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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correct
Member Since: December 9, 2008 Posts: 0 Comments: 2498
Quoting Dakster:


Wrong. Miami-Dade has about 2.3 Million. If you include Broward and West Palm Beach you will get 5.5 Million...


my campus has 40,000
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Quoting rwdobson:


Miami, like San Juan, and pretty much all cities, is also surrounded by extensive suburbs. The population of the metro Miami area is about 5.5 million. It's always a mistake to look at the size of the main city and assume that it is the whole metro population.


Wrong. Miami-Dade has about 2.3 Million. If you include Broward and West Palm Beach you will get 5.5 Million...
Member Since: Posts: Comments:
There is an area of ?thunderstorms? over the south end of the bahamas right now. I am assuming is it nothing more than that. But could it have any impact on Erika in the days to come? It doesn't really seem to be moving much, just spreading...
don't agree
Member Since: December 9, 2008 Posts: 0 Comments: 2498
Quoting saltywaves:
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?

Post 15 is part of the answer.
And if there is dry air present at mid-levels, the condensation of rising air from near the surface doesn't happen (imperative), heat isn't released into the surrounding air, the heat engine that we know as a TC doesn't happen.
Dry air in a TC is not unlike injecting a little water in the fuel lines of an auto.
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Quoting nishinigami:
My link didn't work before... sorry.
Link


that loop makes it look like Erika is headed to south america
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yup
Member Since: December 9, 2008 Posts: 0 Comments: 2498
My link didn't work before... sorry.
Link
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Quoting msphar:
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.


Miami, like San Juan, and pretty much all cities, is also surrounded by extensive suburbs. The population of the metro Miami area is about 5.5 million. It's always a mistake to look at the size of the main city and assume that it is the whole metro population.
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Quoting CaneHunter031472:


On that note Erika RIP....

ERIKA will be RIP someday.
Thats a sure bet.
But i give Erika 10more days.
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Quoting szqrn1:


:) thanks! will check back later... quess they don't pay me to stay here on this site! too bad!


the odds of it making it into the GOMEX are fairly slim, and the odds of it being powerful in the GOMEX are even slimmer, imo
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nope
Member Since: December 9, 2008 Posts: 0 Comments: 2498
AMY!!!!!
Member Since: December 9, 2008 Posts: 0 Comments: 2498
Quoting btwntx08:

possibly


:) thanks! will check back later... quess they don't pay me to stay here on this site! too bad!
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SQUAWK!

:)
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Sydney CBD at 5PM today from North Head.
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agree
Member Since: December 9, 2008 Posts: 0 Comments: 2498
Quoting IKE:


I won't. Some will call you a downcaster. I've been labeled that a few days ago.

You're entitled to your opinion.


On that note Erika RIP....
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There's no such thing as a downcaster it is just a word made up by wishcasters for the forecasters that actually tell the truth
Member Since: August 29, 2006 Posts: 22 Comments: 1352
Quoting atmoaggie:

Could be the dry air is changing the usual profile? I really don't know. I'll admit it.


alright, well i dont know if anyone knows. we have had some really odd systems this year
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nope
Member Since: December 9, 2008 Posts: 0 Comments: 2498
Quoting btwntx08:
wow she's blowing convection right at the center


Who's convection?
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Quoting tornadodude:


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

Could be the dry air is changing the usual profile? I really don't know. I'll admit it.
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232. Relix
Oh oops accidental Post.
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Quoting apocalyps:


gOING TO THE CARRIBBEAN;
dRIFTING west
wEAK SYSTEM THE COMING DAYS
EXPLODE ON SUNDAY


GOMEX bound??
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Quoting jpsb:
I'm surprised it's held this long! But even after the front lifts the trof will still be around protecting the GoM. If you are on the GoM, the thing to watch is that HUGE trof on the east coast. When that goes away then CV storms have a chance of reaching the GoM.

Now if I were gulfcasting, lol, I say that since Erika is not stacked, (circulation wise that is, lol) she remains unorganized and she might just slide under the upper level steering currents (trof as it lifts and moves east) and continues slowly west, maybe even a little south of west. Then she organizes and makes it into the GoM after the front has lifted.

the above is not likely as Erika is bond to become better organized and the trof is exceptionally strong. Any movement north makes interaction with that trof more certain. Any interaction with Island mountains will likely rip a weak T.S. like Erika apart. So if Erika stays weak and continues west the islands will get her. If the gets strong and goes more north the trof will get her. Shes got one hard road ahead of her if she wants to get into the nice warm gulf waters.

Thank you for that fine explanation. Makes sense to me.
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Quoting szqrn1:
hey goodmorning guys! I havent been here for a couple of days and logged on to see that potentialy bad girl down there!!! what's her story? where is she going? at work so can't spend too much time.. somebody give me the short and sweet (or not so sweet) of it? I am on Ms coast... thanks!!


gOING TO THE CARRIBBEAN;
dRIFTING west
wEAK SYSTEM THE COMING DAYS
EXPLODE ON SUNDAY
Member Since: Posts: Comments:
226. IKE
Quoting tornadofan:


So, will people still yell at me if I say RIP?


I won't. Some will call you a downcaster. I've been labeled that a few days ago.

You're entitled to your opinion.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
224. Relix
Quoting tornadofan:


So, will people still yell at me if I say RIP?


I won't go ahead. It's a 50/50 chance now.
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Quoting tornadofan:


So, will people still yell at me if I say RIP?


YELL! jp, well it is a possibility that Erika is dying, but, i wouldnt count her out until she is completely gone, you know?
just playing it safe
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Quoting OSUWXGUY:
Sounding from 8AM EDT from Saint Marten.

Not 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.



Yeah, and because of this I have steered clear of trying to forecast the track. I am focusing on more about the structure of the storm watching for a pronounced organization phase to set in. This has kept me less frustrated than most I have seen. I am not making any best guesses until I know the models can get a better handle on things with a definite tropical cyclone.
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hey goodmorning guys! I havent been here for a couple of days and logged on to see that potentialy bad girl down there!!! what's her story? where is she going? at work so can't spend too much time.. somebody give me the short and sweet (or not so sweet) of it? I am on Ms coast... thanks!!
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Quoting OSUWXGUY:
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


So, will people still yell at me if I say RIP?
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218. IKE
Quoting AussieStorm:

That always happens. Waste of water.


And it hadn't rained since last weekend. Oh well..I washed the mud off.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting IKE:
Can anyone really blame the NHC for their outlook?


Poor TS Erika, shear is trying to have her for lunch, if she keeps blowing up with convection and if sheer decreases, everybody watch out!!
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Quoting Patrap:


Kinda Like Cracker-Jack Candy,..we may get a Surprise



So the same trough that could protect the GOM from Erika may leave a little something behind for us?
Member Since: September 5, 2007 Posts: 0 Comments: 3488
Quoting WeatherStudent:
Die, yeah right!


You made the offer...I'm just saying. You know how people feel when you welsh a bet...
Member Since: August 2, 2006 Posts: 10 Comments: 9922
who's the female version of JFV/WS? Maybe they could do a blog together....
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Quoting OSUWXGUY:
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

Dang, I spent some time looking for this. Thanks for putting it up! (forgot all about the Wyoming sounding page)
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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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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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