A very busy day in the tropics; wind shear tutorial posted

By: Dr. Jeff Masters , 2:10 PM GMT on September 25, 2007

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Satellite imagery and this morning's QuikSCAT pass show a vigorous surface circulation that continues to spin in the Gulf of Mexico, about 280 miles south-southeast of Brownsville, Texas. This disturbance (94L) has one clump of heavy thunderstorms on the northern side of the circulation, and QuikSCAT saw winds up to 25 mph at 8:14 am this morning. Wind shear has fallen to about 10 knots over the disturbance, and is expected to remain 10 knots or below for the next three days. This should allow 94L to develop into a tropical depression later today or on Wednesday. Steering currents are weak in the southwest Gulf of Mexico, and 94L will move slowly and erratically. This storm is primarily a threat to Mexico, due to a very strong ridge of high pressure expected to remain in place over the Gulf of Mexico the rest of the week. Several of the models foresee an eventual landfall to the west or south between Tampico and Campeche late this week. A Hurricane Hunter flight is scheduled to investigate 94L this afternoon.

Lesser Antilles disturbance 97L needs to be watched
A tropical wave (97L) was near 15N 62W, or just west of Dominica and Martinique in the Lesser Antilles Islands at 8 am EDT this morning. This wave had a closed circulation yesterday, but this circulation degenerated and was no longer fully closed on this morning's QuikSCAT pass. Top winds from QuikSCAT were about 30 mph just to the northeast of the northernmost islands in the chain. None of the islands had winds exceeding 15 mph between 8 am and 9 am EDT this morning. Satellite imagery shows heavy thunderstorm activity mostly died out last night, but is now making a comeback, with some major cells blowing up over Guadaloupe. A surface circulation also appears to be trying to form under these new cells. The wave is under about 10-20 knots of wind shear. The shear is forecast to remain near 20 knots through Thursday, which may allow some slow development. The 06Z (2 am EDT) run of the GFDL model did develop 97L into a weak tropical storm. The forecast had 97L moving over Puerto Rico on Wednesday, the Dominican Republic on Thursday, and eastern Cuba by Saturday. The 06Z HWRF model did not develop 97L. If 97L does develop, and survives passage over Hispaniola and Cuba, and survives some possible encounters with areas of high wind shear, it could arrive at the Florida coast on Sunday as a tropical storm. That's a lot of "ifs", and there is only about a 5% chance of this happening. The Hurricane Hunter mission for this afternoon into 97L was canceled, and no new missions are scheduled.

Links to follow for 97L
Martinique radar
Puerto Rico long range radar


Figure 1. Microwave image from 4:39 am EDT today showing low-level spiral banding coming together in Karen. This image is bit different from the usual 85 GHz images I show, which emphasize where it is raining through the total depth of the storm. The image above is taken at 37 GHz, where one sees more of the surface structure of the storm. Image credit: Navy/NRL.

Tropical Storm Karen forms
Tropical Storm Karen formed this morning, midway between Africa and the Lesser Antilles Islands. This large storm is still disorganized, as seen in the latest satellite loops. Low level spirals bands are slowly organizing, and with wind shear 10 knots or less, Karen should be able to steadily strengthen to a hurricane, as predicted by the SHIPS and GFDL intensity models. The HWRF model keeps Karen just below hurricane strength. Later this week, Karen may encounter a region of hostile wind shear in association with a trough of low pressure that will also turn the storm to the north or northwest. This may slow or reverse Karen's intensification.

It currently appears that Karen will not affect any land areas. It is unusual for a hurricane to turn west and hit the U.S. after going as far north as the official NHC forecast has the storm five days from now. The GFS model has consistently shown that Karen will recurve out to sea east of Bermuda next week. However, the UKMET model is showing a more southerly track just north of the Lesser Antilles islands six days from now. Should Karen follow this track, the storm may miss the trough the GFS is predicting will recurve it. In this case, Karen could be a long-range threat to Bermuda or the U.S. East Coast.

Disturbed weather over Florida and the Bahamas
An area of disturbed weather has formed over South Florida and the western Bahama Islands, in association with an upper-level trough of low pressure. The region is under about 20 knots of wind shear, which should prevent any development. This disturbance is bringing heavy rain to portions of South Florida, the Bahamas, and Cuba, as seen on long range radar out of Key West.

