Two Caribbean disturbances to watch

By: Dr. Jeff Masters , 2:14 PM GMT on October 14, 2007

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A persistent low pressure system extending from the Central American nations of Guatemala, El Salvador, and Belize northeastward over Jamaica, the Cayman Islands, Cuba, Haiti, and the Bahamas continues to dump heavy rain over much of the region. Heavy rains of at least five inches in northern Haiti triggered floods that killed at least 47 people Friday and left over 20,000 homeless. The flooding was worst in Cabaret, Haiti, near the north coast. No new rains fell Saturday, and further flooding is not expected. Heavy rain will continue to affect central and western Cuba today.

Connected to this deadly rain-making low pressure system is the large "sleeping giant" low pressure system that has been spinning over the Yucatan region the past week. This low continues to spin in the extreme southwest corner of the Western Caribbean, where Belize, Guatemala, and Honduras meet. Last night's QuikSCAT pass showed an elongated, poorly formed circulation, which will make development into a tropical depression today unlikely. None of the models develop the system. It is forecast to move northwest over the Yucatan Peninsula on Monday, emerging into the Gulf of Mexico on Tuesday. At that point, a trough of low pressure may be able to pull it towards a landfall near the Texas/Mexico border by Thursday. The trough may not be strong enough to turn the storm northwards, though, and it may come ashore in Mainland Mexico near Veracruz.

Even if the sleeping giant does not intensify into a tropical depression, this low could be a dangerous storm for Central America, bringing heavy rains of up to five inches to Belize, Guatemala, northwest Honduras, and Mexico's Yucatan over the the next three days. These heavy rains may also affect the Pacific coast regions of El Salvador, Mexico, and Guatemala, as the counter-clockwise flow of air around the low sucks in air from the Pacific Ocean.


Figure 1. Satellite estimated rainfall for the 24 hours ending at 2 am EDT Sunday.

New Caribbean disturbance
A tropical wave (98L) in the southern Caribbean is headed west towards Nicaragua and Honduras. This morning's QuikSCAT pass showed a fairly well-formed circulation. The system is under about 25 knots of wind shear, so any development today will be slow. Shear is expected to drop to 15 knots by Monday morning, which may allow for a better chance of development.

I'll have an update Monday.

Jeff Masters

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709. NEwxguy
1:53 PM GMT on October 15, 2007
bonedog,that was where TD15 was,it was absorbed into that system.
Member Since: September 6, 2007 Posts: 873 Comments: 15568
708. IKE
1:45 PM GMT on October 15, 2007
NEW BLOG!
Member Since: June 9, 2005 Posts: 23 Comments: 37858
707. Bonedog
1:39 PM GMT on October 15, 2007
Lenny was the strongest Atlantic hurricane ever recorded in November, and quite unusual in that it moved west-to-east across the Caribbean.It was the first time such a trajectory had been seen in 113 years of hurricane observations in the Atlantic/Caribbean basin


that is odd!!
Member Since: July 14, 2005 Posts: 14 Comments: 7418
706. Floodman
1:39 PM GMT on October 15, 2007
685. IKE 12:58 PM GMT on October 15, 2007
40-60 knots of shear in the central and northern GOM...and the east coast.....

Link




Yep, but 48-60 hours out there's 0-5knts across the GOMEX...
Member Since: August 2, 2006 Posts: 10 Comments: 9922
705. Bonedog
1:35 PM GMT on October 15, 2007
ecf I watched that all weekend the midwest severe. Actually though at this time of year it is normal to have severe weather because of the fact of the diffrences in the airmasses. Warm moist gulf air and cold polar air, perfect ingrediants for thunderstorms.

