Tropical Storm Erika's future highly uncertain

By: Dr. Jeff Masters , 2:21 PM GMT on September 02, 2009

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The tropical wave we were calling Invest 94 finally decided to stop dawdling and become Tropical Storm Erika yesterday. However, Erika seems intent upon keeping us guessing about its intentions, as the storm's future track and intensity remain highly uncertain. After a modest burst of intensification to a 60 mph tropical storm last night, Erika has become quite disorganized this morning. The Hurricane Hunters found multiple swirling centers inside Erika early this morning, and the main center took a jump to the southwest to relocate itself under a batch of intense thunderstorms. The exact location and path of Erika remain uncertain at this point, and it is possible the storm will have another center relocation later today. Wind shear analyses from the University of Wisconsin diagnose a moderate 10 - 15 knots of shear over Erika, a decrease from yesterday. SSTs are warm, 29°C. Why, then, is Erika so disorganized? The trouble with the various wind shear analyses we use is that they take a crude average of winds over a thick layer to arrive at an average shear, and this large-scale average shear does not capture thin layers of shear that can dramatically affect a tropical cyclone. Upper air data from Guadeloupe and Saint Martin from last night show a complicated shear pattern in Erika's region, with 30 knot winds out of the south to southwest at 200 mb height, nearly calm winds between 300 - 500 mb, and northeasterly winds of 10 - 20 knots from the surface to 500 mb. Some extremely dry air with humidities near 10% was present in a thin layer near 600 mb on the Guadeloupe sounding, so dry air from the Saharan Air Layer is probably being injected by a northeasterly jet of wind into the core of Erika. The shear of 30 knots at the top of the storm is ripping away the heat and moisture Erika's thunderstorms are lifting there, and the result of the shear and dry air is a very disorganized tropical storm.

Erika is embedded in a weak steering current pattern, and the future track of the storm will depend greatly upon how strong the storm gets over the next few days. A stronger Erika will extend higher into the atmosphere and be steered more to the northwest by upper-level winds. A weaker Erika will be steered more by the low-level winds, which will keep the storm on a more westerly track. Given the complicated nature of the wind shear pattern in the region, it is difficult to forecast how strong Erika will get. Virtually anything can happen over the next five days, from dissipation (as forecast by the ECMWF model) to intensification to a Category 3 hurricane (as forecast by the HWRF model). Large-scale wind shear is expected to increase to 20 - 25 knots between 3 - 4 days from now, so Erika will have to deal with an increasing amount of adversity. The storm is a long-term threat to the Bahamas and U.S. East Coast, particularly if the storm stays weak over the next three days. Potential landfall solutions from the models range from Florida on Tuesday (GFS model) to North Carolina on Wednesday (Canadian model).


Figure 1. Morning image of Tropical Storm Erika, showing a false center over Guadaloupe--one of several surface swirls the Hurricane Hunters found in the storm.

Elsewhere in the tropics
The tropical wave off the coast of Africa we were watching on NHC's Tropical Weather Outlook as having a low chance of developing into a tropical depression has been done in by the dry air of the Sahara, and is no longer a threat to develop. A large and well-organized tropical wave will emerge from the coast of Africa on Thursday, and several of the models develop this low into a tropical depression by early next week. The remains of an old cold front off the coast of North Carolina could serve as a breeding ground for some tropical development Friday or Saturday, but anything that forms in this region would get swept quickly northeastward into New England by Sunday without enough time to become a tropical depression.

Hurricane Jimena nears Baja
Hurricane Jimena has steadily weakened over the past day, and is now down to a Category 2 hurricane with 105 mph winds. The storm should continue to steadily weaken over the next 24 hours as the waters under the hurricane cool from 28°C to 27°C. Jimena is battering a relatively unpopulated stretch of coast, and largely spared the tourist mecca on the southern tip of Baja. It now appears unlikely that moisture from Jimena will reach the Southwestern U.S., and the hurricane appears poised to stall out over Baja and die five days from now.


Figure 2. Hurricane Jimena on Tuesday, Sep. 1, 2009, as seen by NASA's MODIS instrument. Image credit: NASA Earth Observatory.