Hurricane Center Directorship open
The position of director of the National Hurricane Center is officially open, according to a story published today in the Miami Herald. The current acting director, veteran hurricane forecaster Ed Rappaport, will decline to apply. "The timing of this position is not right, both personally and professionally, so I have chosen not to apply," said Rappaport, 49. Leading candidates for the job include the current interim deputy director, Bill Read, and hurricane specialist Rick Knabb.

Wind shear tutorial
For those interested, I've posted a wind shear tutorial. This page is permanently linked on our tropical page.

I'll have an update Wednesday morning at the latest.

Jeff Masters

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2707. HIEXPRESS
3:06 AM GMT on May 06, 2008
NAO
Member Since: October 13, 2005 Posts: 4 Comments: 2156
2706. Patrap
3:00 PM GMT on September 26, 2007
NEXRAD Radar
Miami Base Reflectivity 0.50 Degree Elevation Range 248 NMI 20 frame Loop

Link
Member Since: July 3, 2005 Posts: 427 Comments: 129435
2705. moonlightcowboy
2:35 PM GMT on September 26, 2007
How come the CIMSS is showing an INVEST at 10n,40w and the WU site isn't? Of course the CIMSS site is not showing 98L at sFL either?

MLC <----------confused!
Member Since: July 9, 2006 Posts: 184 Comments: 29610
2704. Ivansvrivr
2:32 PM GMT on September 26, 2007
The my discussion with Drak is panning out just as figured. I'm not trying to "serve crow" after all quite a bit of what I've learned to have that discussion came From Draks blog. It just seemed like something was going to thow a curve ball at the models. La nina is skewing the models late season. they should reset the dates on the computers(as if it were possible) to Aug 31 or so.
2703. youradjuster
2:31 PM GMT on September 26, 2007
He might have, but after doing a refresh it is still showing yesterdays blog
2701. ncsmiles
2:28 PM GMT on September 26, 2007
Dr. Masters has put out a new blog guys
2700. flzepher
2:27 PM GMT on September 26, 2007
Remember last week how many people were saying season in over, bust, and ect. Well granny was serving pickled crows feet on the Beverly Hillbillies this morning. I hear they are good with grits.
2699. NEwxguy
2:27 PM GMT on September 26, 2007
The upper pattern flow is under going a lot of changes in the coming week,so it's real hard to pinpoint anything at this point.I think the whole east coast has to watch this closely
Member Since: September 6, 2007 Posts: 887 Comments: 15970
2698. nrtiwlnvragn
2:26 PM GMT on September 26, 2007
New Blog
Member Since: September 23, 2005 Posts: 14 Comments: 11305
2697. Ivansvrivr
2:24 PM GMT on September 26, 2007
I've said for days that the bermuda high has showed up to the party late. Very typical La Nina pattern. We may as well take our calenders and flip them back a page to September.
2696. youradjuster
2:24 PM GMT on September 26, 2007
Has anyone looked at what the CMC computer is projecting for 98l To cross Florida, skirt the east coast, go out to sea around VA, build to a major storm and do a 180% turn and smash into NC
2695. ncsmiles
2:24 PM GMT on September 26, 2007
Dr. masters just updated
2694. Bonedog
2:22 PM GMT on September 26, 2007
storm what I am saying is as this minute looking at the latest info I don't see the recurve out to sea.

But as the post i made earlier shows that in the span of 3 hours the winds changed as the chart shows. So it can change again in the next 3 hrs.

Member Since: July 14, 2005 Posts: 14 Comments: 7418
2693. Eyewall911
2:22 PM GMT on September 26, 2007
Were they calling for Andrew to go out to sea also?
2692. CJ5
2:21 PM GMT on September 26, 2007
I agree that the 7/23 disturbance will be the next invest. It looks quite impressive as does the QS.

Karen finally consolidated her power and should begin to intensify. I notice the tracks have shifted as well. I shifted mine more N this am but still do not think it will be as pronounced a N turn as some models are still predicting. The pressure models diverge a little on the H and its strength. NGPS shows a complete breakdown along the EC in 72-96 hours and maintains that for several days. That certainly could mean a fish but they have shifted all over the place the last few days.
Member Since: July 4, 2007 Posts: 0 Comments: 1755
2691. Ivansvrivr
2:21 PM GMT on September 26, 2007
Seems like S.fl has gone over to steady tropical type rain.
2690. Bonedog
2:20 PM GMT on September 26, 2007
rareaire its way early but the entire east coast should monitor it. At least we have several days and opportunities for this to get kicked out to sea.
Member Since: July 14, 2005 Posts: 14 Comments: 7418
2689. SavannahStorm
2:20 PM GMT on September 26, 2007
Here's a storm that tracked well north of Puerto Rico and then took a turn for the worst.


