Disturbance 95L over South Florida bringing heavy rains

By: Dr. Jeff Masters , 1:27 PM GMT on June 29, 2007

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Clouds and showers associated with a weak low pressure system over South Florida have increased markedly this morning. NHC has designated this system "95L". Long range radar from Melbourne, Florida shows an expanding area of echoes, but there are no signs of any organization or spin. With wind shear remaining high at 20-30 knots, I'm not expecting any development of this disturbance today. Some of the computer models are forecasting that wind shear will slowly drop the next three days, so we'll have to keep a closer eye on 95L over the weekend. The system could bring heavy rains to South Florida and the northwestern Bahama Islands the next two or three days. A Hurricane Hunter airplane is on call to investigate the system Sunday at 2pm, if necessary.

A trough of low pressure is scheduled to push off the U.S. Southeast Coast on Monday, and will probably sweep 95L out to sea in front of it. There is a chance something could develop along the remains of a cold front the trough leaves behind over the Gulf Stream. However, none of the reliable computer models are forecasting any tropical storm formation over the coming week.


Figure 1. Preliminary model tracks for the disturbance near South Florida.

One other area to watch is the region just north of Panama in the Southwest Caribbean. Wind shear values are forecast to drop below 5 knots there by Sunday.

Wind shear decline expected
The jet stream usually divides itself into two branches this time of year--a strong jet whose average position is near the U.S.-Canadian border (the polar jet), and a weaker branch whose average position is over the Gulf of Mexico (the subtropical jet). Both of these branches of the jet stream bring high upper level winds (and thus high wind shear) over the Atlantic Ocean. All of the computer models are forecasting that the subtropical jet will weaken substantially over the next ten days, bringing much lower than average wind shear to the tropical Atlantic. It is normal to see the subtropical jet weaken in the summer, but it usually happens a month later than this--in August. The expected early weakening of the subtropical jet should give us an above-average risk of a July tropical storm. I'll have a full analysis of the possibilities on Monday, when I post my bi-monthly 2-week outlook.

Jeff Masters

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771. WPBHurricane05
11:26 AM GMT on June 30, 2007
Observed at: Albany, Georgia
Elevation: 197 ft
73 F
Clear
Humidity: 90%
Dew Point: 70 F
Wind: Calm
Pressure: 30.02 in (Rising)
Visibility: 9.0 miles
UV: 0 out of 16
Clouds: Clear -(Above Ground Level)

No clouds and pressure is rising in Albany, Georgia which went through the circle thing.
Member Since: July 31, 2006 Posts: 56 Comments: 8112
770. FloridaScuba
11:22 AM GMT on June 30, 2007
thank wpb for that gif. i saved it. totally wierd looking, i've never seen something like that... a perfect expanding circle. does that happen alot? "ground clutter"?
769. kmanislander
11:19 AM GMT on June 30, 2007
Baranquilla Colombia has wnw winds @5 mph so there may be a weak low in that blob
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768. WPBHurricane05
11:18 AM GMT on June 30, 2007
Here is another view Link
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767. WPBHurricane05
11:17 AM GMT on June 30, 2007
It looks like ground clutter Florida.
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766. FloridaScuba
11:13 AM GMT on June 30, 2007
Link

morning all. i don't know if anyone else can see this but it's an animated regional radar map. above tallahassee, in SW georgia, there is a wierd expanding perfect circle. looks different that a storm. like someone showed once more like a volcanic eruption. can anyone else see that ?
765. kmanislander
11:10 AM GMT on June 30, 2007
good morning all

The area just offshore Colombia has high pressure directly overhead and only 5 to 10 knots of shear. It would need to pull more to the wnw away from land to have a shot at developing IMO

Link
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764. WPBHurricane05
11:04 AM GMT on June 30, 2007
It needs to have a low pressure center.
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762. WPBHurricane05
10:40 AM GMT on June 30, 2007
Watch the Caribbean. Link
Here are the steering currents. Link
This system has a chance to make it into the Gulf.
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761. spiceymonster
10:31 AM GMT on June 30, 2007
So basically if it can get away from land then we might have something on our hands.
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759. underthunder
10:16 AM GMT on June 30, 2007
bless yer heart tampa...we finally have been blessed with some of the good stuff the past 2 days...a total of an inch..not much...but we consider it a blessing...we here are praying for a tropical depression...it's the only thing that will save us...
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758. spiceymonster
10:13 AM GMT on June 30, 2007
Does the blob N. of Panama have any chance of doing anything except going into the Eastern Pac.
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757. TampaWeatherBuff
10:05 AM GMT on June 30, 2007
The last three days here just south of Brandon, FL, they've been promising 60-70% chance of heavy rain, but we've seen nary a drop of the stuff.

