 94L going into the H-box?


The H-Boxes are suspect at best, and anyway only apply to major hurricanes, 94L will likely only be a moderate to strong TS by then, unless it doesn't develop or develops extremely rapidly. It does't matter whether or not 94L hits the H-box.
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Luckily, I was still pretty much packed from my trip to Bermuda last weekend...so I'm not hustling too much right now.

However, I do have to get up at 2:00 AM for my 6:00 AM flight...so there is that.

In the meantime...I've decided to go ahead and release my August 2009 GOES East Infrared Hurricane Alley / Sector Animations one-day ahead of schedule.

Those animations will be up on YouTube by 10:00 PM Eastern.
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2288. IKE
Quoting Stormchaser2007:


"That shear is due to the upper level anticyclone protecting Invest 94L and its interaction with an upper level low well to the north. Invest 94L will never encounter this shear as the upper-level anticyclone will be moving in tandem with the system."


For it's future, you better hope it never encounters that shear. I'm assuming the ECMWF thinks it will and that's why it shows a wave with 94L, only.
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2287. Drakoen
This shows a center near 13N
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Quoting Vortex95:
quickscat has a southy bias? didn't know that.

A SW bias, yes. We (nrt and I) posted a recent NHC paper sometime a couple of months ago. It is a relatively new open discussion of QuikScat's limitations.

The pdf paper: http://www.nhc.noaa.gov/pdf/brennan-et-al-wf09.pdf
I see nrt posted it...but the link is buggered up.
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Quoting Chavalito:
I think that 94L will be poof during night. It's El Nino year so we are safe in the great Antilles from being impacted by a hurricane. 94L won't come to our Island...
Donde vives?
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Quoting AllStar17:


Well.....all it'd have to do is do a repeat of last night and it SHOULD be called a Tropical Depression.


True but, do you remember what it looked like last nite at this time.....Many was writing 94L off.....Tonite it blows up big time...someone just posted something about Shear in its front...funny if you look at a WaterVapor loop the shear is moving away from 94L at about the same pace it is moving...
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impressive outflow in gom
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Quoting Stormchaser2007:


Just becuase its an El nino year doesnt mean that one place is immune to hurricanes.


Some people on here just do not understand.
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Quoting TampaSpin:


Just logged on and haven't really looked at it most of the day...had an adventures day today....



ULL (upper level lows)
Thanks Tamps..looking forward to your input as always appreciated...hope your day was good...pretty rainy here today
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2280. Max1023
Quoting SLU:
There's one way to find the answer to all our questions ......... SEND THE RECON TO INVESTIGATE!!

01/1800Z is an awfully long wait ....


The recon would likely find several lower level swirls in an ill-stacked system with the MLC northeast of the surface reflection. By the 1st 94 will probably be better organized, as of now it is not strong enough to really threaten the antilles, but if 94 becomes a TD tonight or tomorrow the recon will likely be moved up in the interest of safety. No point is wasting a mission on an invest until it is obvious that it threatens land, which would be by Tuesday.
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am reding them i this like massing with evere one
Member Since: May 21, 2006 Posts: 5091 Comments: 115247
I must say with the exception of Bill we have had some odd, non-typical systems this year.

94L has excellent structure. The only thing missing is "meat on its bones". The lack of central convection with no other inhibiting factors is very confusing.
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Interesting. ERIKA 1997
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Quoting SavannahStorm:


I'm quite envious. Can't wait to see the footage, all I've seen from Bermuda regarding Bill is video of tourists staring at the ocean, lol.


And that's all I've seen, too.

When I edited the video, I did put in a 10-second shot of tourists looking at the surf...but then I cut it.

You guys deserve all the cool stuff...which I did provide in the 10-minute video.
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Quoting Tazmanian:
yup 94L dos not have march time life in its life it will soon to be going in too 30kt to 40kt of wind shear



Are you reading the blog posts? Look at Post 2263.
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Quoting Chavalito:
I think that 94L will be poof during night. It's El Nino year so we are safe in the great Antilles from being impacted by a hurricane. 94L won't come to our Island...


