High wind shear disrupts Emily as it approaches Hispaniola

By: Dr. Jeff Masters , 5:06 PM GMT on August 03, 2011

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In defiance to its forecast, Tropical Storm Emily continues to move due west this morning, and we wonder just how far west it will get before turning toward Hispaniola. Recent Hurricane Hunter missions have shown that Emily is still very poorly organized, and although the center of circulation is plainly obvious on satellite imagery, it's only because it is so displaced from the thunderstorm activity. Wind shear around the storm is just high enough, around 20 knots out of the west, to push the upper levels of circulation and thunderstorm activity to the east, exposing the surface low. In order for tropical cyclones to intensify (or, continue to exist at all), they need to be vertically stacked and standing straight up in the atmosphere. Right now, Emily is tilting to the east. This is bad news for the organization of the storm, and something that Emily will have to work hard at recovering from. In addition to the wind shear, dry air continues to wrap around the north and west of the storm. This isn't as critical as unfavorable wind shear, but it's not helping to create new thunderstorm activity. The strongest winds of 50 mph were found to the north and east of the center this morning, and Emily is not expected to intensify before making landfall in Hispaniola, which is forecast for tonight. The HWRF is forecasting the strongest precipitation to fall on the northeast side of the storm as is passes over Hispaniola. This is relatively good news for Haiti, but the country could still receive up to 5 inches of rain, and since the models have been trending the track west over the past couple of runs, it's something to watch closely. No matter the scenario, Emily is expected to produce heavy rains, flash flooding, and mudslides in Haiti and the Dominican Republic, which are all to common on the mountainous island.


Figure 1. Forecast precipitation accumulation from the HWRF high resolution model's 6Z (2am EDT) run. The color contour scale is in inches. The coastlines are a thin, red line. The Dominican Republic is expected to get the most rain out of Emily. You can view the HWRF model runs on Wundermap.

Forecast for Tropical Storm Emily
The future of Emily remains uncertain, and even the National Hurricane Center is using the "if" word when forecasting Emily's track after crossing Hispaniola. "If" it makes it north of Hispaniola. Over the past couple of runs, the models have been trending their forecast tracks back to the west, most likely because Emily has remained on a westward track longer than expected. This is expected—the longer Emily remains shallow and unorganized, the longer it will track west. It will need to build up taller in the atmosphere to be influenced by the steering winds that can push it north. Given its westward track, today's models are likely closer to reality than what we've seen in the past couple of days. This morning, the CMC, UKMET, and HWRF models send Emily on a northwest track to Florida. This is a change from the past couple of days for the HWRF, but the CMC and UKMET have consistently been the western boundary of model consensus. THE GFDL has also taken a huge swing to the west, and now suggests it will come very close to a southeast Florida landfall. The ECMWF and GFS continue to forecast that Emily will take a harder turn north through the Bahamas, not reaching the Florida coast.


Figure 2. Satellite image of Tropical Storm Emily at 11:15am EDT. The surface circulation is visible to the west of the strongest thunderstorm activity.

Consensus of the models falls between the HWRF/GFDL solution and the ECMWF/GFS solution, and the National Hurricane Center continues to use the consensus for the official track forecast, which calls for Emily to take a turn to the northwest and make landfall in Hispaniola this afternoon, after which continuing northwest until Saturday morning when it's between the island of Grand Bahama and West Palm Beach, Florida. At this point, they expect the storm to jog north and then northeast.

Emily's intensity forecast continues highly dependent on the track it takes. Assuming it can survive the wrath of Hispaniola, Emily will enter slightly more favorable environmental conditions to the north of the islands. This is what the Hurricane Center is forecasting, although they remain cautious. There is a very good chance that, if Emily does turn northwest today, it will not be able to reorganize after crossing Hispaniola. If it does maintain organization, Emily could reach hurricane strength as it moves northeast out to the open Atlantic. The other scenario at this point is that the storm keeps moving west, which will be detrimental to its orgnization. The models that track Emily into the far eastern Gulf of Mexico don't suggest any reintensification—the CMC fizzles the system below tropical storm strength quickly, probably because of the long track over Cuba it would have to take. In any case, Emily remains a threat most certainly to Hispaniola, and potentially to Florida.

I'm planning a quick update later this afternoon/evening for an update on new model runs, and potential Hispaniola landfall.

Angela

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Emily appears to be slowing down within the last couple of hours. This could signal that her turn to the northwest may be coming soon.
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Quoting yonzabam:


Drak, I know you know your stuff big time, but there's always a wave coming off Africa.

There was one a couple of days ago that was being called 'Franklin' on here. What happened to it?

Not saying that you shouldn't flag up waves coming off Africa. The one reason I don't put Jason on ignore is that he keeps us well informed about these waves with his images (thanks, Jason).