http://www.wunderground.com/data/dhc_archive_charts/at_1992_charts/at199202.gif

Member Since: September 22, 2005 Posts: 18 Comments: 2343
2688. stoormfury
2:19 PM GMT on September 26, 2007
bonedog
what are you saying that KAREN will not recurve and that it will track a west track
Member Since: August 22, 2006 Posts: 0 Comments: 2722
2687. Floodman
2:19 PM GMT on September 26, 2007
Thank you, Ivan...I think we're all a bit odd, for just the reason you cite
Member Since: August 2, 2006 Posts: 10 Comments: 9922
2686. Ivansvrivr
2:18 PM GMT on September 26, 2007
Outflow from Karen may tend to strengthen that high
2685. Bonedog
2:18 PM GMT on September 26, 2007
eyewall it was 2hrs ago but it takes the models a few hours to run and be posted up say figure around noonish before we see any of them
Member Since: July 14, 2005 Posts: 14 Comments: 7418
2684. hurricane23
2:17 PM GMT on September 26, 2007
98L should bring rainy conditions for south florida before moving out towards the NE.
Member Since: May 14, 2006 Posts: 8 Comments: 13841
2683. PensacolaDoug
2:16 PM GMT on September 26, 2007
Anybody know whats up with the Key West radar?
Member Since: July 25, 2006 Posts: 0 Comments: 647
2682. hurricane23
2:16 PM GMT on September 26, 2007
Here is the image i created for possible 99L...

gg
Member Since: May 14, 2006 Posts: 8 Comments: 13841
2681. Ivansvrivr
2:16 PM GMT on September 26, 2007
I actually agree with both of you about Bastardi. Hes not afraid to go out on a limb with a forecast. I do think He's a little loopy at times but coming from me thats kind of a complement. thats why I'll red storms blog, Draks Dr.Masters and Bastardi's forecast on accu too. I like getting differing opinions. It doesn't hinder ones learning process to gather differing ideas. If I seemed like i was insulting him, I wasn't. Like I said earlier, Bastardi's "unique" take on things actually fits the "unique" conitions at the moment. Takes one to forecast one. if you think about it a bunch of folks staring at sattelite photos and computer models of hurricanes is a bit odd in itself.
2680. medic2luv
2:16 PM GMT on September 26, 2007
Storm J,
what's your take on 98L?
Member Since: August 13, 2007 Posts: 0 Comments: 189
2679. rareaire
2:16 PM GMT on September 26, 2007
quick question from the mets on here. If the high sets and karen goes west what are the possible impact points for this. I see several bloggers have said if it goes west nw sheer will kill it. If it goes north its out to sea. Im just curious as this thing is huge strong and growing by the minute yet still way south. I know its a long way off but your opinion would be appreciated.
Member Since: August 19, 2007 Posts: 0 Comments: 1601
2678. Eyewall911
2:14 PM GMT on September 26, 2007
When is 12Z
2677. weathermanwannabe
2:14 PM GMT on September 26, 2007
Appears, right now, that Karen is moving towards the NW, so the strength of the "forecated" ridge (enough to turn it more west) vs. the timing of the trough will be the other factor to watch....On top of that, if the storm weakens (also as forecast by the models in terms of shear values), it will not be as affected by any weakness to the north...Thus, it is still to early, IMHO, to say that Karen will be a fish.....
Member Since: August 8, 2006 Posts: 0 Comments: 9376
2676. Floodman
2:14 PM GMT on September 26, 2007
weathers4me, it has to do with gradient, among a great many other things, but a weaker high creates less "edge" to follow (at least that's my understanding of it)...not as much differential creates less of a groove for it to follow
Member Since: August 2, 2006 Posts: 10 Comments: 9922
2675. hurricane23
2:14 PM GMT on September 26, 2007
Not a real significant shift but to its about 5 percent it makes all the way to the coast before another trof kicks it out.
Member Since: May 14, 2006 Posts: 8 Comments: 13841
2674. StormJunkie
2:14 PM GMT on September 26, 2007
That would be a real problem 785, but not completely out of the question imho.
Member Since: August 17, 2005 Posts: 26 Comments: 16874
2673. Bonedog
2:13 PM GMT on September 26, 2007
wetahers look at where the high is and remeber the circulation around the high is clockwise. A storm cant ride around the High counter to the way its winds are so with the high building in where it shows the storm will track twords the west riding the perifery
Member Since: July 14, 2005 Posts: 14 Comments: 7418
2672. StormJunkie
2:13 PM GMT on September 26, 2007
Back to work, see y'all at lunch

Be interesting to see the 12z global models.

