Erika dumping heavy rain on the Lesser Antilles

By: Dr. Jeff Masters , 2:12 PM GMT on September 03, 2009

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Tropical Storm Erika is hanging together despite strong wind shear, and is bringing high winds and much-needed heavy rain to the Lesser Antilles Islands. Winds on the south shore of Dominica Island were sustained at 37 mph this morning, and 8.03" of rain have been measured at the airport over the past two days. Winds and rain at nearby islands have been less, according to our wundermap for the region. The Hurricane Hunters are in the storm now, and have generally encountered top winds of 40 - 45 mph at the surface. They did find one spot of 50 - 65 mph winds, but that was likely due to outflow from a strong thunderstorm, and is not representative of Erika's wind field.


Figure 1. Radar image of Tropical Storm Erika at 9:15am EDT 9/3/09. Image credit: Meteo France.

Erika has improved in organization a bit since last night, but remains weak and disorganized, thanks to about 20 knots of shear at the 200 mb level, as seen on last night's Guadeloupe upper air sounding. Radar animations out of Martinique show plenty of heavy rain moving through the Lesser Antilles, but little organization of the echoes. Satellite imagery shows no low-level spiral bands and little upper-level outflow. Long range radar out of Puerto Rico is beginning to show rain echoes from Erika approaching the island.

The forecast for Erika
The computer models have come into better agreement about the track of Erika, taking the storm west-northwest over Puerto Rico and the Dominican Republic. This track will take Erika into a band of significantly higher wind shear of 25 - 35 knots, Friday through Saturday. Considering that Erika is barely maintaining itself as a tropical storm with 20 knots of shear, the combined effects of the higher shear and the encounter with the high mountains of Hispaniola and Puerto Rico should be enough to cause Erika to dissipate by Sunday. Erika's remains will still be capable of dumping very heavy rains of 3 - 5 inches over the Dominican Republic and 1 - 3 inches over Haiti and the Southeast Bahamas, due to the slow motion of the storm. By Monday, when the remains of Erika should be over the Bahamas, the storm will have penetrated through the band of high wind shear over the Greater Antilles, and shear may fall low enough for redevelopment of the storm. This is a scenario offered by the NOGAPS model, which then takes Erika northward towards North Carolina. The other models predict quite a bit more shear in the region than the NOGAPS, and any redevelopment of Erika early next week remains an iffy proposition. The GFDL and HWRF models continue to insist that Erika will brush off the high shear this weekend, avoid Hispaniola, and intensify into a Category 2 hurricane five days from now. These models have not been giving enough emphasis to how the current shear is affecting Erika, and are being discounted at this time.

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Elsewhere in the Atlantic
A large, strong tropical wave with plenty of spin emerged from the coast of Africa this morning. The wave is not yet generating much in the way of heavy thunderstorms, but has the potential to gradually develop into a tropical depression by early next week. NHC is giving this wave a low (less than 30% chance) of developing into a tropical depression by Saturday. The GFS model has been consistently developing this wave in its runs over the past few days.

I'll have an update this afternoon.

Jeff Masters

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Quoting watchingnva:
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still seeing this...but its my own opinion and based off of current observations only...she could be gone in 6 hours if she doesnt keep a moderate level of convection around the circulation...

who knows...she needs to make her mind up though...lol

The ADD TS Erika.

A COC here, a COC there, here a COC, there a COC, everywhere a COC.
e - i - e - i - o
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I keep on having this visualization with Erika... she is like a woman that can't decide on which shoes to wear for a night out. Each COC that Erika "spits out" is like a pair of shoes she decides not to wear.

I will leave it up to the rest of you to run with that one.
Member Since: August 3, 2008 Posts: 16 Comments: 5880
>much-needed heavy rain to the Lesser Antilles Islands.

This was a factor in the move toward the islands. Obviously, there were some low level conditions that were influencing the changes in upper level patterns that the models did not pick up. Previous rainfall is a weakness in the models.
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Adrian, there is definitely still a circulation.
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Quoting masonsnana:

Is there still a RECON out there??