The spc has issued a outlook watch box for the ohio valley because of the front moving through

DISCUSSION...
MODELS HAVE COME INTO ENOUGH AGREEMENT -- AT LEAST FOR DAY 4 /THU.
OCT. 18/ -- THAT SUFFICIENT CONFIDENCE EXISTS TO INTRODUCE A SEVERE
AREA CENTERED ON THE OH/TN VALLEYS. SOME DEGREE OF INTENSITY/TIMING
DIFFERENCES REMAIN WITH THE MAIN FEATURES AT THE SURFACE AND ALOFT
DAY 4. HOWEVER...IT APPEARS THAT AMPLE INSTABILITY WILL DEVELOP BY
AFTERNOON ACROSS THIS AREA AHEAD OF AN APPROACHING COLD FRONT AND
ASSOCIATED UPPER TROUGH TO ALLOW STORM DEVELOPMENT TO OCCUR. MODELS
FORECAST STRONG SHEAR /50 TO 60 KT SWLY FLOW AT MID LEVELS/...WHICH
SHOULD SUPPORT ORGANIZED/SEVERE STORMS.
Member Since: July 14, 2005 Posts: 14 Comments: 7418
703. Bonedog
1:31 PM GMT on October 15, 2007
nevermind. I read the highseas forcast and they mention it as just a Low. I am just wondering because its very close to the last advisory position of TD15 though.
Member Since: July 14, 2005 Posts: 14 Comments: 7418
702. ecflawthr
1:31 PM GMT on October 15, 2007
how many on here pay attention to severe weather. there was quite a bit this weekend. hail fell all over the place with reports of 2 inch and larger in some places. the scary part is this could be just the beginning as a lot of forecasters are predicting that by the end of the week we could see major outbreak in severe weather that is vary unusual for this time of year. looks like this will be the weather to watch and not the tropics.
Member Since: September 4, 2006 Posts: 1 Comments: 201
701. hurricane23
1:25 PM GMT on October 15, 2007
STL i meant landfall wise on a significant impact from a major cane.Its still possible to have 1-2 more sheared tropical cyclones.
Member Since: May 14, 2006 Posts: 8 Comments: 13621
700. Bonedog
1:24 PM GMT on October 15, 2007
any answer to my 689 post?
Member Since: July 14, 2005 Posts: 14 Comments: 7418
697. Bonedog
1:18 PM GMT on October 15, 2007
I know not tropical related but there was just a 6.8 mag earthquake in New Zeland. Looking at the shake maps there could be moderate/heavy damage to the region



Member Since: July 14, 2005 Posts: 14 Comments: 7418
695. hurricane23
1:16 PM GMT on October 15, 2007
685. IKE 08:58 EDT le 15 octobre 2007
40-60 knots of shear in the central and northern GOM...and the east coast.....

Link

If that does not spell the end is near then i dont know what will...The rest of the tropical atlantic is unfavorable for development.
Member Since: May 14, 2006 Posts: 8 Comments: 13621
694. SEFL
1:15 PM GMT on October 15, 2007
!
693. Bonedog
1:12 PM GMT on October 15, 2007
Yea NE appears to be heading that way
Member Since: July 14, 2005 Posts: 14 Comments: 7418
692. NEwxguy
1:12 PM GMT on October 15, 2007
read your blog update bonedog,sounds like its going to be an interesting winter.
Member Since: September 6, 2007 Posts: 873 Comments: 15568
691. FloridaRick
1:09 PM GMT on October 15, 2007
Is there a reason the last couple of invests on the WU tropics page don't show up. If you click on the Models diagram, it shows the old invests that carried the same id number. The link shows the correct storm, but when clicked it goes to invests from September. Anyone on here know who to contact to get the correct graphic posted?
Member Since: July 27, 2005 Posts: 0 Comments: 18
690. weathermanwannabe
1:09 PM GMT on October 15, 2007
Morning All...Will be lurking today but things seem very quiet in the tropics (as they should be this time of the year); wondering what Dr. M's 2nd half of October outlook will look like....Pretty quiet also I would think......
Member Since: August 8, 2006 Posts: 0 Comments: 8712
689. Bonedog
1:09 PM GMT on October 15, 2007
Is this old TS 15 or a new system? looks impressive even on QS

Member Since: July 14, 2005 Posts: 14 Comments: 7418
687. OSUWXGUY
1:06 PM GMT on October 15, 2007
cpaman-

Gray's "salt water" theory is very relevant to tropical cyclone forecasting and SSTs in the tropical Atlantic. It has to do with the Therohaline Cycle in the Atlantic Basin...and I will say that it is likely responsible for most (if not all) of the recent increase in hurricanes since 1995. However, this circulation does NOT explain the increase in GLOBAL mean temperatures associated with Global Warming. Gray is just flat wrong in drawing a connection there.
686. Bonedog
12:58 PM GMT on October 15, 2007
I have mine organized by weather type Baha.

