Intensifying Hermine closes in on the Texas/Mexico coast

By: Dr. Jeff Masters , 9:47 PM GMT on September 06, 2010

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Steadily intensifying Tropical Storm Hermine is closing in on the coast near the Texas/Mexico border, and should move ashore late tonight. Hermine became a tropical depression at 11pm last night, and could become a minimal hurricane by 11 pm tonight. Hermine's rate of intensification from nothing to a strong tropical storm is one of the fastest on record. It turns out that the extreme southwestern Gulf of Mexico's Bay of Campeche, where Hermine formed, is prone to these sort of rapidly intensifying tropical storms. The curvature and topography of the land help induce a counter-clockwise spin to the air over the region, which helps get tropical storms spinning up unusually quickly. Helping the spin-up process are the very warm 30°C waters, low 5 - 10 knots of wind shear, and moist atmosphere. Hermine promises to be a very wet storm, and latest long range radar out of Brownsville, Texas shows a large area of heavy rain has been drenching southern Texas and northern Mexico all afternoon, with radar estimated rainfall amounts exceeding two inches in a few areas along the coast. Radar loops show that an eyewall is attempting to form, but a region of dry air from over land spiraled into Hermine's core between 4 - 5pm EDT, disrupting eyewall formation. However, it now appears that Hermine has closed off its eye from this dry air, which should aid in intensification. Satellite imagery shows Hermine has vigorous thunderstorms with very cold tops, and improving low-level spiral banding.

Forecast for Hermine
Hermine doesn't have much time over water before it comes ashore, which is a good thing. The storm is steadily organizing, and has a shot at reaching hurricane strength before the center moves ashore late tonight, near midnight. Heavy rain will be the main threat from Hermine, though isolated tornadoes may also cause damage, particularly over South Texas. Hermine is expected to accelerate through Central Texas Tuesday and Wednesday, and the storm's rains will help alleviate moderate to severe drought conditions affecting Central Texas.


Figure 1. Late afternoon radar image of Tropical Storm Hermine. Note the band of dry air spiraling into the core of the storm from the north.

Gaston continues to suffer from dry air
An Air Force Hurricane Hunter aircraft spent the afternoon in Gaston's remains, and found a weak 1012 mb center of low pressure with only a limited region of westerly winds on the south side of the center of circulation. Top surface winds uncontaminated by heavy rain seen by their SFMR instrument were in the 30 - 35 mph range. The airplane found plenty of dry air in the storm's environment, and there are not enough heavy thunderstorms in ex-Gaston's circulation for it to qualify as a tropical depression. The remains of Gaston are now approaching the northern Lesser Antilles, and residents can expect a few heavy rain showers and wind gusts up to 40 mph beginning early this evening and continuing into the night. Latest radar out of Martinique doesn't show much in the way of heavy rain, and satellite imagery confirms that the thunderstorm activity associated with Gaston's remains is quite sparse. A large amount of dry air surrounds Gaston's remains on all sides, as seen on water vapor satellite loops.


Figure 2. Afternoon satellite image of the remains of Gaston, approaching the Lesser Antilles Islands.

Forecast for Gaston
There is little change to the forecast for Gaston's remains. Dry air will continue to be the major impediment to development, and the system is unlikely to become a tropical depression today. However, wind shear, which is currently a moderate 10 knots, is forecast by the latest SHIPS model run to fall very low, 0 - 5 knots, tonight through Wednesday. With almost no wind shear affecting it, Gaston will a better chance of keeping the moisture from its heavy thunderstorms near its core on Tuesday. This will insulate the storm from the dry air surrounding it. The atmosphere is also moister in the eastern Caribbean, further increasing the chances of development. I believe it is probable Gaston will become a tropical depression again on Tuesday. NHC is currently giving Gaston a 70% chance of developing into a tropical depression by Wednesday, which is a reasonable forecast.

Heavy rain showers and gusty winds from the storm will affect Puerto Rico Tuesday morning through Wednesday afternoon. This activity will spread to the Dominican Republic Tuesday afternoon through Thursday morning. Assuming dry air and an encounter with Hispaniola's high mountains do not destroy Gaston, heavy rain from the storm should move over Haiti, eastern Cuba, and Jamaica Wednesday night and Thursday morning. The models don't give much support for Gaston surviving past Wednesday. The ECMWF, GFS, NOGAPS, Canadian, and HWRF models all dissipate Gaston. However, two models--the GFDL and UKMET--predict that Gaston will survive the dry air and an encounter with Hispaniola, and pass far enough south of the island to find a favorable environment in the Central Caribbean for development on Wednesday. Wind shear will be low, water temperatures will be hot, and the atmosphere will be plenty moist. Gaston could intensify into a hurricane in the Western Caribbean by the end of the week, as predicted by the latest run of the GFDL model.

