Gulf of Mexico low growing more organized
The large extratropical storm that has been drenching Florida over the past few days continues to pour rain on the state as it treks slowly west-northwestward over the Gulf of Mexico. Rainfall amounts as high as 23.75 inches have been measured in Northern Florida at the Flagler County Fairgrounds over the past four days, and Daytona Beach has seen over 14 inches, forcing closure of numerous roads. Another 1 - 3 inches are expected in Northeast Florida today from the storm, along with beach erosion, 7 - 10 foot waves, and tides 2 - 3 feet above normal. The bad weather in Northeast Florida should gradually subside Friday and the rains should diminish substantially on Saturday, when the center of the storm is expected to move ashore over Louisiana.
Figure 1. Storm total rainfall estimated from the Melbourne radar.
Latest visible satellite loops show that the circulation of the low has grown more circular and better defined, and heavy thunderstorm activity is starting to build off the Gulf Coast of Florida on the low's east side. These thunderstorms are beginning to form spiral bands characteristic of a developing tropical depression. Water vapor satellite imagery shows that the low is moving into an area of dry continental air, though, and this dry air will slow development. Wind shear is about 20 knots, which is low enough to allow development. While none of the computer models develop the storm, they generally predict the storm should move northwestwards towards Louisiana over the next two days, and the shear is lower to the north. The low is currently over Sea Surface Temperatures (SSTs) of about 27°C in the Loop Current, which is about 1°C (1.8°F) warmer than average. SSTs of at least 26°C are typically needed to support a tropical storm, so I expect the low will continue to develop through Friday. By Friday night, the low will be approaching the Louisiana coast, and SSTs will cool to 26°C. Still, with wind shear expected to drop, this low has a medium (30 - 50%) chance of developing into a subtropical or tropical depression before its expected landfall Saturday over Louisiana. Since there will be strong winds from the west creating wind shear over the storm, plus dry air to the storm's west, most of the heavy rain should be confined to the east of the storm's center, along a stretch of coast from New Orleans to Pensacola. Rainfall totals of 3 - 6 inches can be expected.
Figure 2. Latest satellite image of the Gulf of Mexico storm.
I'll have an update Friday morning, or sooner if NHC declares this storm an area of interest (an "Invest").
Jeff Masters
Taken last night with a 16mm lense. Enjoy
Mark
www.shockpic.smugmug.com
Reader Comments
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Maybe I should have specified anthro =}
Just thought I'd point it out. I thought it was funny =P How bout that explosion of convection west of Haiti? Have to keep an eye on it, depending on it's direction it may can get to <25 knots shear, though I expect it will die down soon. another thing: Is the ULL pulling north away from the surface circulation?
From Haiti
It's raining since last saturday on the south of country. When I make a look on the satellite I can the system (Jamaica-Haiti-Cuba) is literaly explode. I would like to know if they are any chance for this system to develop on a named storm. If not how we can explain this explosion of energy... ?
Thank you every one.
Its all from the Low in the GOM. I don't see anything developing....We just need this LOW to move! You are stuck in a band that is not moving. This is very character of SubTropical like systems where often miles from the COC has problems.
Shear isn't horrible, its about 20 kts.
SST's are acceptable.
Subtropical Storms have a looser range. I doubt this will ever be fully tropical.
NEWS RELEASE
*** FLASH FLOOD WARNING REMAINS IN EFFECT FOR ALL PARISHES ***
The Meteorological Service has continued the Flash Flood Warning for low-lying and flood-prone areas of all parishes until 5:00 p.m. tomorrow.
This Warning means that flooding has been reported or will occur shortly.
Satellite imagery indicates a broad Area of Low Pressure has developed across the central Caribbean extending over Jamaica. The island continued to experience periods of moderate to heavy showers and thunderstorms throughout today especially over eastern and central parishes.
The forecast is for limited movement of this system; therefore, the general instability should persist through tonight into tomorrow; resulting in periods of showers, across most parishes. Further flash flooding of low-lying and a flood- prone areas is therefore expected.
Fishers and other marine interests are advised to exercise caution in areas of showers and thunderstorms as gusty winds and rough seas may be encountered north and south of the island.
The Meteorological Service will continue to monitor the situation.
LOL
Hi from trinidad,thats terrible,we could use some of that rain here.
Model Cycle: 2009052118
North America: Model Tracks for Mid-Latitude Cyclones
18Z GFS
18Z Multi-Model
Covering a large area about 700 miles from East to west in my estimation.
or west to east.
I do believe Shear is more than 20Kts......the tops are being blowed off anything trying to gather..
