Huge Western Caribbean low bringing heavy rains; Wisconsin levee failing

By: Dr. Jeff Masters , 12:26 PM GMT on September 27, 2010

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Today, for the first day since August 20, the National Hurricane Center will not be issuing any advisories for an Atlantic named storm. Thus ends a remarkably active 36-day period that saw the formation of ten named storms, six hurricanes, and five intense hurricanes--an entire hurricane season's worth of activity, compressed into just five weeks of the six-month season. This season is not done yet, as we still have three more weeks of peak hurricane season left to go, and the Western Caribbean is looking poised to generate a tropical storm sometime in the next ten days.


Figure 1. Morning satellite image of the Western Caribbean and Central America, showing the remains of Matthew over Mexico, and a large area of disturbed weather beginning to develop over the Western Caribbean.

A wet week ahead for the Western Caribbean, Florida, and the Western Bahamas
Pressures are falling over the Western Caribbean today as a large area of low pressure develops over the region. This low is bringing heavy rains across a huge area, from the Pacific shores of El Salvador, Guatemala, and Mexico, to eastern Cuba and Haiti. All of Central America, eastern Mexico, the western 2/3 of the Caribbean, plus the Bahamas and Florida can expect sporadic periods of very heavy tropical rains over the coming week, with peak amounts of 3 - 6 inches per day possible. In the Western Caribbean, a few hundred miles east of Mexico's Yucatan Peninsula, a region of concentrated thunderstorms has built this morning, and has the potential to develop into a tropical depression by Wednesday. A large trough of low pressure over the Eastern U.S. is producing steering currents that will pull this area of disturbed weather to the north-northeast across western Cuba on Tuesday and Wednesday. The disturbance should move over Florida on Wednesday and Thursday, and over North Carolina by Thursday and Friday. All of these regions can expect very heavy rains from the disturbance, and NHC is giving a 30% chance that the disturbance will develop into a tropical depression by Wednesday. The Hurricane Hunters are on call to investigate the disturbance this afternoon, if necessary.

Once the disturbance moves out of the Caribbean, the GFS and NOGAPS models predict that the Western Caribbean will "reload" and produce another tropical disturbance capable of developing into a tropical depression late this week or early next week. The steering currents are not expected to change over the coming ten days, and Florida and western Cuba can expect to see this second disturbance potentially bring a second round of heavy rain late this week and early next week.

Levee failing in Wisconsin due to rains from Hurricane Karl's moisture
In Portage, Wisconsin, about 25 miles north of Madison, a sub-standard 120-year-old levee is failing, thanks to flood waters 3.5 feet above flood stage on the Wisconsin River. The river was swollen last week by heavy rains of up to seven inches that fell in its watershed to the northwest. The rains were generated by a plume of very moist air associated with what was Hurricane Karl. This moisture was lifted over a warm front draped over Minnesota and Wisconsin on Wednesday and Thursday. These types of rain events are called Predecessor Rain Events (PREs), because they typically precede the actual arrival of the rain shield of a tropical storm.


Figure 2. Rainfall over Minnesota and Wisconsin for the seven-day period ending 8pm EDT Sunday 9/26/10. Heavy rains to the northwest of Portage, Wisconsin led to flooding along the Wisconsin River in Portage. Image credit: NOAA.

Canadian Military responds for Hurricane Igor relief
At least twenty communities in Newfoundland, Canada are still cut off from civilization after Tuesday's rampage by Hurricane Igor. The Canadian military has sent three warships and a number of helicopters into the disaster zone to deliver food, fuel, and medical supplies to those communities still cut off. Igor killed one person and caused over $100 million in damage to the island.


Figure 3. Miniature golf anyone? A house in St. John's Newfoundland now has a very three-dimensional front yard, thanks to Hurricane Igor's winds and rain. Image credit: Zach Goudie.

I'll have an update Tuesday morning.

Jeff Masters

Wisconsin River Flooding in Wisconsin Rapids September 2010 (LadyWriter)
Jackson Street Bridge late Saturday afternoon at cresting.
Wisconsin River Flooding in Wisconsin Rapids September 2010
Wisconsin River Flooding in Wisconsin Rapids September 2010 (LadyWriter)
Taken from First Avenue while looking eastward toward Grand Avenue Bridge/Elks Club when the flooding was at its worst
Wisconsin River Flooding in Wisconsin Rapids September 2010

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Quoting afj3:
Any chance of this thing passing east of Florida entirely???
Nope
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Quoting CyclonicVoyage:


There is an upper anti-cyclone to it's west providing 10-20 kts at the moment. Not prohibitive but, slow strengthening.


So the remenants of Matthew still effecting this area then?

I would think the blob to its southeast would be in a better environment to spin up at least in proximity to other convection around 17N 82W?
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My preasure in Ruskin Fl is at 1010
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Quoting ILwthrfan:


Just a little north of 20N and a little east of 86W, definitely a spin there with a brand new thunderstorm exploding on its east side. Looks like its under a lot of shear?
I do believe I see a little shear there. My guess is about 15-KTS give or take..It is SLOWLY looking a bit more interesting...
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The entire southeastern seaboard is going to get soaked, looks like.





Member Since: August 18, 2008 Posts: 0 Comments: 884
Quoting ILwthrfan:


Just a little north of 20N and a little east of 86W, definitely a spin there with a brand new thunderstorm exploding on its east side. Looks like its under a lot of shear?




There is an upper anti-cyclone to it's west providing 10-20 kts at the moment. Not prohibitive but, slow strengthening.
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Bermuda bullseye for mini-tropical low lol (currently @ 58W 30N) Mini could be oversizing it....
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Another thing to add is if this area develops and the shear stays just to the north it will have all the evacuation in the upper levels to explode....
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Quoting hydrus:
I can see the spin now in the N.W. Caribbean....Here is RGB,,Link


Just a little north of 20N and a little east of 86W, definitely a spin there with a brand new thunderstorm exploding on its east side. Looks like its under a lot of shear?
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355. afj3
Quoting weatherboyfsu:



Heck yeah..... just a wait and see on where it exactly develops...