Elsewhere in the tropics
The models are fairly unanimous in predicting development late this week of a tropical wave expected to emerge from the coast of Africa on Tuesday or Wednesday. The next storm will be called Igor.

Next post
I'll have an update in the morning.

Jeff Masters

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Quoting thelmores:


negative...... WNW..... certainly not DUE west.......


I really wonder what people look at when they look at information lol

I think maybe some just chose to see what they want to see lol
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Fujiwha...?
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Quoting PtownBryan:


Well it is not good where it is going in that is for sure. It's Mexico that really needs to worry. But most of Texas needs the rain so while it is a bad thing for others, it is a blessing for some like me. Tropical systems are how we get most of our rain during the yr in se Texas. It's better for this to be a 60 mph ts than an Ike or Rita or Katrina. I pray for the people that go through the bulk of it! I am not a cold hearted guy I promise! I will reword next time!


Oh I understand totally, I am just south of you on the coast. I totally misunderstood the post earlier and I apologize to you.
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I SEE LOTS COULD CHANGE THE FORECAST THE STEERING CURRENTS IN THAT PART OF THE GOM ARE ALWAYS WEAK WHEN A STORM HAS A NORTHERLY COMPONENT..HERMINE COULD END UP GOING IN OVER HOUSTON TEXAS PARALLELING THE TEXAS COAST..
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Quoting Sfloridacat5:
Hermine is coming ashore in Mexico just South of Brownsville (as forecasted by the NHC). I don't see anything changing that forecast.

still 30 mi away not there yet
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Quoting Thundercloud01221991:
the latest recon reading show that the center has moved due west since the last reading


negative...... WNW..... certainly not DUE west.......
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Quoting IKE:
Just a guess....NHC lowers the odds on out-of-Gas-ton?

I think Gast-on has past-on...just kidding..:)
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Quoting FLdewey:
We need the rain.
We're all going to die

It's going North
It's going West

Look at that moisture
Dry air coming into play

Tastes great
Less filling

Ahhh I love das blogg.


Looks like it's moving a little easterly. Maybe a Fujiwhara dance with Gaston is coming up.:)
Member Since: September 10, 2007 Posts: 0 Comments: 11425
78. IKE
Just a guess....NHC lowers the odds on out-of-Gas-ton?

Member Since: June 9, 2005 Posts: 23 Comments: 37860
Quoting TXCaneCrasher:




To PTowBryan - Not really....this is NOT what the Dr. ordered. This is a very bad place for this storm to hit. Not sure why this is being thought of in this way.


Well it is not good where it is going in that is for sure. It's Mexico that really needs to worry. But most of Texas needs the rain so while it is a bad thing for others, it is a blessing for some like me. Tropical systems are how we get most of our rain during the yr in se Texas. It's better for this to be a 60 mph ts than an Ike or Rita or Katrina. I pray for the people that go through the bulk of it! I am not a cold hearted guy I promise! I will reword next time!
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Hermine is coming ashore in Mexico just South of Brownsville (as forecasted by the NHC). I don't see anything changing that forecast.
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Looks like exGaston has one foot in the grave and the other one sliding, but who knows If he hasn't improved by this time tomorrow, I think it might be over for him.
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Quoting Orcasystems:


You missed a Fix somewhere... Pressure is constant on the last two runs.





My bad. The pressure decreased 1mb between the previous vortex message.
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Quoting TexInsAgent:
Tx Cane...he is thinking the Lord for the rain he had in Pearland


Oh, sorry for the misunderstanding.
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If she hadn't slowed down at the last minute, she would have made landfall by now.

Looking from the first advisory, she's approximately 10 to 12 hours ahead of schedule.

Considering how fast she's organised, that's quite important.
Member Since: August 23, 2008 Posts: 7 Comments: 5300
>The study has determined that a local, climatological minimum of tropical
cyclogenesis exists over the eastern Caribbean Sea. This area, known colloquially by
forecasters as the “hurricane graveyard,” is located within the belt of tropical easterlies
during most of the Atlantic hurricane season, which lasts from June through November.
Tropical easterly waves emerging from the African continent usually follow a path
through the Lesser Antilles and into the eastern Caribbean. GOES infrared satellite
imagery shows that easterly waves frequently exhibit warming cloud tops and decreasing
convection in an area bounded by the islands to the north and east, Venezuela to the
south, and roughly 75 degrees longitude to the west. QuikSCAT derived surface winds
during clear-sky conditions frequently show the presence of accelerating easterlies in the
central Caribbean as part of the Caribbean Low-Level Jet (CLLJ). Analysis of the NCEP
global reanalysis wind fields suggests the presence of an area of persistent low-level mass
divergence in the eastern Caribbean. This implies a subsident regime that would weaken
convection. Climatologically, this phenomenon reaches peak intensity in July, then shifts
towards the east and weakens in the latter half of the Atlantic hurricane season. This is
reflected by the local minimum of tropical cyclogenesis points in the National Hurricane
Center’s best track data in the early part of the season. El Niño directly affects the
strength of the CLLJ, and hence, is related to the intensity of the low-level divergence in
the eastern Caribbean. The local minimum of tropical cyclogenesis in this region has
important implications to operational forecasting, since the vast majority of tropical
cyclones in the Caribbean eventually affect surrounding landmasses.

