Erika steadily weakening

By: Dr. Jeff Masters , 7:43 PM GMT on September 03, 2009

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Tropical Storm Erika has weakened steadily this afternoon, and has not generated any sustained winds of tropical storm force (39 mph) at any weather stations in the Lesser Antilles Islands today, according to our wundermap for the region. Erika has dumped some heavy rain on the islands, with 8.03" of rain measured on Dominica over the past two days. The Hurricane Hunters are in the storm now, and have thus far found top winds of 36 mph at the surface and at their flight level of 1000 feet. Radar animations out of Martinique show that the areal coverage and intensity of rain echoes has diminished greatly since this morning, and IR satellite loops also show a major decrease in heavy thunderstorm activity. Visible satellite images (Figure 1) show that the low-level center has become exposed to view, and there is very little heavy thunderstorm activity near Erika's center. Erika is probably just a tropical depression now.


Figure 1. Visible satellite image of Erika showing the exposed swirl of its low-level center southeast of Puerto Rico.

The forecast for Erika
Erika is headed west, in defiance of most of the computer models that predicted a northwest or west-northwest track. Regardless, Erika's track will take the storm into a band of significantly higher wind shear of 25 - 35 knots, Friday through Saturday. Considering that Erika is steadily weakening and is barely alive now, the storm should dissipate by Saturday, and perhaps much sooner. Erika's remains will still be capable of dumping very heavy rains of 3 - 5 inches over the Dominican Republic, Puerto Rico, and the northern Lesser Antilles Islands, and 1 - 3 inches over Haiti and the Southeast Bahamas over the next few days. However, the recent decrease of Erika's heavy thunderstorms makes lower rainfall totals more probable. By Monday, when the remains of Erika should have penetrated through the band of high wind shear over the Greater Antilles, shear may fall low enough to allow redevelopment. This is a scenario offered by the NOGAPS and GFS models. The other models predict quite a bit more shear in the region, and I believe any redevelopment of Erika early next week is unlikely. The GFDL and HWRF models continue to insist that Erika will head northwest, brush off the high shear, and intensify into a Category 2 hurricane five days from now.

McAfee virus alert messages
A number of wunderground users with the McAfee virus protection software installed were alerted yesterday that a possible Trojan virus existed on our web pages. After an investigation of the issue, we have determined that this is a false alarm. It appears McAfee updated their virus files yesterday, and included in their list of suspected viruses JavaScript web pages that compressed using the packer compression system used by wunderground. We've changed the compression technique used on our web pages, and hopefully this will eliminate the bogus McAfee alert messages.

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 continues to predict development of this wave into a tropical depression early next week.

I'll have an update Friday.

Jeff Masters

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1696. canehater1
3:10 PM GMT on September 04, 2009
Isn't it possible that Erika's remnants could
drift Westward as far as Yucatan Channel before
she is picked up by the trough? Looking at the
surface map, the trough has weakened over the
south gulf and the front has basically washed out.
Member Since: September 8, 2008 Posts: 1 Comments: 1010
1695. TropicalGenesis
2:50 PM GMT on September 04, 2009
Maybe Erika will begin a loop today - south -then East - North and return West. Heck, that is about all we need in PR. A storm that just won't go away.

Member Since: August 16, 2008 Posts: 0 Comments: 103
1693. mikatnight
2:42 PM GMT on September 04, 2009
Quoting StormW:


What they have stated is apparently true.

What I was trying to point out, is the mechanics of it.


Thanks Storm,

Appreciate the input. Lived in SE Fla my whole life and have always been told greatest chance for a tornado was after the main body of the storm passes (be damned if I can find any quotes to back me up though). I was thinking that vortices within the eyewall (miniwhirls, as Tetsuya Fugita described them in Hurricane Andrew) were being confused with the term “tornado” – a distinction I admittedly have a hard time understanding.
Member Since: October 18, 2005 Posts: 4 Comments: 3052
1691. apocalyps
2:39 PM GMT on September 04, 2009
Quoting KEEPEROFTHEGATE:
apocalyps erika is blowing you right into empty space


To funny,i already live overthere.
Member Since: May 10, 2007 Posts: 0 Comments: 960
1690. CaicosRetiredSailor
2:38 PM GMT on September 04, 2009
Quoting NOLAGuy:
Sounds like most say it is right front quadrant would be the most accurate way to describe the most dangerous sector ...



http://hurricanes.noaa.gov/pdf/hurricanebook.pdf

Hurricane
Basics



The Right Side of the Storm
As a general rule of thumb, the hurricane's right
side (relative to the direction it is travelling) is
the most dangerous part of the storm
because of
the additive effect of the hurricane wind speed and
speed of the larger atmospheric flow (the steering
winds). The increased winds on the right side
increase the storm surge. Tornadoes are also more
common here.