I guess it will be easier to predict once we have a COC....
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Quoting CyclonicVoyage:



Always happens that way for me, lol.
.....the hh are on stand-by and if need be a mission w/be tasked and they'll go in.prolly will wait until tonight or tomorrow imo
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352. 7544
looks like the plane may find a td it looking stronger at this hour
Member Since: May 6, 2007 Posts: 0 Comments: 6810
Quoting afj3:
Any chance of this thing passing east of Florida entirely???



Heck yeah..... just a wait and see on where it exactly develops...
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Quoting CyclonicVoyage:
TPC thoughts @ 72hrs.



That's very fast for a 30% blob.......................
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Quoting Buhdog:
What invest number is next? SFWMD has a model plot as of 11:06 am bulls eye PT Charlotte
Link

listed as storm 50


That is the last forecast from the UKMET Office

NEW TROPICAL STORM FORECAST TO DEVELOP AFTER 48 HOURS
FORECAST POSITION AT T+ 48 : 22.2N 84.2W

VERIFYING TIME POSITION STRENGTH TENDENCY
-------------- -------- -------- --------
00UTC 29.09.2010 22.2N 84.2W
12UTC 29.09.2010 24.3N 83.0W WEAK INTENSIFYING SLIGHTLY
00UTC 30.09.2010 26.7N 82.2W WEAK INTENSIFYING SLIGHTLY
12UTC 30.09.2010 BELOW TROPICAL STORM STRENGTH
Member Since: September 23, 2005 Posts: 14 Comments: 11153
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Barometer fell this morning to 1007 (Cayman Brac), but now steady. Raining. 8kt wind, down from 15 earlier.

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346. afj3
Any chance of this thing passing east of Florida entirely???
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Geeezzzzz..... I just noticed that they have our start dates on here.... wow....
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Quoting FLdewey:
Well I see we've jumped in feet first today... might as well start the week off right I guess.
I can see the spin now in the N.W. Caribbean....Here is RGB,,Link
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343. HCW
Quoting Jeff9641:
I wouldn't be surprised if C FL see quite a bit of severe wx later this afternoon with so much shear in place.


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Quoting CyclonicVoyage:


Potential is there.


if it develops a tight closed low by tonight, it has that likelyhood, we'll see..
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Quoting hydrus:
I am wondering if we will see multiple centers again. These "monsoonal" lows seem to generate plenty of them.

True that. Trying to predict tropical cyclogenesis if the "fun" (hardest) part, just ahead of intensity.

We could really use the rain on the Space Coast, but I know my old roof could never withstand a major. Definitely have mixed feelings about the coming days.
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1445Z 9:45AM CDT/ 10:45AM EDT AVN Satellite shot of the Western Atlantic, our AOI is blossoming nicely:
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Quoting weatherboyfsu:
Im thinking that this area is going to explode.... time will tell


Potential is there.
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Im thinking that this area is going to explode.... time will tell
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Quoting Buhdog:
What invest number is next? SFWMD has a model plot as of 11:06 am bulls eye PT Charlotte
Link

listed as storm 50


Next invest up will be 96L...
Member Since: November 8, 2009 Posts: 4 Comments: 13525
As usual.... anything is possible but it looks to me that matthew is going to continue to drift west.... the trough is already by...
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What invest number is next? SFWMD has a model plot as of 11:06 am bulls eye PT Charlotte
Link

listed as storm 50
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Quoting tacoman:
all im saying is dont write off matthew yet it mat come back to bite you in the ass...recon should have a flight ready to check matthew when it emerges off the yucatan...


+1 --- I agree
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TPC thoughts @ 72hrs.

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The blob is punny today. Oh well, almost lunch time. Off to the Golden Arches.
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Quoting guygee:
If I had to guess where the surface circulation is trying to form from the sat loops, I would say roughly 84W, 21N, not under the deepest convection. Pretty sure nothing closed off yet.
I am wondering if we will see multiple centers again. These "monsoonal" lows seem to generate plenty of them.
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Our new low looks HEALTHY! From the SFWMD

8 am
South Florida Water Management District
Tropical Conditions Report
8:08AM Monday, September 27, 2010 (gws)

Current Conditions:

LOCAL STORM/HURRICANE WATCHES/WARNINGS: None
Tropical Storm Force or Greater Winds Within 48 Hours: No

DISCUSSION:

Disorganized clouds and thunderstorms over the northwestern Caribbean are associated with a broad area of low pressure. Little movement is expected today, but slow development is probable over the next couple of days. Regardless of any development, deep tropical moisture will likely move northward through the peninsula and combine with a non-tropical system over the southeast US to generate heavy rains initially south and east of the Lake beginning as early as late tomorrow.

A small, slow moving tropical low is located about 725 miles west southwest of the Cape Verde Islands. Any development is expected to be slow to occur.

In light of what ive read today on the blog - a request - Link
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Anybody seen the Quikscat on todays runs.... Whatever that things called that shows the winds over that area? I dont see shear in this area.... I would be surprised if the recon cancels....
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If I had to guess where the surface circulation is trying to form from the sat loops, I would say roughly 84W, 21N, not under the deepest convection. Pretty sure nothing closed off yet.
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IMO it looks like the two AOIs are going to merge before too long and make one Invest. Maybe that's what they're waiting for, see which one dominates.

Ooops, may have opened this up for another round of rediculous... Be adults, folks!
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23kts in a couple places far from the COC.

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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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