Baja's hurricane history
The most powerful hurricane on record to hit the west coast of Baja occurred last year, when Hurricane Norbert made landfall on the central Baja coast with sustained winds of 105 mph (Category 2) . Norbert's central pressure of 956 mb at landfall made it the 3rd strongest hurricane to hit the Pacific coast of Mexico since record keeping began in 1949. Norbert killed eight, knocked out power to 20,000 homes, and damaged or destroyed 40% of the homes on the islands of Margarita and Magdalena. Norbert crossed the Baja Peninsula and made landfall on Mainland Mexico as a Category 1 hurricane with 85 mph winds.

Only two major hurricanes have made landfall on Baja since record keeping began in 1949. Both hurricanes hit the east (Gulf of California) side of Baja. The first was Hurricane Olivia of 1967. Olivia made landfall on October 13, 1967 as a Category 3 hurricane with 125 mph winds. Due to its small size and the unpopulated region of coast it hit, damage was minimal. The second major hurricane was Hurricane Kiko, which made landfall on August 27, 1989, as a Category 3 hurricane with winds of 115 mph (minimal Category 3). Kiko was a small hurricane and hit a relatively unpopulated area, resulting in no loss of life and only scattered reports of damage.


Figure 3. A plot of all the major hurricanes to pass within 200 miles of Mexico's Baja Peninsula since 1949. Image credit: NOAA Coastal Services Center.

California fire webcams
As I discussed in yesterday morning's post, you can use our wundermap for Los Angeles with the fire layer turned on to see where the fire and smoke are located, and track the temperatures and winds during today's air pollution event. We also have two webcams with views of the fire: Altadena and Tujunga.

I'll have an update by 4pm this afternoon, when the data from the next hurricane hunter flight into Erika will be available.

Jeff Masters

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Given how unpredictable Tropical Storm Erika has been thus far, how divergent the computer models have been, and how uncertain the National Hurricane Center remains, I don't think anyone can say where and with what intensity Erika will go, not even me. This has been one of the most confusing systems thus far in my young weather career, so much so that when asked where Erika will go, I have to respond "I don't know." Good luck to the pros at the National Hurricane Center with this one.
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Tricky tricky system so far.
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Quoting jeffs713:

I think he was speaking about the kids getting home from school and clogging the blog with junk.


right on!!
Member Since: August 18, 2009 Posts: 0 Comments: 157
607. jpsb
Quoting TreasureCoastFl:
I'm sorry. I pasted it from WU shear explanation page. I found it interesting.
I read it, thanks.

It's just easier to read something broken into smaller paragraphs. I like to read the topic sentence and then decide if I want to read the rest of the paragraph. Doing that allows me to read really fast. I get to skip the stuff I don't need to read and read the stuff I do need to read. But with great big pantographs I have to decide weather to read the whole darn thing or skip it.

I usually skip it, lol, but this one I read.
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Quoting JLPR:
Re-post
I cant believe this isnt a invest

huh?




From where did this come from? =P

I posted the same thing(quikscat) early this morning but got no reply,I guess the NHC doesn't think it will a mount to much.
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Quoting CloudGatherer:


TreasureCoast:

Thanks for that cogent and articulate elucidation of the mysteries of wind shear. I agree with every word of it.

But my point is simply that, as you write: "upper-air measurements are very sparse over the open ocean, [leading to] wind shear that is invisible on 200-850 mb wind shear analysis charts." All true. So how, in any given instance, do we know that what's affecting the cyclone is wind shear that we can't see?

It's circular logic. We generally can't see upper-level jets that may be intruding on the cyclone, so we're left to infer their presence from the appearance of the cyclone. If it deforms, and we lack any other explanation for the deformation, it's gotta be the shear. And in most instances, it probably is. But in any particular case, I don't see how we would know that.

I'm sorry for not prefacing all that with my source which is WU. They weren't my words but I hear what you are saying. I suppose it is only in hindsight that one can say with any certainty at all that it was shear but never know 100% even then which would make it never certain when speculating which may be the reason for the "low level of certainty" disclaimers in the forecast?
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Quoting PanhandleChuck:


Hey Ms Muffin... I grew up in the Y-town area, where are u from?


