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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1320. Grothar
Quoting TampaBayStevo:
Could someone please just tell me if these wind sheer links are working for them?

http://tropic.ssec.wisc.edu/real-time/windmain.ph p?&basin=atlantic&sat=wg8∏=shr&zoom= &time=

They no longer work for me, and I dont know if my PC has something wrong, or if I need new links.


Try this:

Link
Member Since: July 17, 2009 Posts: 71 Comments: 26117
Quoting robj144:


No you guys are right.. that's why I erased my comment, but everyone is quoting my erased comment. Thanks a lot. I was trying to save myself the embarrassment. :)


Too late. lol
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Quoting AegirsGal:
Just registered for membership, but I have been a lurker for ages. Emily is full of surprises, chugging right along, oblivious to our forecasts, and the models.
Emily has had internet connectivity problems, so she isn't getting the updates from the forecasters
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Quoting ElConando:


Not entirely sure. I know NW movement is at 315 Degrees because its splits the difference between 270 and 360. And I'd think WNW movement would bet the average between 270 and 315. But I may be doing that wrong.

You are correct !!
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1315. robj144
Quoting ElConando:


Not entirely sure. I know NW movement is at 315 Degrees because its splits the difference between 270 and 360. And I'd think WNW movement would bet the average between 270 and 315. But I may be doing that wrong.


No you guys are right.. that's why I erased my comment, but everyone is quoting my erased comment. Thanks a lot. I was trying to save myself the embarrassment. :)
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Quoting HurricaneSwirl:
Welp, 18Z GFS kills Emily over the eastern tip of Cuba.
Now that wouldn't be no fun :(
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Re: #1284, thanks, HH27. I have indeed been here a long time, mostly lurking. Have learned so much from this site, and over the years used the various satellite/radar views here to spot storms "straying" from their projected paths in time to buy myself precious preparation time!

The bickering and silliness on this Blog of late, doesn't change for me that it's my most valuable site for tropic-weather info. Moreover, I think it performs a valuable service for a vast number of people. It's well worth my few bucks a year to support.

Thanks for being here!
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Quoting TampaBayStevo:
Could someone please just tell me if these wind sheer links are working for them?

http://tropic.ssec.wisc.edu/real-time/windmain.ph p?&basin=atlantic&sat=wg8∏=shr&zoom= &time=

They no longer work for me, and I dont know if my PC has something wrong, or if I need new links.


Here... Link
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1311. Seastep
Quoting TampaBayStevo:
Could someone please just tell me if these wind sheer links are working for them?

http://tropic.ssec.wisc.edu/real-time/windmain.ph p?&basin=atlantic&sat=wg8∏=shr&zoom= &time=

They no longer work for me, and I dont know if my PC has something wrong, or if I need new links.


Just go to the base url http://tropic.ssec.wisc.edu/

And then hover over the basin and select Winds and Analysis.
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Quoting HurricaneSwirl:
Welp, 18Z GFS kills Emily over the eastern tip of Cuba.


I wouldn't doubt it. Water vapor shows quite a bit of southerly shear still ahead of Emily and she's already really struggling. By the way, the mountains over eastern cuba aren't a walk in the park.
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Quoting robj144:


Wouldn't it be halfway between North (0 or 360 Degrees) and West (270 Degrees), so 300 degrees is exactly WNW?


Not entirely sure. I know NW movement is at 315 Degrees because its splits the difference between 270 and 360. And I'd think WNW movement would bet the average between 270 and 315 which is 292.5 or 293. But I may be doing that wrong.
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1306. Grothar
Member Since: July 17, 2009 Posts: 71 Comments: 26117
That's a mess of a tropical storm...

Member Since: August 16, 2007 Posts: 6 Comments: 12461
gfs 48 hrs

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Quoting TropicalAnalystwx13:


Here comes the RIPing.


