WunderBlog Archive » Category 6™

Category 6 has moved! See the latest from Dr. Jeff Masters and Bob Henson here.

High wind shear disrupts Emily as it approaches Hispaniola

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

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.



The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

Reader Comments

Howdy, everyone. Just came in and am trying to catch up. I see that Emily has been nearly stalled for several hours. Has she taken advantage of this and begun to upright herself? I know that her LLC has been far west of the MLC throughout her life so far.
Quoting ShenValleyFlyFish:
If all the lurkers and folks who aren't posting right now who have logged in at once it would probably crash the site. I fail to see how "going through a cat 5" gives one extra insight as to understanding scientific data.

Nope but it will defently give one insight and understanding of term OooH S%$# .
Just as a side note with this storm, you can probably expect the forecast track error to be as much as double the normal track error with all the uncertainty at this point, just something to keep in mind.
Quoting EYEStoSEA:
Thank u 4 the WV imagery... to me the trough is so clear there... that's when I began to understand why the NHC was harping on that Wed night turn. It wasn't so much Emily they were confident in as that trough....
Quoting katadman:
Howdy, everyone. Just came in and am trying to catch up. I see that Emily has been nearly stalled for several hours. Has she taken advantage of this and begun to upright herself? I know that her LLC has been far west of the MLC throughout her life so far.

Now the question is when movement resumes to we get a tilt a whirl again?
Quoting hurricanehunter27:
Agreed almost no model can handle this storm! But she is a closed LLC 1003mb.

I get the point, but I am sure if you think back over the years many storms in this position with a turn expected to occur near or south of Haiti seem to play games. It historically is a tuff area to forecast. When the forecast called for a turn north across Haiti, I kinda expected a guessing game as to when and exactly where it would happen. Haiti and the surrounding area always seems to create many surprises when systems approach, likewise as storms approach eastern cuba from the south.
Quoting MiamiHurricanes09:
Would be nice if they played some real teams for more than half the season. Furman, Florida Atlantic, Vanderbilt, etc... are jokes.

Anyways, back to Emily, lol.
SEC ACC Nuff said!
Quoting doabarrelroll:

Unless you were bron before 1935 and lived in Florida and Louisiana that is unlikely as only 3 cat5's have hit the US in the last 100 years. I do belive you are an American right?
you have two now for the third?
It should be noted that I am not noticing the ULAC ripping off the northern clouds that i was seeing north of Emily earlier yesterday. Convection is growing with Emily and it looks to me like her environment is improving. We might be finally starting to see the "stronger" Emily. She has stayed at 50 MPH but I think she will soon be a hurricane; perhaps in the next 24 hours if she can move just a little further west. The DR would be a problem if she got to close.


Quoting blsealevel:

Nope but it will defently give one insight and understanding of term OooH S%$# .

I had the opportunity to do damage assessment following 2 Cat 5s (Mitch - Honduras and Andrew - at Homestead Air Base). One was mostly water event (landslides and flooding) and the other was a wind event.

What I learned is that hurricanes are very dangerous and people need to take them seriously. Property damage can be terrible and disrupt people's lives. But the loss of life is tragic and often could have been avoided.

I hope people take hurricane warnings seriously and protect themselves first - and worry about property second.

This is an excellent forum for helping all of us better understand the threat that hurricanes - and even tropical storms pose.
Misposted on an obso blog
Good Nights everybody. Til tomorrow
Starting to look like Miami might get this one. She was stalled or drifting and now convection is right over the LLC and she should strengthen and get pulled more NW. Originally I thought this system would move towards SW florida overall and have some land interaction with Cuba.
Quoting HurricaneSwirl:

No, he's right. 280 is just north of due west. 270 is due west.
stay at 280 no further north
come west dear emily
Evening all, so has Emily begun a legit turn north? Or is she still defying the NHC?
Hurricane Eugene’s cloud top temperature surround the eye has continued to warm slightly over the past several hours. It indicates that it should be at peak intensity and weaken pretty soon as it starts to head over cool SSTS. Its structure has a somewhat annular hurricane like-appearance with a large eye.