Warren. I trust you know where that is. Ironically, I just came back from Youngstown an hour ago...
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603. IKE
Quoting connie1976:


Ike,
How many times have the models changed in 24hrs? lol


Quite a bit. I wouldn't bet on the GFS but...you never know.
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Quoting JLPR:
you can see the three areas here



The one in the CATL
the African wave to the north of the Cape Verde islands
and the tropical wave about to exit Africa


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Erika now has two centers.
One in Texas and one in Florida.
What a splitt.
The pinguin still going north and away from Erika.
Next advisory when i see a cow in the air and have to evacuate.
Member Since: May 10, 2007 Posts: 0 Comments: 960
Quoting southfla:


A commercial company tried developing a low-cost semi-automated balloon launcher for ships -- but they ended up running out of R&D funding. Also, the NWS wouldn't pay us to launch from the commercial ship we used because a hand launch can not be done with the turbulent wash of a ship when apparent winds get above 30mph. On a large ship moving 20 knots into a 10 knot wind -- well it just doesn't work well. (The balloon tends to dive into the water before it lifts.) So since we couldn't guarantee 0Z and 12Z launches they thought it wasn't worth it. It is too bad the commercial prototype never got off the ground so to speak, because it did work and could have been used on just about any ship at fairly high wind speeds.

Here is an image of the weather balloon launcher at work



That's very cool! Thanks for the info. Maybe once NOAA realizes that their prized models that they spend millions on won't get any better until better data is ingested...they'll turn to something like the automated balloon releases...
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Quoting JLPR:
you can see the three areas here


I believe the CATL one was very impressive when it came off, then just went into hiding. Any ideas if the next one off will head North? The one near the CV islands came off at 10N but went North right after exiting.
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Quoting truecajun:


do you live in mexico?

I think he was speaking about the kids getting home from school and clogging the blog with junk.
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Quoting IKE:
12Z GFS puts Erika in the GOM in 180 hours...


Ike,
How many times have the models changed in 24hrs? lol
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Quoting keys33070:
Just for fun---- what is everyones thoughts on how the models will change at 2

A little more westerly than they are right now....

Taco :0)
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Quoting apocalyps:
My pinguin is swimming north and Erika is not following him.I repeat NOT following him.
Next advisory soon.


Could you have him stop off in the bahammas and get me one of those fruity drinks in a coconut with a little umbrella, and bring it to me?
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Quoting EarthMuffin:


Time will tell. The models constantly change. I have seen a couple Florida trajectories, the rest show a shift north. Not to mention the distinct possibility that Erika may not survive to make a *ANY* CONUS landfall. I have no bias toward one location or another, I live in Ohio. No "wishcasting" or "downcasting" here, just observations.


Hey Ms Muffin... I grew up in the Y-town area, where are u from?
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Quoting truecajun:


do you live in mexico?

??????
Member Since: August 18, 2009 Posts: 0 Comments: 157
Quoting JLPR:
you can see the three areas here



The one in the CATL
the African wave to the north of the Cape Verde islands
and the tropical wave about to exit Africa


JL, saw the convergence/divergence map yesterday and both had positive numbers on that area behind erika. it's right in the itcz i believe tho
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591. JLPR
Quoting keys33070:
JLPR Is that what is behind Erika?


I did notice the NHC mentions it as a wave
TROPICAL WAVE EXTENDS FROM 16N40W TO 8N37W MOVING W 10-15 KT.
THIS WAVE REMAINS ILL-DEFINED AS IT HAS DRY AIR INTRODUCED AS
INDICATED BY TOTAL PRECIPITABLE WATER IMAGERY. WAVE IS ALSO
EMBEDDED WITHIN SAHARAN DUST THUS LIMITING ANY SHOWERS OR
CONVECTION.