---It seems like Gaston would be less affected by this climate pattern now that it is later in the season.
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Tx Cane...he is thinking the Lord for the rain he had in Pearland
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We need the rain.
We're all going to die

It's going North
It's going West

Look at that moisture
Dry air coming into play

Tastes great
Less filling

Ahhh I love das blogg.
Member Since: August 19, 2008 Posts: 42 Comments: 6269
Quoting MiamiHurricanes09:
Hermine a little bit stronger. Pressure down to 991mb (down 2mb since the last vortex message).


000
URNT12 KNHC 062149
VORTEX DATA MESSAGE AL102010
A. 06/21:20:20Z
B. 24 deg 36 min N
097 deg 03 min W
C. 850 mb 1350 m
D. 50 kt
E. 180 deg 28 nm
F. 277 deg 38 kt
G. 180 deg 30 nm
H. EXTRAP 991 mb
I. 17 C / 1523 m
J. 21 C / 1523 m
K. NA / NA
L. NA
M. NA
N. 12345 / 8
O. 0.02 / 2 nm
P. AF301 0210A HERMINE OB 11
MAX OUTBOUND AND MAX FL WIND 57 KT NE QUAD 21:22:30Z
SLP EXTRAP FROM 850 MB
;


You missed a Fix somewhere... Pressure is constant on the last two runs.





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Quoting angiest:

I had considered that possibility.
Hermine is trying to form an eye.
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weatherguy03 says no way hermine becomes a hurricane...the strongest 65-70 mph winds when it comes inland in 4 to 6 hours...bob has been on top of this since the beginning...good job bob we are glad to have you on here...
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Quoting MiamiHurricanes09:
I agree. If you look on radar, the circulation looks to have turned towards the west (as reflected by Recon) but also slowed down...considerably.


I see a jog west accompanied by very slow movement and some wobbling of the center.
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Quoting DoctorDave1:
Looks like Hermine is making a small loop.

I had considered that possibility.
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La imagen grande:

Member Since: September 10, 2007 Posts: 0 Comments: 11425
Quoting angiest:
Looks like Hermine is slowing to a crawl.
I agree. If you look on radar, the circulation looks to have turned towards the west (as reflected by Recon) but also slowed down...considerably.
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Quoting angiest:
Looks like Hermine is slowing to a crawl.


Not good. :(
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Is it just me or does anyone else think this years names are more creepy than the past?
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Looks like Hermine is making a small loop.
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Looks like Hermine is slowing to a crawl.
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Hermine a little bit stronger. Pressure down to 991mb (down 2mb since the last vortex message).


000
URNT12 KNHC 062149
VORTEX DATA MESSAGE AL102010
A. 06/21:20:20Z
B. 24 deg 36 min N
097 deg 03 min W
C. 850 mb 1350 m
D. 50 kt
E. 180 deg 28 nm
F. 277 deg 38 kt
G. 180 deg 30 nm
H. EXTRAP 991 mb
I. 17 C / 1523 m
J. 21 C / 1523 m
K. NA / NA
L. NA
M. NA
N. 12345 / 8
O. 0.02 / 2 nm
P. AF301 0210A HERMINE OB 11
MAX OUTBOUND AND MAX FL WIND 57 KT NE QUAD 21:22:30Z
SLP EXTRAP FROM 850 MB
;
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Quoting leo305:
Bonnie is a relatively weak system, that didn't even have much rain with it..



Quoting PtownBryan:


Thank the Lord!


To PTowBryan - Not really....this is NOT what the Dr. ordered. This is a very bad place for this storm to hit. Not sure why this is being thought of in this way.
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Quoting Kristina40:


Hermine is NOT relatively weak and quite possibly will be a hurricane when she comes ashore tonight.


Relative to the full spectrum of what a tropical cyclone can be it is rather weak.



That said, flooding rains can still be catastrophic in a weaker system, Hurricane Stan was only a Cat1 and caused over 1,000 deaths in Guatemala, Jeanne killed over 3,000 in Haiti as a TS, and we all know what rains from TS Allison did to Houston.

Luckily, that kind of flooding is not in the forecast with Hermine.
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Right, thanks for the responses.