Severe, Tropical, Winter, Nor'Easter.

I also have general weather ones

NOAA, SPC, HPC, Education, Models, Forcasting

then about a dozen others for more specific things such as sat images and loops

Besides having a ton of RAM I also have 4 screens running at one time coupling two hard drives LOL. My boss always laughs when he walks by my desk. One screen for my job and three for weather or should I say one for work, one for the blog and 2 for weather.
Member Since: July 14, 2005 Posts: 14 Comments: 7418
685. IKE
12:58 PM GMT on October 15, 2007
40-60 knots of shear in the central and northern GOM...and the east coast.....

Link
Member Since: June 9, 2005 Posts: 23 Comments: 37858
684. weathers4me
12:52 PM GMT on October 15, 2007
Nothing on the horizon according to the models.


Link
Member Since: May 24, 2007 Posts: 0 Comments: 118
683. BajaALemt
12:52 PM GMT on October 15, 2007
I had an idea a couple of weeks ago to set up folders for areas of interest...then delete them as they go poof. I have YET to actually sit down and DO this. *laffs*
Member Since: September 25, 2007 Posts: 53 Comments: 8533
682. Bonedog
12:50 PM GMT on October 15, 2007
morning JFV
Member Since: July 14, 2005 Posts: 14 Comments: 7418
680. BajaALemt
12:47 PM GMT on October 15, 2007
Mornin JFV
Member Since: September 25, 2007 Posts: 53 Comments: 8533
678. BajaALemt
12:45 PM GMT on October 15, 2007
Folders!! Ha! Now THERE'S a novel idea *laughing* I really have to sit down one of these days and ORGANIZE my links!! They've really gotten out of hand!!
Member Since: September 25, 2007 Posts: 53 Comments: 8533
677. Bonedog
12:43 PM GMT on October 15, 2007
looks familiar might have looked at it long time ago LOL I have so many links I probably have it in one of the folders
Member Since: July 14, 2005 Posts: 14 Comments: 7418
676. BajaALemt
12:41 PM GMT on October 15, 2007
Most welcome. I was thinking to myself...you HAVE TO have SEEN this!! lol
Member Since: September 25, 2007 Posts: 53 Comments: 8533
675. Bonedog
12:40 PM GMT on October 15, 2007
thanks Baha
Member Since: July 14, 2005 Posts: 14 Comments: 7418
674. BajaALemt
12:39 PM GMT on October 15, 2007
Link

NWS's site
Member Since: September 25, 2007 Posts: 53 Comments: 8533
673. Bonedog
12:35 PM GMT on October 15, 2007
have a link for that one Baha? I have not heard of that site
Member Since: July 14, 2005 Posts: 14 Comments: 7418
672. BajaALemt
12:32 PM GMT on October 15, 2007
Jetstream is another 'general' that's pretty good
Member Since: September 25, 2007 Posts: 53 Comments: 8533
671. StormHype
12:29 PM GMT on October 15, 2007
I don't expect much out of 98L or 99L anywhere in the CONUS, or for that matter, anywhere at all. Maybe some rain eventually in CONUS but that might even dry up before whatever is left makes it that far north.