But the latest quickscat says it has a very nice, closed LLC
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590. IKE
12Z GFS puts Erika in the GOM in 180 hours...
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589. eddye
ann there a 60 to 40 chance this miss es the islands
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Quoting EarthMuffin:
Based on what I have seen from the models over the past 24 hours, I still believe that *IF* Erika survives, the most likely CONUS landfall would be in the Carolinas, otherwise, I see it going up the Eastern seaboard to Canada or out to sea...period. I understand Florida and the GoM have had a "boring" hurricane season thus far, but that is no reason to develop a bias toward Florida/GoM storms. THUS FAR, the models and this season's history dont support it.


Hmmmm? Well like I said everyone's got a right to state their opinion. I hope it does dissipate or go out to sea. But you don't know any more than anyone else....PERIOD. :)
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Quoting Patrap:

Do you remember the old game show, "To Tell the Truth"? It's an old game show I watched growing up in the 60's. There was Bull Cullen, the host and 3 celebrities on the panel. They brought in an unusual or famous celebrity of the time in, a total of 3 people were claiming to be the same person. The celebrities would try to guess the real person! SO, "Will the correct computer model please stand up"!!
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This will most likely be revised on their next run. Depending on the re-location of the center of Erika, if it can be determined. (Is re-location the correct word) I know there was a heated debate last night about the use of "curve", "recurve", "recurvature", "recurvaturization" Enjoy the graphic and please do not ask me to explain it. I just post pictures without comment!
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there isn't one
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Hi, has anyone seen Stormno ... i belive he's been busy with all the crows in the oven
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Quoting justalurker:
this blog will sing to a different tune at 2pm when the next advisory comes out, and the convection starts to build up again..just wait and see.


do you live in mexico?
Member Since: August 24, 2006 Posts: 0 Comments: 1867
582. JLPR
you can see the three areas here



The one in the CATL
the African wave to the north of the Cape Verde islands
and the tropical wave about to exit Africa
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Quoting eddye:
sorry earthmuffin your wrong im sorry the models hifted more west


Time will tell. The models constantly change. I have seen a couple Florida trajectories, the rest show a shift north. Not to mention the distinct possibility that Erika may not survive to make a *ANY* CONUS landfall. I have no bias toward one location or another, I live in Ohio. No "wishcasting" or "downcasting" here, just observations.
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Quoting truecajun:


the main center relocated itself under convection that was southwest of its original location


Thanks! That's why I love this blog! I don't have to watch the Weather Channel for answers(which most of the time I don't get from them anyway). Thanks again. :)
Member Since: September 2, 2008 Posts: 0 Comments: 105
ok. i can't find her center. can someone give coordinates or is it still a mystery? i'm looking at her on noaa and trying to see what dr. m pointed to, but i don't see it. i can never truly see the darn things.
Member Since: August 24, 2006 Posts: 0 Comments: 1867
My pinguin is swimming north and Erika is not following him.I repeat NOT following him.
Next advisory soon.
Member Since: May 10, 2007 Posts: 0 Comments: 960
West to the DR was one of the two possible solutions I outlined on the earlier blog this morning. That would be a disaster for Haiti and the DR.
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Quoting BayouBorn1965:


Wasn't it cool? I was at my mom's in Mississippi when I experienced a sonic boom from a space shuttle. I ran outside to see what the heck happened, and then saw on the news that the space shuttle just returned. It was soooo cool!
Well, it rattles the house and scared the heck out of me but other than that it was kinda cool in hindsight. Many people called 911.. lol
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Quoting OSUWXGUY:


Having ships release ballons during hurricane season might not be a bad thing either...


A commercial company tried developing a low-cost semi-automated balloon launcher for ships -- but they ended up running out of R&D funding. Also, the NWS wouldn't pay us to launch from the commercial ship we used because a hand launch can not be done with the turbulent wash of a ship when apparent winds get above 30mph. On a large ship moving 20 knots into a 10 knot wind -- well it just doesn't work well. (The balloon tends to dive into the water before it lifts.) So since we couldn't guarantee 0Z and 12Z launches they thought it wasn't worth it. It is too bad the commercial prototype never got off the ground so to speak, because it did work and could have been used on just about any ship at fairly high wind speeds.