No idea what percentage of waves coming off Africa that are flagged up on here actually develop into tropical storms, but I'd intuitively put it at about 15%.

What would you put it at?


Just keeping everyone informed. I would give about the same percent as well.
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Quoting Jedkins01:


Well considering Emily isn't moving towards the mountains of Haiti right now, I don't think that will be an issue at all :)

couldn't have said that any better....lol
Member Since: September 18, 2010 Posts: 0 Comments: 5248
Quoting BahaHurican:
Was about to say we've been looking at that since this a.m......


That's because you're nice, Baha!
Member Since: July 17, 2009 Posts: 71 Comments: 27210
to me looks like the 5Pm advisory will remain the same except a lower pressure and the forecast cone will remain the same also. IMO
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Quoting Drakoen:
I know everyone is fixed on Emily but there is an very impressive wave just off the coast of Africa.




Drak, I know you know your stuff big time, but there's always a wave coming off Africa.

There was one a couple of days ago that was being called 'Franklin' on here. What happened to it?

Not saying that you shouldn't flag up waves coming off Africa. The one reason I don't put Jason on ignore is that he keeps us well informed about these waves with his images (thanks, Jason).

No idea what percentage of waves coming off Africa that are flagged up on here actually develop into tropical storms, but I'd intuitively put it at about 15%.

What would you put it at?
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Quoting Drakoen:
Emily is not just battling 20 knots of shear. She is encountering dry air in the mid and upper levels of the atmosphere which is amplifying her disorganization.


She better skirt under the islands or risk losing everything, because she won't even be able to get any convection going over 10,000 ft.
Member Since: December 1, 2006 Posts: 2 Comments: 3634
Quoting Drakoen:
Emily is not just battling 20 knots of shear. She is encountering dry air in the mid and upper levels of the atmosphere which is amplifying her disorganization.



That sounding is out of the DR?

Edit: Nm, I see the lat/lon now. Santo Domingo DR
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Quoting SWLACajun:
Drakoen, isn't that alot of dry air above and below the new wave off Africa? Would it have problems shooting the gap as it crosses?

No, the dry air is far enough away in either the poleward or the equatorward direction to not have an impact on the wave.
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Quoting Tropicsweatherpr:


The question Levi and Drakoen is if it will survive the long journey in the Atlantic.
There is a LOT of SAL dust out there...
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Quoting BahaHurican:
Wow... didn't realize they were staging from here... could have gone down 2 the airport to see the plane.



They left from Tampa, that was just the first dropsonde location.
Member Since: September 23, 2005 Posts: 15 Comments: 11343
Quoting kmanislander:


See my post 648


Hey KMan, good to see ya. what do u think about Emily, been sitting back reading all day, hardly post anymore.

sheri
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Emily is not just battling 20 knots of shear. She is encountering dry air in the mid and upper levels of the atmosphere which is amplifying her disorganization.


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TS.Emily's travel-speed was 15.7mph(25.2k/h) on a heading of 278.6degrees(West)

Copy&paste 15.3n63.6w, 15.6n64.9w-15.9n66.3w, 15.9n66.3w-16.3n67.7w, 16.3n67.7w-16.6n68.9w, 16.6n68.9w-16.8n70.3w, ctm, kin, 16.6n68.9w-17.63n77.17w, 16.6n68.9w-18.45n87.77w into the GreatCircleMapper for more info

Using straightline projection of the travel-speed&heading derived from the ATCF coordinates for 12pmGMT then 6pmGMT :
TS.Emily was headed toward passage over Chetumal,Mexico ~3days from now
after passing 5.5miles(8.9kilometres) south of Jamaica ~1day3hours20minutes from now
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Quoting Grothar:


I've been posting images since last night and no one has commented. They just don't care. :)



They all look great coming off Africa! Then we get to the real world over here,with almost all of them having to fight for their lives due to one thing or another. I do like the posts and pics, keep em coming!
Member Since: September 18, 2010 Posts: 0 Comments: 5248
Drakoen, isn't that alot of dry air above and below the new wave off Africa? Would it have problems shooting the gap as it crosses?
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MJO 15 Day forecast.


NAO forecast.
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Quoting Grothar:


I've been posting images since last night and no one has commented. They just don't care. :)

Was about to say we've been looking at that since this a.m......
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Quoting BahaHurican:
It can't be that hard to understand; FL east coast event = Bahamian event. Emily can't get to the ECFL without passing through the Bahamas!

Now if u mean W coast FL, I'd appreciate the clarification....


But, it is possible to have a Bahamian event without an ECFL event.
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CycloneUK...u have mail
Member Since: September 16, 2007 Posts: 0 Comments: 3666
dang convection juts keeps on fireing wonder why
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Link

The latest 2 p.m. models show the consensus with Emily coming ashore in Deerfield Beach and making the turn and exiting at St. Lucie Inlet.
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Emily is leaving the subsident regime of the Caribbean east of 75.
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The 12z ECMWF mimics the 0z in looking for trouble in 10 days or so from Cape Verde origin.