Dry and cool here is SW FL this am. Like California weather. :)
Member Since: May 31, 2007 Posts: 0 Comments: 1200
670. BajaALemt
12:28 PM GMT on October 15, 2007
I have to agree. It was ALSO written in easily understood language. I appreciate the links you guys post and listening to your ideas about what's going on. I told Storm the other day, that I often sit with his blogs and fifty bazillion pages open (good thing I have 2 gigs of ram!! lol) trying to SEE what he's saying. I do that with alot of you guys. LOL
Member Since: September 25, 2007 Posts: 53 Comments: 8533
669. Bonedog
12:24 PM GMT on October 15, 2007
ww2010 is what I started with LOL :) Both are excellent learning sites and should be reccdomended to anyone wanting to learn weather. ww2010 is a great beginner course for all kinds of weather where as weather prediction.com is great for the begginer forcaster or the slightly more advanced beginner that has a some knowledge of weather terminology. Not that it is required but found it helps.
Member Since: July 14, 2005 Posts: 14 Comments: 7418
668. BajaALemt
12:21 PM GMT on October 15, 2007
Link saved, Bone...thanks..I'll have to check that out after work (I'm a reader, as well)
Member Since: September 25, 2007 Posts: 53 Comments: 8533
667. BajaALemt
12:19 PM GMT on October 15, 2007
Bone? As a beginner, I found WW2010 ( http://ww2010.atmos.uiuc.edu/(Gh)/home.rxml ) helpful (among a few others)
Member Since: September 25, 2007 Posts: 53 Comments: 8533
666. BajaALemt
12:14 PM GMT on October 15, 2007
Looks like the dry air's being pulled out of the way enough to allow some of that moisture to move up into the GOM

Link
Member Since: September 25, 2007 Posts: 53 Comments: 8533
665. Bonedog
12:09 PM GMT on October 15, 2007
your all welcome. I find I spend hours at a time reading on that website. Very easy reading for begginers and gets into alot of what is talked about here. I have learned loads there.

Check out the top of the page where there is a 10 part series on weather forcasting. You will learn the diffrence between wishcasters and folks that might be a little ahead of the model runs and why they are.
Member Since: July 14, 2005 Posts: 14 Comments: 7418
664. BajaALemt
12:06 PM GMT on October 15, 2007
*Thanks* even
Member Since: September 25, 2007 Posts: 53 Comments: 8533
663. BajaALemt
12:06 PM GMT on October 15, 2007
That's bone...that's one I didnt have. Oh goody..a new toy (laffs)
Member Since: September 25, 2007 Posts: 53 Comments: 8533
662. PensacolaDoug
12:04 PM GMT on October 15, 2007
Good explanation. Bone. Thanx.
Member Since: July 25, 2006 Posts: 0 Comments: 549
661. Bonedog
12:03 PM GMT on October 15, 2007
no problem. Its from a great weather website dedicated to learning all about weather and forcasting

Link
Member Since: July 14, 2005 Posts: 14 Comments: 7418
660. BajaALemt
12:00 PM GMT on October 15, 2007
Nice explanationa and graphic, Bone.
Thanks

Morning folks
Member Since: September 25, 2007 Posts: 53 Comments: 8533
659. Bonedog
11:53 AM GMT on October 15, 2007
The thermal low (also called a heat low) occurs due to intense daytime heating over a region. Typically the synoptic pattern will be benign and the location will be in a dry land climate. Solar radiation strikes the earth's surface and warms the troposphere from below. Dry lands such as those found in semi-arid and arid regions warm up rapidly under sunlight since there is little moisture from the soil or plants to produce evaporational cooling. The very hot air in the boundary layer is inclined to rise since warming air becomes less dense and more buoyant. When air rises over a region the surface pressure will decrease just as pressure would decrease from lifting from a front or mid-latitude cyclone. Typically the dewpoint and relative humidity of the heated air in the boundary layer are low. This reduces the amount of precipitation that occurs from thermal lows. Isolated storms or no storms at all due to a capping inversion are common. Stability aloft reduces the vertical depth of a thermal low. The thermal low will be strongest at the surface but will weaken with height since the air is rising at the greatest rate closer to the earth's surface. A thermal low will tend to stay in the same source region it developed thus it will not transverse great distances like a mid-latitude cyclone will do. The diagram below shows a thermal low in a vertical cross section:

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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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