Yes.
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Post 852 - similar to what I referred to last night. It was either Andrew or Katrina, don't remember which, that was described during the discussions as a "pulsating" storm, ie not continuous, but in spurts.

The point last night was that two very bad storms had the same type of characteristics, no vigourous low level circulation, elongated centers, and wind shear issues. The point being that even storms that go on to become the largest storms we've had have the same characteristics as Erika.

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still seeing this...but its my own opinion and based off of current observations only...she could be gone in 6 hours if she doesnt keep a moderate level of convection around the circulation...

who knows...she needs to make her mind up though...lol
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Quoting hurricane23:


855. hurricane23 3:14 PM EDT on September 03, 2009
18z models were initialized at 30kts so theres your'e TD at 5pm. SHIPS upper level wind forcast has been beyond horrific with this tc if i can call it that. Not much of a circulation i can find based on obs out there looks like an open wave to me.

adrian

Is there still a RECON out there??
Member Since: February 14, 2004 Posts: 2 Comments: 663
Quoting mrnicktou:
To put it the nice way. What in the world are these models smoking?

Well, the TCHP input data was garbled, so they got THC.
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869. WXHam
Quoting futuremet:


Some spin is quite evident on the Martinique radar


It's going to be interesting to see what the HHs find in Mission 5.
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Updated 1:56:29pm
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Quoting atmoaggie:

This just about wouldn't qualify as a closed circulation for a new system to get TD status.


855. hurricane23 3:14 PM EDT on September 03, 2009

18z models were initialized at 30kts so theres your'e TD at 5pm. SHIPS upper level wind forcast has been beyond horrific with this tc if i can call it that. Not much of a circulation i can find based on obs out there looks like an open wave to me.

adrian
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Quoting TheCaneWhisperer:

This just about wouldn't qualify as a closed circulation for a new system to get TD status.
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I cant figure out how to post a picture.. but I have to say Ive never seen a NHC forecast track like the one currently... It shows a forecasted NE track with a swing to the NW. (I know its just because of the coc changing before the next track update... kinda funny to see it though)
Member Since: June 24, 2006 Posts: 0 Comments: 484
Quoting Cotillion:
We need stakes and holy water.

This thing doesn't want to die until it's literally becoming dust..


Real estate and mountains will do the trick.
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Lets stop fussing over this... ERIKA = DEAD!!
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Quoting WXHam:



Seems the islands may be in for a second view of the COC.img src="Two or shifting COCs" alt="" />


Some spin is quite evident on the Martinique radar
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Quoting OSUWXGUY:


When the NHC and others to do a seasonal recap, I want to see the difference between a "normal" years tropical sounding and this years.
There has been SOOOO much dry air that has killed waves.

Not to mention the waves themselves have been pretty weak this year (with a few exceptions - Bill for instance)

Now that it's later in the season it's not even the dust anymore, just the dryness of the environment...

I wonder if there is some subsidence going on not being measured...not usual for the tropics.
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12 Z Statistical Models


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Quoting StormW:


Actually, all I can say right now is...this is one of the most tenacious systems I've seen having 2 strikes against it...shear and subsidence.

Try to have another update this eve after some model updates.


Come on StormW, why don't you just speculate like the rest of us? Isn't more fun. I am coming to hate all those little models. We had spaghetti last night, and I was sure I saw some sauce on the bottom of the plate that looked just like Erika. Seriously, we are looking forward to what you find.
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Quoting Cotillion:


I was going from when it was 1010mb, or so it was said.

I corrected remark #850 :)
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18z models were initialized at 30kts so theres your'e TD at 5pm. SHIPS upper level wind forcast has been beyond horrific with this tc if i can call it that. Not much of a circulation i can find based on obs out there looks like an open wave to me.

adrian
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Quoting Orcasystems:
1 actually, the old one was 1008


I was going from when it was 1010mb, or so it was said.
Member Since: August 23, 2008 Posts: 7 Comments: 5300
853. WXHam
Quoting futuremet:


The eastern COC will likely becoming become dominant, because it is under the convection. Sigh...this seems to be a repeat of yesterday. I'd be satisfy if Erika would die right now.