Just becuase its an El nino year doesnt mean that one place is immune to hurricanes.
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Quoting Max1023:
Looking at the 12.5 kn resolution, it looks like the surface centre, which has existed since 94l was south of the cape verdes, has drifted westerly with the shallow flow, while the MLC is tracking more north and slower. The result is the surface curculation becoming ill-defined as the MLC trys to build towards the surface while fighting the vorticity at the lower levels, thats why the 850mb vorticity is farther north than you would expect. The MLC seems to be at about 13N 49 W, or thereabouts, and the interaction between the ill stacked centres is producing multiple minor swirls. Also, you can see an area of light winds just to the north of the LLC, thats where the two circulations are fighting it out to see which will become dominant. According to the spiral bands in the convection, it seems that the northerly circulation will likely prevail, as the MLC builds to the surface, since the LLC has no upper level support and is already becoming ill-defined. DMAX tonight may help in 94l's organization by allowing the convection which has habitually formed to force the circulations to stack. 94L is moving north of west, however the lower level circulation is not following this motion as of yet, as it is not being influenced by the deeper flow that moves the higher circulation. With a disorganized system like 94L movement is often rather erratic until it consolidates, which I believe can happen over the next 12 hours providing 94 forms a moderate to large amount of convection over its MLC, allowing it to become dominate.


You sound pretty knowledgable...any opinion on 94L going into the H-box?
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Quoting SLU:
There's one way to find the answer to all our questions ......... SEND THE RECON TO INVESTIGATE!!

01/1800Z is an awfully long wait ....


Yeah.....sitting on pins and needles until then.
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Quoting KATRINABILOXIGIRL:
What is your take on 94L this evening Tampa?


Just logged on and haven't really looked at it most of the day...had an adventures day today....

Quoting somemalayguy117:
The area where 94L is located is pretty moist. Can anyone explain what are those two rotating systems north of 94L?


ULL (upper level lows)
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2270. flsky
Just talked w/my son who, along w/his girlfriend, is still on his way to Cabo tomorrow morning. I explained to him how to read comments on this blog, so if anyone has up-to-date info you can offer, he, and I, would be quite appreciative. I doubt if he'll have web access after tomorrow, but between now and tomorrow morning he'll be checking in.
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I think that 94L will be poof during night. It's El Nino year so we are safe in the great Antilles from being impacted by a hurricane. 94L won't come to our Island...
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yup 94L dos not have march time life in its life it will soon to be going in too 30kt to 40kt of wind shear
Member Since: May 21, 2006 Posts: 5091 Comments: 115247
2267. Drakoen
The ambigous quickscat also matches up well with the cimss 850mb vorticity as well as MIMIC-TPW
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Quoting TampaSpin:
Dmx for 94L could bring us something we do not want to see tomorrow morning.


Well.....all it'd have to do is do a repeat of last night and it SHOULD be called a Tropical Depression.
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2265. SLU
There's one way to find the answer to all our questions ......... SEND THE RECON TO INVESTIGATE!!

01/1800Z is an awfully long wait ....
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Quoting IKE:
NHC probably did the wise thing keeping it red for now.

Has anyone looked at the updated(2100UTC) shear map? Here's the link also..Link It looks boxed into a corner almost.



"That shear is due to the upper level anticyclone protecting Invest 94L and its interaction with an upper level low well to the north. Invest 94L will never encounter this shear as the upper-level anticyclone will be moving in tandem with the system."
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2262. Max1023
Looking at the 12.5 kn resolution, it looks like the surface centre, which has existed since 94l was south of the cape verdes, has drifted westerly with the shallow flow, while the MLC is tracking more north and slower. The result is the surface curculation becoming ill-defined as the MLC trys to build towards the surface while fighting the vorticity at the lower levels, thats why the 850mb vorticity is farther north than you would expect. The MLC seems to be at about 13N 49 W, or thereabouts, and the interaction between the ill stacked centres is producing multiple minor swirls. Also, you can see an area of light winds just to the north of the LLC, thats where the two circulations are fighting it out to see which will become dominant. According to the spiral bands in the convection, it seems that the northerly circulation will likely prevail, as the MLC builds to the surface, since the LLC has no upper level support and is already becoming ill-defined. DMAX tonight may help in 94l's organization by allowing the convection which has habitually formed to force the circulations to stack. 94L is moving north of west, however the lower level circulation is not following this motion as of yet, as it is not being influenced by the deeper flow that moves the higher circulation. With a disorganized system like 94L movement is often rather erratic until it consolidates, which I believe can happen over the next 12 hours providing 94 forms a moderate to large amount of convection over its MLC, allowing it to become dominate.
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From 8:15am to 6:45pm...

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The area where 94L is located is pretty moist. Can anyone explain what are those two rotating systems north of 94L?
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30 Aug 2009 23:15 UTC [2 km resolution]

Image centered at Latitude= 13.33° N Longitude= 50.59° W (X=625 Y=319)
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2258. 7544
Quoting JRRP:

the structure looks like TS


agree and it just might be at dmax
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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.

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