Which is very possible, especially if she spends any length of time over it.
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1302. robj144
Quoting charlottefl:




Yes, I read too fast... you are correct.
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I find it interesting that storms seem to form subtropically a lot easier in the WPAC.
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Could someone please just tell me if these wind sheer links are working for them?

http://tropic.ssec.wisc.edu/real-time/windmain.ph p?&basin=atlantic&sat=wg8∏=shr&zoom=&time=

They no longer work for me, and I dont know if my PC has something wrong, or if I need new links.
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Quoting Jedkins01:



Well I am going to school for meteorology, and there is so much we learn about the atmosphere, and I am just getting started. I think we are too expected to follow the computers every move rather than using our education to make our own judgments when the computers are obviously off. I have seen the NHC do it before, but to me it appears that there are less forecasters that think for themselves and too many that follow model protocol.

Computer models are designed to solve all the massive amounts of equations in a short time and create forecast plots to help us understand what might occur in the future, but the models were not designed to do the forecast for us, so that we must follow the models always. Like I said, we shouldn't throw them out the window, that is just stupid, they are a huge aid to meteorologists. But there is a fine line between using models to help make a forecast and following everything they do.

I mean, I'm not trying to be critical at all, Ive just always been a "outside the box" kind of person.

On the other hand, maybe there's a lot yet I don't understand that goes into play once you have a job as a meteorologist and lives and property are at stake based on what I or my peers forecast.

Maybe the situation of being a professional meteorologists just is a completely different situation and I would be just as conservative. Maybe they want to make sure they don't take on the "boy who cried wolf" appearance that weather forecasters have been looked at for being quick to forecast a change.

I don't know, I don't want to be a know it all, or act like I have better solutions, I'm just talking, and there is much more knowledge and wisdom to acquire in my life as I get older, I am only 20, after all.
I say we set up an experiment. Every day the meteorologists with computer aid give their forecast. A few minutes later the computer only forecast is released and they are compared side by side. If the computer only forecasts are more accurate then we can FIRE THE WHOLE BUNCH AT NHC and let them join this blog or whatever.
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Quoting robj144:


Wouldn't it be halfway between North (0 or 360 Degrees) and West (270 Degrees), so 300 degrees is exactly WNW?


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1295. Grothar
Member Since: July 17, 2009 Posts: 71 Comments: 26117
Quoting HurricaneSwirl:
Welp, 18Z GFS kills Emily over the eastern tip of Cuba.


Here comes the RIPing.
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Quoting chevycanes:
gfs at 39 hrs.

There she goes...
Member Since: December 1, 2006 Posts: 2 Comments: 3619
1291. robj144
Quoting ElConando:


Moving about 280 degrees to the West to be exact so North of Due west. I think 290 or 295 is the threshold for WNW movement.


Sorry... wrote something and then erased it.
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Welp, 18Z GFS kills Emily over the eastern tip of Cuba.

EDIT: It might be coming back from the dead just to the north of Cuba at 48 hrs

EDIT 2: Wait no, it dies again at 54 hrs. (probably didn't have to do anything to do with Emily in the first place)
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Quoting tiggeriffic:


but according to a lot of the data, Emily isnt stacked enough to really feel it...even the mets on TV said that all the models predicted emily would be stronger by now to be affected...


We'll just have to see. No, Emily is still not stacked. For the record, I think the NHC track is a little too far to the east and that Florida is very much in the bulls eye. However, Emily should still feel the effects of the weakness to the NW of her, stacked or not.

Also, the slow down in forward speed should be an indication that she's about to change directions.
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18z GFS shows some decent vorticity with the African coast wave, however weakens it fairly quickly.
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Quoting hurricanehunter27:
Good 2 know im not the only one seeing it, btw nice to see sombody who has been on the blog for 9 years.


See it, just not sure what it is...llc or mlc?
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Quoting OrchidGrower:
HH27 - post 1264 - I saw it, too; slight jog WSW
Good 2 know im not the only one seeing it, btw nice to see sombody who has been on the blog for 9 years.
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Quoting HurricaneHunterJoe:


Eyewall of Typhoon Muifa on top of Okinawa


Okinawa web cams
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Quoting FLWeatherFreak91:
It's definitely somewhat north of west, but not much.