Looking at the figure above, pretend you are
standing behind the hurricane with your back to the
steering flow. In this case, the right side is the
eastern section of the hurricane. (If it were travelling
east to west, the right side would be the north
section.) The winds around the hurricane's eye are
moving in a counterclockwise fashion. At Point A,
the hurricane winds are nearly in line with the
steering wind, adding to the strength of the winds. For example, if the steering currents are 30 mph and the average
hurricane winds are 100 mph, the wind speed would be 130 mph at Point A. On the other hand, the winds at Point B
are moving opposite those of the steering wind and therefore slow to 70 mph (100 - 30 mph). Incidentally, National
Huricane Center forecasts take this effect into account in their official wind estimates.



[edit] since this is a .pdf, I was unable to link the illustration.
Member Since: July 12, 2007 Posts: 0 Comments: 5996
1687. KEEPEROFTHEGATE (Mod)
2:37 PM GMT on September 04, 2009
apocalyps erika is blowing you right into empty space
Member Since: July 15, 2006 Posts: 169 Comments: 53296
1686. TriniGirl26
2:36 PM GMT on September 04, 2009
Quoting Relix:
I am not kidding you when I tell you this has been one of the most beautiful days ever here here I live. Crystal clear blue sky! =O



Do you see a beach anywhere close by?
Member Since: August 18, 2009 Posts: 0 Comments: 201
1684. justalurker
2:36 PM GMT on September 04, 2009
back again,

went back read all the posts since this morning, you know what, 1 hour of reading, of (except few posts)..*i think* *i saw* *i see* *i predict* * i know * *now dead* *erka2* *convetion* *reborn*..hahaha

i knew we couldnt keep from bashing each other..
Member Since: August 18, 2009 Posts: 0 Comments: 157
1683. Relix
2:35 PM GMT on September 04, 2009
I am not kidding you when I tell you this has been one of the most beautiful days ever here here I live. Crystal clear blue sky! =O
Member Since: August 3, 2006 Posts: 0 Comments: 2645
1680. scottsvb
2:33 PM GMT on September 04, 2009
Quoting Relix:
I think Erika is about to breathe her last.



she did that and went to eternal sleep late last night... Erika is no more...no west winds and barely any south winds....just typical east to northeast winds as a wave-trough.
Member Since: January 22, 2006 Posts: 0 Comments: 1600
1679. DocBen
2:33 PM GMT on September 04, 2009
Erika - it takes a licking but keeps on ticking ...
Member Since: May 16, 2006 Posts: 0 Comments: 98
1678. gordydunnot
2:32 PM GMT on September 04, 2009
Yikes
Member Since: August 18, 2008 Posts: 0 Comments: 3112
1675. mikatnight
2:30 PM GMT on September 04, 2009
From the NHC (doesn't seem to prove either point):

Tornado Facts

When associated with hurricanes, tornadoes are not usually accompanied by hail or a lot of lightning, clues that citizens in other parts of the country watch for.

Tornado production can occur for days after landfall when the tropical cyclone remnants maintain an identifiable low pressure circulation.

They can also develop at any time of the day or night during landfall. However, by 12 hours after landfall, tornadoes tend to occur mainly during daytime hours.

Member Since: October 18, 2005 Posts: 4 Comments: 3052
1674. lurkn4yrs
2:28 PM GMT on September 04, 2009
Apocalyps:

My email probably has not reached you because i did not send you one.
You should thank me for that.




Oh man! I'm so sad now.. Who else is gonna make my day so special..
Member Since: August 15, 2009 Posts: 0 Comments: 90
1673. gordydunnot
2:27 PM GMT on September 04, 2009
Check your radar.
Member Since: August 18, 2008 Posts: 0 Comments: 3112
1671. canehater1
2:26 PM GMT on September 04, 2009
Quoting sarahjola:
we just got a special marine warning in Louisiana for gom. it said from pascagoula ms. southwest. don't see anything too dangerous in that area. does anyone else see anything?


That is a special marine warning for tstms in offshore waters between pascagoula and sw pass , mississippi river....
Member Since: September 8, 2008 Posts: 1 Comments: 1010
1670. apocalyps
2:26 PM GMT on September 04, 2009
Quoting lurkn4yrs:




It sure did!


My email probably has not reached you because i did not send you one.
You should thank me for that.
Member Since: May 10, 2007 Posts: 0 Comments: 960
1669. Cotillion
2:25 PM GMT on September 04, 2009
Is there a theoretical maximum for sustained winds?

I'm talking more hurricanes than tornadoes, of course.

(I say sustained, I'm sure gusts would be a lot harder to pin down.)
Member Since: August 23, 2008 Posts: 7 Comments: 5300
1668. viequessun
2:25 PM GMT on September 04, 2009
Quoting StormW:


LOL!
Good morning to you too!

Did my email come through?
Mr Storm W when you do you think we will begin feeling the Rain from Erika here in Puerto Rico
Thanks in advance seems to me you know whats going on with Erika!
1667. Orcasystems
2:25 PM GMT on September 04, 2009
Off to the tropical rainforest.. then work.