Seems the islands may be in for a second view of the COC.img src="Two or shifting COCs" alt="" />
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Quoting Grothar:
Ed Rappaport
National Hurricane Center
Updated 10 December 1993 Hurricane Andrew Photos
a. Synoptic History
Satellite pictures and upper-air data indicate that Hurricane Andrew formed from a tropical wave that crossed from the west coast of Africa to the tropical North Atlantic Ocean on 14 August 1992. The wave moved westward at about 20 kt, steered by a swift and deep easterly current on the south side of an area of high pressure. The wave passed to the south of the Cape Verde Islands on the following day. At that point, meteorologists at the National Hurricane Center (NHC) Tropical Satellite Analysis and Forecast (TSAF) unit and the Synoptic Analysis Branch (SAB) of the National Environmental Satellite Data and Information Service (NESDIS) found the wave sufficiently well-organized to begin classifying the intensity of the system using the Dvorak (1984) analysis technique.

Convection subsequently became more focused in a region of cyclonic cloud rotation. Narrow spiral-shaped bands of clouds developed around the center of rotation on 16 August. At 1800 UTC on the 16th (UTC precedes EDT by four hours), both the TSAF unit and SAB calculated a Dvorak T-number of 2.0 and the "best track" (Table 1 and Fig. 1 [85K GIF]) shows that the transition from tropical wave to tropical depression took place at that time.

The depression was initially embedded in an environment of easterly vertical wind shear. By midday on the 17th, however, the shear diminished. The depression grew stronger and, at 1200 UTC 17 August, it became Andrew, the first Atlantic tropical storm of the 1992 hurricane season. The tropical cyclone continued moving rapidly on a heading which turned from west to west-northwest. This course was in the general direction of the Lesser Antilles.

Between the 17th and 20th of August, the tropical storm passed south of the center of the high pressure area over the eastern Atlantic. Steering currents carried Andrew closer to a strong upper-level low pressure system centered about 500 n mi to the east-southeast of Bermuda and to a trough that extended southward from the low for a few hundred miles. These currents gradually changed and Andrew decelerated on a course which became northwesterly. This change in heading spared the Lesser Antilles from an encounter with Andrew. The change in track also brought the tropical storm into an environment of strong southwesterly vertical wind shear and quite high surface pressures to its north. Although the estimated maximum wind speed of Andrew varied little then, a rather remarkable evolution occurred.

Satellite images suggest that Andrew produced deep convection only sporadically for several days, mainly in several bursts of about 12 hours duration. Also, the deep convection did not persist. Instead, it was stripped away from the low-level circulation by the strong southwesterly flow at upper levels. Air Force Reserve unit reconnaissance aircraft investigated Andrew and, on the 20th, found that the cyclone had degenerated to the extent that only a diffuse low-level circulation center remained. Andrew's central pressure rose considerably (Fig. 2 [87K GIF]). Nevertheless, the flight-level data indicated that Andrew retained a vigorous circulation aloft. Wind speeds near 70 kt were measured at an altitude of 1500 ft near a convective band lying to the northeast of the low-level center. Hence, Andrew is estimated on 20 August to have been a tropical storm with 40 kt surface winds and an astonishingly high central pressure of 1015 mb (Figs. 2 and 3 [87K GIF]).

Significant changes in the large-scale environment near and downstream from Andrew began by 21 August. Satellite imagery in the water vapor channel indicated that the low aloft to the east-southeast of Bermuda weakened and split. The bulk of the low opened into a trough which retreated northward. That evolution decreased the vertical wind shear over Andrew. The remainder of the low dropped southward to a position just southwest of Andrew where its circulation enhanced the upper-level outflow over the tropical storm. At the same time, a strong and deep high pressure cell formed near the U.S. southeast coast. A ridge built eastward from the high into the southwestern Atlantic with its axis lying just north of Andrew. The associated steering flow over the tropical storm became easterly. Andrew turned

I never post anything this big. Just for information.


There are sure some similarities between Andrew and Erika.
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.
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Quoting Cotillion:


That's about 3mb in a few hours.