Moving about 280 degrees to the West to be exact so North of Due west. I think 290 or 295 is the threshold for WNW movement.
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LLC almost completely under the convection.
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Quoting K8eCane:


Theres a lot of money in them hotels and motels and restaurants etc


The internation dragonboat races are in Tampa,Fl this year. So this storm, should it move further west, will make it interesting for the folks in Fl for this event.
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1279. HadesGodWyvern (Mod)
Japan Meteorological Agency
Tropical Cyclone Advisory #8
TROPICAL STORM MERBOK (T1110)
6:00 AM JST August 4 2011
==========================================

SUBJECT: Category One Typhoon Near Minami tori shima

At 21:00 PM UTC, Tropical Storm Merbok (1000 hPa) located at 23.9N 158.8E has 10 minute sustained winds of 35 knots with gusts of 50 knots. The cyclone is reported as moving west northwest at 6 knots

Dvorak Intensity:

Gale Force Winds
=================
200 NM from the center in north quadrant
150 NM from the center in south quadrant

Forecast and Intensity
========================
24 HRS: 26.0N 156.9E - 45 knots (CAT 1/Tropical Storm)
45 HRS: 28.5N 155.6E - 50 knots (CAT 2/Severe Tropical Storm)
69 HRS: 31.0N 155.6E - 55 knots (CAT 2/Severe Tropical Storm)
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Quoting PcolaDan:


So, I would be a better person in the heat if I lose my P. ;>)
that depends on your level of hydration...
Member Since: August 16, 2007 Posts: 6 Comments: 12461
Quoting charlottefl:
CURRENT STEERING:






3 HOURS PREVIOUS:



6 HOURS PREVIOUS:



Ridge building westward.
not only that trough is lifting out or at least flattening out.
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I have lurked for several years, time to join the fun and learn. The NHC still assumes my moniker in their 5pm discussion. I like that.
Emily seems to be giving the models a bit of a fit. I read on this blog, "you can't trust xyz model because of this or that" and "xyz has a tendency to always keep the storm xyz direction". Is there a site that tracks model accuracy?

Hat tip to DestinJeff for username suggestion yesterday.
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gfs at 39 hrs.

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Quoting atmoaggie:
Really, I doubt it to be drastically different.
Hopefully the improvement is real, though.

A thought about that, though, is that these models are always being upgraded and biases changing. Coherently using them as guidance in a forecast situation requires us to be informed as to the changes and their effects. Otherwise, in this particular case, some forecaster would possibly account for a bias in the HWRF (they maybe had noticed in past situations) that no longer exists in it's current form.


Somewhere I remember reading about those improvements in the preseason, I wonder if the SDM was just repeating the same. It had a major updrade earlier in the year, and this may have been a bug fix. I will take it at face value though.
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Link

Check this out. Look SW of the position marker. Is that the LLC or did Emily become decoupled yet again? Click on 1km vis and animate...
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Honestly I'm just waiting for it to take a small dive to the south and see the blog freak out.
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Quoting BahaHurican:
I don't see much change in the forecast. This is one of the times when putting the line in between the dots helps. Basically that line has stayed on one side or the other of New Providence - the little island between Andros and Eleuthera - all day.

There's been more change at the bottom end of the cone
For which the Turks and Caicos are extremely thankful!

but other than that, no real change seen.

I am waiting, as, I am sure, the NHC forecasters, to see how the G-IV info impacts the model performance.
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Quoting MississippiWx:


The weakness hasn't changed much the last 6 hours or so. It's there and she has finally reached a longitude where it will effect her.


but according to a lot of the data, Emily isnt stacked enough to really feel it...even the mets on TV said that all the models predicted emily would be stronger by now to be affected...
Member Since: September 16, 2007 Posts: 0 Comments: 3650

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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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