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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Quoting atmoaggie:

No, you've got it right. Instability over the low-latitude, northern hemisphere ocean peaks at sunrise, minimum at sunset in the summer. Not really settled reasons for it, but my favorite is:
Dynamic radiation-convection (DRC) interaction: "Daytime [convection] suppression [and hence nocturnal dominance] results from clear regions experiencing less subsidence warming in response to ongoing radiative cooling because of enhanced daytime radiative heating due to water vapor insolation absorption, thus reducing convergence into the convection zone and inhibiting daytime convective growth." Note that this theory "is only applicable to extended organized convection ... where background subsidence can be altered at regional scales."

From this neat analysis and write up: http://horizon.ucsd.edu/maltmn/Mike/mikepritchard.org/bib/YanSmi08/index.html


ok awesome, thanks!
so why does Erika flare up in the evening then?
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Quoting IKE:


You forgot one...or is it two?

El Nino.

Just to show how bright I am...I washed my car this morning after driving over soggy dirt roads yesterday afternoon in my job. Within an hour after washing it, it rained.

That always happens. Waste of water.
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Just checking in and Erika is looking bad i aint surprised that the NHC is calling for possible death of this system...shear looks to be quite harsh over the coming days
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I know the models do not have a good handle on Erika now, but I was looking at this and it takes quite a shift to the west at the end.
Link
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Quoting rwdobson:


Considering how insightful and accurate your forecasts were for Bill, we should all pay close attention to you! You were dead on with your predictions of a disastrous late evacuation on the east coast.


I think he said something about " millions will die "
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Floodman - You missed WeatherStudent earlier, he was on the blog then... So no one collected.

I thought you might like the little jab I gave you earlier...
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Quoting tornadodude:


i thought D-max was in the morning and D-min at night?
im probably wrong

No, you've got it right. Instability over the low-latitude, northern hemisphere ocean peaks at sunrise, minimum at sunset in the summer. Not really settled reasons for it, but my favorite is:
Dynamic radiation-convection (DRC) interaction: "Daytime [convection] suppression [and hence nocturnal dominance] results from clear regions experiencing less subsidence warming in response to ongoing radiative cooling because of enhanced daytime radiative heating due to water vapor insolation absorption, thus reducing convergence into the convection zone and inhibiting daytime convective growth." Note that this theory "is only applicable to extended organized convection ... where background subsidence can be altered at regional scales."

From this neat analysis and write up: http://horizon.ucsd.edu/maltmn/Mike/mikepritchard.org/bib/YanSmi08/index.html
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Quoting keys33070:
I know their outlook is bunk, but the Weather hannel just said Erika will either be a fish, or a rain event for the islands ---- thoughts?


They follow the NHC call pretty much...in looking at the averages, it's the safe bet.
Member Since: August 2, 2006 Posts: 10 Comments: 9922
Quoting TriniGirl26:
thank you btwntx08 and tornadodude :)


youre welcome!
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Anyone with credentials to do so mind explaining how the upper Saharan Air Layer that Masters is mentioning can possibly dump downwards into such a 'vertically challenged' system?
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Interesting are the opinions of Erika's current. Had she been no more than a wave 12 hours ago many would be saying she looks pretty good at the moment. Since she was a 60 mph storm 12 hours ago many say she looks horrible at the moment. Don't be too quick to pass judgement on her just yet...
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The problem with Puerto Rico is that there are 4 million people on that island. That compares to a city like Miami having only 500,000 or so folks. San Juan is a large metropolis surrounded by extensive suburban concentrations of vast numbers. These 4 million people await Erika.
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Looks like the year of shear in the Atlantic, Erika will die the same death as Anna..
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thank you btwntx08 and tornadodude :)
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Quoting Floodman:


He hasn't been around for a while...you don;t suppose someone collected, huh?

He has been in here this morning. Darnit.
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D-max in Puerto Rico
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191. IKE
Quoting Patrap:


3 Words,..Ike

Shear,Diffuse,De-coupled.



You forgot one...or is it two?

El Nino.

Just to show how bright I am...I washed my car this morning after driving over soggy dirt roads yesterday afternoon in my job. Within an hour after washing it, it rained.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting stormno:
ericka is biting i to some big time shear and its only going to get worse guys i cant see how you didnt see this yesterday...you guys really just wishcast ..you need to start looking at reality ERICKA WILL BE SUCKED UP LIKE A VACCUUM..LONG LIVE ERICKA..I THINK THAT MAKES ME 5 FOR 5 THIS YEARS GUYS..Stormno

You said Erika wouldn't make TS status, 4 for 5. And If i remember right you said Claudette wouldn't wouldn't get TS status either, 3 for 5 now. If you stopped blowing your own horn people might start to like you. Btw, don't bother replying to me. Your back on my ignore list now, and you will stay there permanently.

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Quoting Floodman:


He hasn't been around for a while...you don;t suppose someone collected, huh?