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MIMIC-TPW shows very high values of Precipitable Water values over the Eastern Atlantic:


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Quoting ncstorm:
does the psychic twins prediction come to anyone's mind about the east coast storm?



Their prediction is for the Fall and specifically a major Cat 4 or 5 cane. September material, IMO.
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I am with you on finding COC to SW stormpetrol
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Instead of braille, how about Morse code, looks better in type ...- - - ..- -
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Quoting Grothar:


I've been posting images since last night and no one has commented. They just don't care. :)



I noticed it yesterday and it did indeed look impressive. Surprised it didn't get any attention too.
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And still moving west...
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Quoting Bretts9112:

I give the NHC a thumb up for that pretty amazing to get the time right.


They're often really good with timing and track but not so much with intensity.
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Quoting Hurricanes12:
Levi, do you expect Emily to be a Florida coast event, or a Bahamian event?
It can't be that hard to understand; FL east coast event = Bahamian event. Emily can't get to the ECFL without passing through the Bahamas!

Now if u mean W coast FL, I'd appreciate the clarification....
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Kinda surprised the NHC didn't give that area just off the African coast a probability... I would say at this point 40% chance in 48 hours. That thing is looking nice... Hello Cape Verde Season...
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Quoting Tropicsweatherpr:


The question Levi and Drakoen is if it will survive the long journey in the Atlantic.


Tropical waves need to be given at least 24 hours after coming off of the African coast to see if the new ocean-based dynamics will allow them to continue firing convection as they transverse the eastern and central Atlantic.
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Upper level anticyclone just to the east of the wave with the upper ridge axis expanding over:


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Quoting Drakoen:

lol yeah its hard to with Emily out there. Very well structured wave and upper level winds appear favorable for some development of the system.



Yup.



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does the psychic twins prediction come to anyone's mind about the east coast storm?
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Quoting Seflhurricane:
more than likely the NHC will issue tropical storm warnings for the central bahamas and a tropical storm watch for the northwestern bahamas . IMO
The NHC should start thinking about posting tropical storm watches for the Keys and South Florida. Although they aren't within the watch time frame so we won't see that yet.
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It appears that the new thunderstorms firing up near the center are encountering wind shear still....One thing is for sure is Emily still trying!!!! Going to make it hard for the steering currents to pick up the storm and move it to the north...
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Quoting Levi32:


Floater just got switched to it. There appears to be some vorticity associated with it.



The question Levi and Drakoen is if it will survive the long journey in the Atlantic.
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HH just made a turn back toward the Vortex. Let's see if the next reading holds at 1003 like the last.
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Quoting zawxdsk:


The GFS and NAM solutions on here make it look like they are redeveloping the center of circulation further to the south. Levi was pointing out that recon is still finding lowering pressure that way.

Still think we are going to see a new center once that first starts to hit the mountains - even if in the windward passage. Don't discount them - they are tall!


Exactly..
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Quoting Grothar:


I've been posting images since last night and no one has commented. They just don't care. :)

lol yeah its hard to with Emily out there. Very well structured wave and upper level winds appear favorable for some development of the system.
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Quoting TropicalAnalystwx13:
I find highly unlikely that Emily will dissipate over the mountains of Haiti. The circulation is well-defined, as we saw when it was exposed. What it needs to do though is get stacked with its MLC, which it probably wont do until after it crosses the island and enters the Bahamas.

May briefly become a tropical depression as it crosses, but the intensity should pick right back up under very favorable conditions.


Well considering Emily isn't moving towards the mountains of Haiti right now, I don't think that will be an issue at all :)

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Quoting HurricaneHunterJoe:
Emily LLC still firing off thunderstorms and they still getting sheared off the center,but alive she is and trying hard. looks like she will mis Hispaniola all together unless she hooks hard right,something she has shown no tendency to do.

I watched Levi's Tidbits and feel that he pretty much has it right. Looks like Florida for landfall to me, and I'm picking the west coast town of Bonita Springs as the bullseye so to speak. It may parallel to the southwest florida coast for a bit and hit land with a heading of NE Or ENE, As a Tropical Storm Or Cat 1/Minimal Hurricane.

JMHO


I'm picking Myrtle Beach, SC.
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Quoting Drakoen:
I know everyone is fixed on Emily but there is an very impressive wave just off the coast of Africa.




Floater just got switched to it. There appears to be some vorticity associated with it.

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Quoting Grothar:


I've been posting images since last night and no one has commented. They just don't care. :)

Quite the impressive image Gro.
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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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