1 actually, the old one was 1008, which was down from 1010 from the previous flight
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To put it the nice way. What in the world are these models smoking?
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Quoting Orcasystems:
Time: 19:00:30Z
Coordinates: 16.65N 64.9667W
Acft. Static Air Press: 987.1 mb (~ 29.15 inHg)
Acft. Geopotential Hgt: 175 meters (~ 574 feet)
Extrap. Sfc. Press: 1007.1 mb (~ 29.74 inHg)
D-value: -


That's about 3mb in a few hours.

Member Since: August 23, 2008 Posts: 7 Comments: 5300
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Quoting atmoaggie:

I think the big differentiation between Erika and what we are used to seeing is that Erika didn't cross some threshold in development that limits that diurnal effect.


Well said. It's taking about the same time to dissipate during the day as it is to build up at night. No significant overall gain or loss hence the model disruptions.
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The twist(s) on the GOMEX are way up high. Nothing to worry about at the moment.
Last evening I posted the Below as I felt Erika had only 3 Choices..and to be sure,..Size Matters again..and not many ever touched that angle. It Matters Greatly..always.

What most are forgetting is that this is a LARGE Cv Circ that has always had Multiple CoC's within the Mean Overall Circ..thats whats been its problem from Genesis.
What its doing is the same as Last evening..One coc is trying to Dominate.

Until One does in the Center of the Overall Mean Circ..it will repeat the last 24,or spin Out,.or Consolidate a New central CoC in the end.

00 UTC Multiplatform Satellite Surface Wind Analysis


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StormW--

How long will it be before the TUTT moves out of the GOM? With the TUTT in place it would be hard to have a system or a system making it through it right?
Member Since: August 30, 2007 Posts: 0 Comments: 1837
Time: 19:00:30Z
Coordinates: 16.65N 64.9667W
Acft. Static Air Press: 987.1 mb (~ 29.15 inHg)
Acft. Geopotential Hgt: 175 meters (~ 574 feet)
Extrap. Sfc. Press: 1007.1 mb (~ 29.74 inHg)
D-value: -
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Quoting Keys99:
For your Viewing Pleasure

View Of weather from Web Cam St Croix Harbor



href="http://www.gotostcroix.com/live/harborcam.php.html"

great webcam- i need to find one for st. johns. I have friends vacationing there
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Quoting atmoaggie:

That's what GFS was showing us with the Theta-e about a week ago through yesterday. This is why GFS continued to dissipate Erika.


When the NHC and others to do a seasonal recap, I want to see the difference between a "normal" years tropical sounding and this years.
There has been SOOOO much dry air that has killed waves.

Not to mention the waves themselves have been pretty weak this year (with a few exceptions - Bill for instance)

Now that it's later in the season it's not even the dust anymore, just the dryness of the environment...
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836. Relix
Quoting StormW:


Actually, all I can say right now is...this is one of the most tenacious systems I've seen haveing 2 strikes against it...shear and subsidence.

Try to have another update this eve after some model updates.


Hahaha, thanks Storm, will wait forward to that =)
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Quoting iceman55:
Erika hate sunnight. sheee like night.

I think Erika hates water, land, day, night, air, dust, water vapor, salt, birds, and bloggers.
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I love the fact that I do not have internet at home anymore. I couldn't imagine tracking this all night. Clears the head, lol.
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832. Relix
Well that's that I am off. Won't be on for a while, maybe tomorrow. Erika seems to have finally died down and will probably not even bring many rains at all at PR. The government did cancel all activities tomorrow so I am free until next Tuesday from any work or college =P. Will just take some long vacations and just going out over the weekend. Should be a wet friday probably. Sayonara WU, see you soon again.. probably in about 8 hours me checking out what's happening =P
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Quoting Floodman:


No, there's a NW component to the movement at that point...but before you get your undies all bunched up, remember that these models are anywhere from 144 hrs to 168hrs out and the data in those images is old...the 18Z run may show dissipation



Thanks Flood No Bunching here I am way south of there.( not a Ga wish caster) Just in the picture posted could not tell the direction of movement. I am in the BAMS Camp as to her movement
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We need stakes and holy water.

This thing doesn't want to die until it's literally becoming dust..
Member Since: August 23, 2008 Posts: 7 Comments: 5300

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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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