Very disappointing.
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755. StoryOfTheCane
8:48 AM GMT on June 30, 2007
754. StoryOfTheCane
8:46 AM GMT on June 30, 2007
753. 0741
7:13 AM GMT on June 30, 2007
their area near bermuda that need to be watch doing weekend but it look like going out to sea 27.8 57.0 Link
752. BahaHurican
5:52 AM GMT on June 30, 2007
I'm out, folks. My computer seems to be double-posting me, so I'm heading out before I actually start seeing double too . . .

G'night!
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751. stormybil
5:45 AM GMT on June 30, 2007
around 75w 10 north if that big blob gets in the caribiean we might have somthing to watch latter on today as they at the nhc stay tuned .!
750. brazocane
5:44 AM GMT on June 30, 2007
Okay this clears it up:

"The heaviest rainfall to occur in 24 hours was measured in Yankeetown during Hurricane Easy (1950), 38.70 inches/983 mm. This is also the highest known point storm total maximum related to any tropical cyclone which has impacted Florida,[15] and by itself would be the highest known rainfall total for any month from any location within Florida. This rainfall amount remained the national 24-hour rainfall record until Tropical Storm Claudette (1979).[16] Heavy rainfall events have fallen due to stalled fronts near the state as well, and occur during the March through May and October through November timeframe"
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749. Boatofacar
5:44 AM GMT on June 30, 2007
Its kinda hard to argue with the data on that site....
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748. BahaHurican
5:42 AM GMT on June 30, 2007
5 September 1950, Yankeetown, Florida: Hurricane Easy drops the greatest 24-hour rainfall in US weather records. The storm deluges Yankeetown on the upper west coast of Florida, with 38.7 inches (983 mm) of rain.

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747. BahaHurican
5:39 AM GMT on June 30, 2007
United States' heaviest 24-hour rainfall -- On this date (July 25) in 1979 the greatest single 24-hour rainstorm in the United States began. In a 24-hour period from the 25th into the 26th, 43 inches of rain fell at Alvin, Texas.(07/25/99)

This was from Tropical Storm Claudette.
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746. brazocane
5:36 AM GMT on June 30, 2007
Check this site Jedkins

Link

I think it would be considered reputable wouldnt you.
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745. brazocane
5:30 AM GMT on June 30, 2007
"On July 25, 1979 Tropical Storm Claudette stalled over Alvin and inundated the region with 45 inches in 42 hours. That total included 43 inches in 24 hours, the maximum 24-hour rainfall in US history."

That is what I found on Wikipedia and other sites still say Alvin holds the record.

But I was thinking some town in Florida got like 48 in. must have been Yankeetown, but when did that happen and what hurricane.

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744. Jedkins
5:18 AM GMT on June 30, 2007
Posted By: BahaHurican at 5:12 AM GMT on June 30, 2007.

Found this:

United States' heaviest 24-hour rainfall -- On this date (July 25) in 1979 the greatest single 24-hour rainstorm in the United States began. In a 24-hour period from the 25th into the 26th, 43 inches of rain fell at Alvin, Texas.(07/25/99)


Where is the source from?
743. Jedkins
5:15 AM GMT on June 30, 2007
Posted By: HopquickSteve at 2:37 AM GMT on June 30, 2007.



Man...we're so completely wet. Notice the max rainfall on the top corner (32.4 inches?!)




See that image you posted that says max rain 32 inches, (and I want to point out now so you dont get confused).



Thats ground clutter thats built up on the storm total.

You'll see that with radar sites that have almost no rain or none at all and it will say max rain 20 inches or 32 like that said.


Still though, between 4 and 8 inches has fallen here with a few spots locally up to 12. Thats disturbing. Because grounds were aready very saturated at that time before this moved in. This is brtual death causing rainfall.


742. BahaHurican
5:12 AM GMT on June 30, 2007
Found this:

United States' heaviest 24-hour rainfall -- On this date (July 25) in 1979 the greatest single 24-hour rainstorm in the United States began. In a 24-hour period from the 25th into the 26th, 43 inches of rain fell at Alvin, Texas.(07/25/99)
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741. Jedkins
5:09 AM GMT on June 30, 2007
Posted By: HopquickSteve at 3:01 AM GMT on June 30, 2007.

I know I've been posting a lot of my local radar... my apologies for anyone offended.

But does the 30+ in of rain and the cut off low over texas, ok, and ks, get fed by the lack of shear in the GoM?





They haven't had 30 plus inches from this low pressure area. Don't exaggerate. The entire section where that rain fell would be a huge shallow lake for a few months if that much rain fell over those areas.


Yes rain has been horrible in those areas, and its record flooding and incredible heavy rains for that location have fallen. But Texas is still a landmass LOL.


Florida could haldle such rain, having sandy soil, surrounded by water, lots of wetlands and rivers.


But the great plains couldn't handle such rain without the end of area effect as we know it if it rained that much there.
740. Jedkins
5:02 AM GMT on June 30, 2007
Posted By: brazocane at 4:04 AM GMT on June 30, 2007.

Next town over from me in Alvin Texas had held the record for something like 42 inches in 24 hours back in the late 70's. I think it was recently broken.