He was here earlier..
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Erika is not going north the next couple of days.The only thing that we will see going north is a pinguin.
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Quoting divdog:
stormno

coming from a guy who said it would never become a TS. Credibility is at an all time low.

Thats not saying much.
Member Since: August 3, 2008 Posts: 16 Comments: 5882
I know their outlook is bunk, but the Weather hannel just said Erika will either be a fish, or a rain event for the islands ---- thoughts?
185. Relix
Hmm it's looking like Erika will die before even getting close to PR.

*puts crow back in the fridge just incase
Member Since: August 3, 2006 Posts: 0 Comments: 2723
Quoting IKE:


Actually the GOM may have something by the Labor Day. Keep an eye out on it. Even the NO mets talk about a low in the GOM early next week and it's not Eri-ka.


Kinda Like Cracker-Jack Candy,..we may get a Surprise inside.
Member Since: July 3, 2005 Posts: 424 Comments: 128316
Quoting TriniGirl26:


HA HA, seriously...ur a met student...whats D Max?

haha yeah,just playing around,
D-min occurs at night right before sunset and D-max occurs in the morning right before sunrise, i think
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Quoting Floodman:


He hasn't been around for a while...you don;t suppose someone collected, huh?

I think he bet his life again recently that Erika would hit SFL he's running out of lives!
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Sounding from 8AM EDT from Saint Marten.

Note how the temperature and dewpoint (two black lines) diverge above 750mb or so...

This is DRY DRY DRY air. Also, you can see the 20-25 knot WSW or SW wind shear between 300 and 200 mb.


Saint Marten Sounding
Quoting FLdewey:
Hey lighten up, we all have our bad forecasts... Heck Weatherstudent bet his life on Danny impacting the CONUS. That went well. ;-)
please don't reference that person
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177. IKE
Quoting NRAamy:
It doesn't have to be catastrophic to be of interest does it?

it does to the kiddies...but they're still in school, so we're ok for awhile...


Exactly. Advance forward about 4 hours.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting SQUAWK:
Doah!! Ike is gonna look like a genius again!!

"MOST OF THE GLOBAL MODELS DO
NOT SHOW MUCH RELAXATION OF THIS SHEAR...AND ACTUALLY SHOW IT
INCREASING SIGNIFICANTLY IN A COUPLE OF DAYS. DESPITE ALL THIS
SHEAR...ALL RELIABLE GUIDANCE RESTRENGTHENS THIS SYSTEM TO NEAR
HURRICANE STRENGTH IN A FEW DAYS. THIS REINTENSIFICATION
DOES NOT SEEM VERY LIKELY AND THE NHC FORECAST IS MUCH LOWER THAN
THE GUIDANCE. GIVEN THE POSSIBLE SHEAR DURING THE FORECAST
PERIOD...IT WOULD NOT BE SURPRISING IF ERIKA DISSIPATED."


Dunno about that - all that graf says is that the future is uncertain.

But I love it when Franklin gets all hot and bothered about the models like that.
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Quoting TriniGirl26:
stupid question: What is D Max?

Strongest batteries that Duracell makes..JOKE! :)
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Quoting tornadodude:

Internet in Puerto Rico, jkjk


HA HA, seriously...ur a met student...whats D Max?
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Quoting FLdewey:
Hey lighten up, we all have our bad forecasts... Heck Weatherstudent bet his life on Danny impacting the CONUS. That went well. ;-)


He hasn't been around for a while...you don;t suppose someone collected, huh?
Member Since: August 2, 2006 Posts: 10 Comments: 9922
171. IKE
Quoting Seflhurricane:

go watch the gulf for us !


Actually the GOM may have something by the Labor Day. Keep an eye out on it. Even the NO mets talk about a low in the GOM early next week and it's not Eri-ka.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting IKE:
Can anyone really blame the NHC for their outlook?



3 Words,..Ike

Shear,Diffuse,De-coupled.

Member Since: July 3, 2005 Posts: 424 Comments: 128316
It doesn't have to be catastrophic to be of interest does it?

it does to the kiddies...but they're still in school, so we're ok for awhile...
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Quoting Dakster:


LOL.... At leasr you spelled HEBERT correct. Although I disagree that is voodoo... It seems to be backed up by some pretty decent historical fact. (Not that 150 years of data is really historical for the EARTH).

Although, Floodman can probably fill in the missing several thousand years - since he said he remembers when dirt was new and dinos roamed the Earth...


Smarta$$! It's like being in the blog with my kids, LOL!
Member Since: August 2, 2006 Posts: 10 Comments: 9922
165. IKE
Can anyone really blame the NHC for their outlook?

Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting TriniGirl26:
stupid question: What is D Max?

Internet in Puerto Rico, jkjk
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I wish people wouldn't say "next" when a system that's been unpredictable thus far is about to impact land. It doesn't have to be catastrophic to be of interest does it?
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stormno

coming from a guy who said it would never become a TS. Credibility is at an all time low.
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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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