Now look right where the big glob is that you're all talking about. I want you to see how to the left of the blob the wind barbs are aiming towards the NE. Now look to the right of the blob. The wind barbs point towards the east or ESE.
So what's happening is the upper-level air-flow is splitting in that area due to the ULL in the gulf of Mexico, causing two separate air streams to separate and pull away from each other. This is called diffluence. So think about it, air is getting transported away from that area, so new air needs to replace it. The only place that that air can come from is below (remember this is taking place in the upper atmosphere). This causes a bunch of air to rise from the surface, and we all know that when air rises it condensates, forms clouds, and when strong enough, thunderstorms. That is all that this is, it is baroclinic process not tropical process. There is no threat of development from this area of thunderstorms.
LMAO
LOL
NEXRAD Radar
New Orleans, Composite Reflectivity Range 124 NMI
NEXRAD Radar
New Orleans, Storm Relative Mean Radial Velocity 0.50 Degree Elevation Range 124 NMI
Coastal Flood Warning
Statement as of 3:59 PM CDT on May 21, 2009
... Coastal Flood Warning in effect until 7 PM CDT Saturday...
The National Weather Service in New Orleans has issued a coastal
Flood Warning... which is in effect until 7 PM CDT Saturday. The
coastal Flood Watch is no longer in effect.
An area of low pressure will result in moderate to strong
northeast and easterly winds through Friday. These winds will pile
water along east facing shores from near Bay St. Louis to Port
Fourchon and increase tides further above normal over the next
couple days.
Tide levels were already running one to one and one half feet
above normal near Waveland Mississippi and Lake Borgne around the
time of high tide late this morning. The onshore winds will
continue to cause water levels to rise to 2 to 2.5 feet above
normal around the time of high tide Friday. Tides may reach one to
one and one half feet above normal farther west from Southwest
Pass of the Mississippi River to Port Fourchon.
Minor flooding of low lying roadways may occur in Hancock County
Mississippi... and minor flooding of low lying areas may occur
outside of hurricane protection levees from near Lake Catherine
and Lake Borgne... to Grand Isle and Port Fourchon.
Precautionary/preparedness actions...
A coastal Flood Warning means that flooding is occurring or
imminent. Coastal residents in the warned area should be alert
for rising water... and take appropriate action to protect life
and property.
What is a Rex Block?
NexSat GOM
METEOROLOGIST JEFF HABY
The Rex Block is a blocking pattern that in relation to the United States occurs most often in the spring and most often occurs along or near the West Coast. A Rex Block has two adjacent highs and lows. The most impressive Rex Blocks will have a strong low pressure next to a strong high pressure. The high pressure will be located in a generally north direction from the low pressure. The low associated with the Rex Block is not completely cut-off from the upper level flow, but does have little east-west movement. Strong ridging north of the low causes the airflow to move from high latitudes to low latitudes with little comparable west-east movement of the air. The airflow pattern follows a backward "S" trajectory. In the example image, air flowing into the West Coast of Canada then flows south into the Pacific off the Mexican West Coast
Popcorn thunderstorms still fizzling as soon as they form due to westerly shear from the ULL. You can see their cirrus debris being carried ESE over the center. The ULL is still displaced to the north of the surface low, and as a result the westerly winds on the southern side of the ULL are shearing the thunderstorms trying to form near the surface center. If this low can't get vertically stacked it will tear itself apart. Divided we fall....
Levi,
Thanks for the "Baro" clinic, from here in the Turks and Caicos, (under the split between the two separate air streams) We don't need more rain.
CRS
[edit] ...I guess I could say that this evening I am "under the diffluence" ...NOT under the Influence.
You just seem to be able to do it so fast.
Lol very funny CRS. I am sorry about the rain. Hopefully it will move on soon.
Not that Im aware of.
Having multiple Tabs Opens allows me ez access to a Lot of er,stuff I have stashed.
Showers/t-storms affecting the Dominican Republic and Puerto Rico as well.
yeah, the roads in St. Thomas are impassable hope you get the rain that you need. :)
Great explanation!
Anyone willing to go out on a limb and say no kidding, it will turn into invest 91L?
I hesitate to use the term "will" because the NHC has an extremely inconsistent track record on what they do name and what they don't. Even what they label an invest is inconsistent. IMHO I think it should be labeled an invest, but I have no clue how the NHC will treat this system.
If you look closely you can see the ULL directly NNE of the surface center. The trick is to look at the cirrus and not the low-level clouds. The cirrus appear more milky and transparent. Then it becomes quite obvious how tilted this system is and how it is shearing itself to pieces.
Viewing: 501 - 551
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