Here is an image of the weather balloon launcher at work



Member Since: May 19, 2009 Posts: 0 Comments: 252
JLPR Is that what is behind Erika?
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572. eddye
maryann is wrong because i see the anticyclone following it
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Quoting atmoaggie:

Sorry, just wanted to know where it came from. I am curious like that.

No problem. guess I was a little defensive. Easy to get that way on this blog ;)
It was from this site. I looked it up because shear confuses me.
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Quoting EarthMuffin:
Based on what I have seen from the models over the past 24 hours, I still believe that *IF* Erika survives, the most likely CONUS landfall would be in the Carolinas, otherwise, I see it going up the Eastern seaboard to Canada or out to sea...period. I understand Florida and the GoM have had a "boring" hurricane season thus far, but that is no reason to develop a bias toward Florida/GoM storms. THUS FAR, the models and this season's history dont support it.


Not wanting it to head into the GOM, but latest models do show a Westward trend... Again, I don't think anyone will be able to say where it will go until Friday sometime.
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Quoting BrockBerlin:
Erika looks like a lemon jbbho


lemon what? lol..
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568. eddye
nope lariann wrong
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Quoting TreasureCoastFl:

Wind shear is often the most critical factor controlling hurricane formation and destruction. In general, wind shear refers to any change in wind speed or direction along a straight line. In the case of hurricanes, wind shear is important primarily in the vertical direction--from the surface to the top of the troposphere. The troposphere is the region of the atmosphere that our active weather is confined to, and extends up to about 40,000 feet altitude (a pressure of about 200 mb) in the tropics in summer. Hurricanes fill the entire vertical extent of the troposphere, and are steered by the average wind through this layer. When one hears the phrase, "wind shear is 20 knots over the hurricane", this typically refers to the difference in wind speed between 200 mb (the top of the troposphere, 40,000 feet altitude) and a layer where a pressure of 850 mb is found--about 5,000 feet above the surface. This wind shear is computed over a large area--a circle of 700 miles in diameter centered on the hurricane is one technique used. This 200-850 mb wind shear is a crude measure of the actual wind shear a storm experiences, since only changes in wind speed--not wind direction--are considered. Furthermore, the computed shear does not consider any smaller scale changes that may occur within this large volume of the atmosphere. For example, it is common to find a strong jet of wind at about 600 mb blowing along the edge of the Saharan Air Layer (SAL)--that area of dry, dusty air that frequently lies to the north of developing tropical cyclones in the mid-Atlantic. This jet will create significant wind shear that will not show up on the standard 200-850 mb wind shear plots. Since upper-air measurements are very sparse over the open ocean, wind shear that is invisible on 200-850 mb wind shear analysis charts will often unexpectedly kill or weaken a developing tropical cyclone.


TreasureCoast:

Thanks for that cogent and articulate elucidation of the mysteries of wind shear. I agree with every word of it.

But my point is simply that, as you write: "upper-air measurements are very sparse over the open ocean, [leading to] wind shear that is invisible on 200-850 mb wind shear analysis charts." All true. So how, in any given instance, do we know that what's affecting the cyclone is wind shear that we can't see?

It's circular logic. We generally can't see upper-level jets that may be intruding on the cyclone, so we're left to infer their presence from the appearance of the cyclone. If it deforms, and we lack any other explanation for the deformation, it's gotta be the shear. And in most instances, it probably is. But in any particular case, I don't see how we would know that.
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Just for fun---- what is everyones thoughts on how the models will change at 2
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Quoting Prgal:

Yeah, what he said was uncalled for.


I will never know if he responds to it :)
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not gonna happen
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563. JLPR
Re-post
I cant believe this isnt a invest

huh?




From where did this come from? =P
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Seems to me that, after studying the floater #2 visible and infrared imagery, that the low, which is the essence of Erika, is moving west, out from under the anticyclone, leaving the convection area behind as well. If so, and it it continues, Erika will then be prancing west, totally naked. Does it look that way to anyone else?
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Don't be alarmed. The knots are not surface winds. This is for information only on the latest HWRF model forecast.
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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.