AOI

AOI

AOI

AOI

Member Since: October 1, 2007 Posts: 81 Comments: 26511
1666. 954FtLCane
2:24 PM GMT on September 04, 2009
Quoting stormsurge39:
The so called death of Erika is way overated!


aren't you a troll?... hmmmmmm
Member Since: September 30, 2008 Posts: 0 Comments: 108
1665. KS4EC
2:24 PM GMT on September 04, 2009
Quoting gordydunnot:
That sounds like one for Storm W, but I imagine that it boils down to most storms travel west or north or some combination of those two directions, so if a storm is moving in this direction at say 15 mph, you have to subtract 15 on one side and add 15 on the other . There are probably other forces involved but that's all I can add.


Max winds take into account for motion so if a 100mph storm is moving 15mph to the N then winds on the East would be 100, winds on the north would be ~85 out of the east and winds on the West would be ~70 out of the North, all things being equal and speeds are windspeed over the ground.

Did I get that right Storm?
1664. lurkn4yrs
2:23 PM GMT on September 04, 2009
Quoting StormW:


LOL!
Good morning to you too!

Did my email come through?




It sure did!
Member Since: August 15, 2009 Posts: 0 Comments: 90
1663. gordydunnot
2:22 PM GMT on September 04, 2009
How is the bp doing se of New Orleans. Pat's favorite met., predicted something in the gulf were is kerry and stormno, no need to panic if they aren't on it.
Member Since: August 18, 2008 Posts: 0 Comments: 3112
1662. rwdobson
2:22 PM GMT on September 04, 2009
Quoting mikatnight:


Hi Storm. Tornadoes...in the RF quadrant? Votecies (miniwhirls according to Fugita), but I thought tornadoes usually came with the passing of a hurricane?


The tornadoes from a landfalling hurricane are caused by the friction of high winds interacting with land. Since the highest winds are in the RF, the greatest chance of tornadoes is there too.
Member Since: June 12, 2002 Posts: 0 Comments: 1588
1660. sarahjola
2:22 PM GMT on September 04, 2009
we just got a special marine warning in Louisiana for gom. it said from pascagoula ms. southwest. don't see anything too dangerous in that area. does anyone else see anything?
Member Since: September 10, 2008 Posts: 0 Comments: 1291
1659. Magicchaos
2:22 PM GMT on September 04, 2009
My 11AM public advisory for Tropical Storm Dujuan
Member Since: April 3, 2009 Posts: 107 Comments: 382
1657. Elena85Vet
2:21 PM GMT on September 04, 2009
Quoting P451:




A couple of rapid scan loops (each frame = 7 minutes)







Thanks P451
Member Since: August 18, 2008 Posts: 0 Comments: 628
1656. iluvjess
2:23 PM GMT on September 04, 2009
Storm may correct me here but from my observations the swirl in the Gomex south of AL/MS is in the upper levels and has little to no chance of reaching the surface. The Gomex prospect will be the splitting of the trough this weekend... Storm???
1655. lurkn4yrs
2:21 PM GMT on September 04, 2009
Quoting StormW:


Yep!




Good morning Mr. StormW aka weather god.. LOL
Member Since: August 15, 2009 Posts: 0 Comments: 90
1654. canehater1
2:20 PM GMT on September 04, 2009
Quoting P451:




A couple of rapid scan loops (each frame = 7 minutes)





Dont let Stormno see that ..we'll
never hear the end of it!
Member Since: September 8, 2008 Posts: 1 Comments: 1010
1653. stormsurge39
2:20 PM GMT on September 04, 2009
Quoting P451:




A couple of rapid scan loops (each frame = 7 minutes)





That doesnt look good
1652. mikatnight
2:20 PM GMT on September 04, 2009
Quoting StormW:


Yep!


Hi Storm. Tornadoes...in the RF quadrant? Vortices (miniwhirls according to Fugita), but I thought tornadoes usually came with the passing of a hurricane?
Member Since: October 18, 2005 Posts: 4 Comments: 3052
1651. stormsurge39
2:19 PM GMT on September 04, 2009
Quoting Relix:
I think Erika is about to breathe her last.
The so called death of Erika is way overated!
1650. gordydunnot
2:18 PM GMT on September 04, 2009
Oh My God I've got a million Mad Dog quotes but I cannot risk getting a permanent ban.
Member Since: August 18, 2008 Posts: 0 Comments: 3112
1649. Elena85Vet
2:18 PM GMT on September 04, 2009
Quoting NOLAGuy:
Sounds like most say it is right front quadrant would be the most accurate way to describe the most dangerous sector and that generally is NE quadrant for the US mainland and Carribean. Thanks for the responses.


That sums it up.
Member Since: August 18, 2008 Posts: 0 Comments: 628

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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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