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Member Since: August 17, 2005 Posts: 26 Comments: 16874
2670. decimus785
2:13 PM GMT on September 26, 2007
the high is strong,does that mean that Karen may ?stay on a wesr -westnorthwest track and not NW -NNW
2669. Eyewall911
2:12 PM GMT on September 26, 2007
Holy crap bone I have not seen the latest, I just logged back on. WOW that is a big shift left
2668. medic2luv
2:11 PM GMT on September 26, 2007
Morning all,
Is there a possibility that 98L could each TS status before crossing over FL?
Member Since: August 13, 2007 Posts: 0 Comments: 189
2667. StormJunkie
2:11 PM GMT on September 26, 2007
4me, the high is not going to allow it to make that E turn with the first trough. At least that is my current opinion. Now, the big question is does it pull it far enough N so that the high is allowed to build some on the W side of the storm as well as to the N. If that happens, Karen may just stall out until another trough comes along. Lot's of up in the air with this. Hopefully we will have a good idea in a couple of days...
Member Since: August 17, 2005 Posts: 26 Comments: 16874
2666. GoWVU
2:11 PM GMT on September 26, 2007
Bonedog that does not look good I know it can and prob will change many more times but livning here in SC I do not like it.
Member Since: September 12, 2007 Posts: 3 Comments: 380
2665. Bonedog
2:10 PM GMT on September 26, 2007
eye the models already have :(

check the ones for the 12Z run all are west of the NHC track(thick red line) :(

qa
Member Since: July 14, 2005 Posts: 14 Comments: 7418
2664. KrazyKaneLove
2:10 PM GMT on September 26, 2007
Bonedog..that is scary!
Member Since: September 7, 2007 Posts: 0 Comments: 429
2662. weathers4me
2:08 PM GMT on September 26, 2007
Why would it matter how strong the high is if the storm finds the edge of that high and scoot around it sending it out to the fishes. Is that accurate or am I missing something?
Member Since: May 24, 2007 Posts: 0 Comments: 118
2661. Eyewall911
2:07 PM GMT on September 26, 2007
Bone that is a big differance. Do you thine the models will pick up on it? I think they will and start shifting west
2660. StormJunkie
2:07 PM GMT on September 26, 2007
Morning again all

I am still amazed at how active things have gotten over the past 7 days.

One thing that is at leas somewhat encouraging is that the latest BAM models at least the medium and shallow, show Karen curving. Not out to sea per say, but they do agree on the N move. Will be a lot of wait and see over these next few days...
Member Since: August 17, 2005 Posts: 26 Comments: 16874
2659. cchsweatherman
2:07 PM GMT on September 26, 2007
Good morning. I have updated my Tropical Update page on my website if anyone wants to check out what I am thinking at this time.

Damn, Karen looks like it could be close to hurricane status based upon the latest IR and microwave images. It is looking very impressive and I expect it now to become a hurricane in 24 hours. It has begun to rapidly intensify. One concerning thing is that the newer computer models are continuing to shift left more and more every run. I do not expect the northerly turn to occur as high pressure will dictate where this beast goes.

I agree with all of you that we should have Invest 99L by the end of the day. That is a very impressive tropical low. This could be the activity that has been forecasted all season to occur and could, and I hate to say this, satisfy the wishcasters and "this season is a bust"-ers thirst for tropical activity.

We are in for a very active next few weeks. Good luck to everyone just in the case we get a landfalling storm somewhere.
Member Since: April 14, 2007 Posts: 8 Comments: 5169
2658. bayoubug
2:06 PM GMT on September 26, 2007
the trof is still digging ahead of karen looks like a ull is trying to form nnw of karen on that trof. thats probably what will pull karen north.
Member Since: July 25, 2006 Posts: 0 Comments: 283
2657. Tazmanian
2:06 PM GMT on September 26, 2007
Posted By: flzepher at 7:02 AM PDT on September 26, 2007.

What the heck is DEC785 shown on the model page for 98L ? Just a typo, the red line is normally NOGAPS


some one made that mode up and some how they put it up on the map

here is the right map

lol
Member Since: May 21, 2006 Posts: 5091 Comments: 115437

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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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