Are you talking about nationwide? Cause that aint the record. And I don't think any 42 inch rain record in 24 hours was broken recently. I would have defintely remembered.



Yankeetown Florida received 48 inches in 24 hours from a hurricane that came in and stalled over Florida, thr deep intense eyewall convection remained in tact in the eywall. As a result, being it was the eyewall of a hurricane and it wasn't going anywhere, it dropped a water nuke over yankeetown Florida and the surrounding cities.


739. Jedkins
4:55 AM GMT on June 30, 2007
We had 12 to 15 inches of rain across the area here in 3 to 4 hours last year on a crazy day. Forget the daily total, but we picked up a couple more inches before the day was done.


I live in pinnelas and drainage is very good. Flooding was relatively minor even from that deluge. And we weren't in a drought either at that time. Was about normal preceding it.

738. SavannahStorm
4:30 AM GMT on June 30, 2007
Here in Savannah, we get 2 inches of rain and parts of the city flood. While downtown Savannah was built on a 40-foot bluff, the rest of the city was built on either cypress swamp, salt marsh, or reclaimed rice patties. That is compounded by the fact that we have the 2nd highest tides on the east coast (after the Bay of Fundy) and when we get a quick, hard shower during high tide the storm water systems can't handle it.

Even though we have a huge rain deficit, a little over a week ago we got 3 inches or so of rain and neighborhoods flooded. I only pray that we never get a major hurricane here during my lifetime or it'll make Katrina look like a spring shower.
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737. weatherblog
4:18 AM GMT on June 30, 2007
Posted By: Hurricaniac at 4:04 AM GMT on June 30, 2007.

Looks like some weather headed this way. LOL.


Lucky!
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736. Hurricaniac
4:04 AM GMT on June 30, 2007
Looks like some weather headed this way. LOL.
735. brazocane
4:04 AM GMT on June 30, 2007
Next town over from me in Alvin Texas had held the record for something like 42 inches in 24 hours back in the late 70's. I think it was recently broken.
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730. cajngranny
3:46 AM GMT on June 30, 2007
Pat, you have been posting links to the Gulf. Kori, you just mentioned the clouds that came of the Yucatan today. Has anyone noticed the tiny blob in the Bay of Campeche? It has just sat there most of the day, only during the past 3or so hours starting to move north noticably. It is on the western edge of the 30 shear. For some reason, it caught my eye this morning.
729. KoritheMan
3:35 AM GMT on June 30, 2007
Before anyone says the thunderstorms by the Yucatan in the southern Gulf could refire overnight with the diurnal max, that may be true, but if 30 knot shear is still there, it won't last until the diurnal max. Also, even if convection did refire, the system does not have any turning whatsoever. The entire cloud system itself is moving north, with convection being sheared off to the northeast. If the cloud system continues to move north without dying, though, then we may have to watch it, especially if it meanders.
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728. KoritheMan
3:33 AM GMT on June 30, 2007
TCW, where do you get that shear is high in the Gulf? 20 knots in the eastern Gulf is moderate, not high, and will not completely "destroy" 95L's low if it moves in there....

Elsewhere, shear is 5-10 knots, except for one small area in the southern Gulf above the Yucatan, where shear is 30 knots. That's what's tearing the thunderstorms that moved into the Gulf a few hours ago apart.
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727. Chicklit
3:29 AM GMT on June 30, 2007
If 30 inches of rain fell here, we would have some pretty gruesom stories to tell. If anyone survived it................
My son lives out there. You should see the size and number of the concrete canals.
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726. tornadofan
3:25 AM GMT on June 30, 2007
It seems that South Alabama is built to handle heavy rain. We get T-storms all the time dumping 3-4 inches of rain, with little or no flooding it seems.
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725. pottery2
3:22 AM GMT on June 30, 2007
An estimated 25,000 poeple died in a rainstorm in coastal Venezuela a couple years ago. Estimated rainfall was 12 inches in 6 hrs. Entire villages washed into the sea. 36 inches would be 20 times worse than that.........
724. tornadofan
3:14 AM GMT on June 30, 2007
Hurricane Danny rained over 36 inches on to Dauphin Island, Alabama in 1997.
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723. sporteguy03
3:11 AM GMT on June 30, 2007
Keep an eye on 10N 75W interesting convection about to leave South American Coast in low shear has some warm waters ahead.
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722. pottery2
3:10 AM GMT on June 30, 2007
If 30 inches of rain fell here, we would have some pretty gruesom stories to tell. If anyone survived it................
721. Ivansurvivr
3:08 AM GMT on June 30, 2007
Don't hurricanes cause upwelling which brings cold water from very deep and mixes it with warmer water closer to the surface? My fear is with little tropical activity except for Bermuda and the fish in the east Atlanic, the water below the surface may be the real problem
Look at what the loop curent (deep warm water) does to storms in the gulf. I hope the lack of storms last year didn't turn the west atlantic, Carribean and rest of the gulf into 1 big loop current.

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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.