Kinda amazing how Hermine was moving tail earlier, 3 hours was a whole degree in latitude, yet as soon as she nears land she slows up entirely. She doesn't like it.

Like an anti-Fay.
Member Since: August 23, 2008 Posts: 7 Comments: 5300
Quoting leo305:


when the center touches land, not the eye, the center of the eye


Correct. This is from wiki

Landfall
See also: List of notable tropical cyclones and Unusual areas of tropical cyclone formation
Officially, landfall is when a storm's center (the center of its circulation, not its edge) crosses the coastline.[56] Storm conditions may be experienced on the coast and inland hours before landfall; in fact, a tropical cyclone can launch its strongest winds over land, yet not make landfall; if this occurs, then it is said that the storm made a direct hit on the coast.[56] As a result of the narrowness of this definition, the landfall area experiences half of a land-bound storm by the time the actual landfall occurs. For emergency preparedness, actions should be timed from when a certain wind speed or intensity of rainfall will reach land, not from when landfall will occur.[56]
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Quoting WeatherNerdPR:

You forgot about Bonnie already?


Did Bonnie make landfall as a TS? If so then I am wrong.
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Quoting BreadandCircuses:
Hermine is just what the doctor ordered, a relatively weak tropical system that will likely cause minimal damage and help alleviate drought conditions in parts of Texas. Its legacy will go down as being overall a beneficial system.

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the latest recon reading show that the center has moved due west since the last reading
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Quoting leo305:


when the center touches land, not the eye, the center of the eye
Landfall:
The intersection of the surface center of a tropical cyclone with a coastline. Because the strongest winds in a tropical cyclone are not located precisely at the center, it is possible for a cyclone's strongest winds to be experienced over land even if landfall does not occur. Similarly, it is possible for a tropical cyclone to make landfall and have its strongest winds remain over the water. Compare direct hit, indirect hit, and strike.
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>1. Introduction
Hurricane forecasters have long been puzzled by the apparent tendency of nascent
tropical cyclones to cease development or weaken as they traverse the eastern Caribbean
Sea. Given the low latitude of this region, most of these tropical disturbances are those
that develop from African easterly waves that are embedded in the deep, tropical
easterlies in the North Atlantic Ocean. Oftentimes, these surface atmospheric waves or
weak tropical cyclones and their associated convection unexpectedly decrease in intensity
in the eastern Caribbean, only to redevelop once they enter the western Caribbean, posing
a dilemma for forecasters.
An example of a tropical disturbance that weakened upon entering the eastern
Caribbean can be seen in Fig. 1a and Fig. 1b. Fig. 1a shows the disturbance at 0015Z on
July 16, 2004 with healthy convection just west of the Lesser Antilles. However, only
three hours later (Fig. 1b), the convection collapsed.
For years, the National Hurricane Center has colloquially referred to this eastern
Caribbean region as a hurricane graveyard. A good example of this was in the forecast
discussion for Tropical Depression Joyce in 2000, “…The outflow has improved and I
would dare to say that it is favorable for strengthening. However…Tropical Depression
Joyce is about to move into the area which the old timers call the hurricane graveyard.
Historically…with a few exceptions…tropical cyclones do not develop in this
area…Joyce is kept at 30 knots through 48 hours. Thereafter…some strengthening is
indicated when the depression reaches the western Caribbean…if it survives…” (Avila
2000).

---It should be interesting to see how Gaston interacts with the "hurricane graveyard" at peak season.
Action: Quote | Modify Comment
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Thanks DRM. And from the ther blog...








Quoting blsealevel:

im very conserned with this one, Rita put 9 ft of water in my house and it didnt even come within 200 miles of me.




Sorry to hear that about your house. She caused a pretty widespread swath of damage. I have been wondering with respect to Gaston why no one's expecting him to intensify in the Caribbean. I guess the DR answered because of the mountainous terrain he'll be crossing over. But even that isn't a given at this point. So he definitely has my attention.
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Quoting Cotillion:
Just to clarify:

Landfall is when the whole of the centre (or eye) moves over, or just the first bits of it?


when the center touches land, not the eye, the center of the eye
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Member Since: September 10, 2007 Posts: 0 Comments: 11425
"The storm is steadily organizing, and has a shot at reaching hurricane strength before the center moves ashore late tonight, near midnight."

Bingo. Hermine still has a good 4-6 hours over water if it continues to move generally towards the NNW at a slow rate.
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Afternoon folks,

If you want the full history of how Hermine developed, check out my synoptic history of Hermine on my blog

I am also forecasting Hermine to be between 65 to 80 mph winds at the center at landfall on that blog post. Find out the historical significance of Hermine if it does become a hurricane tonight, also on my blog.

Feel free to leave comments and enjoy!
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Quoting Levi32:
That chunk of dry air is still in the core, and Hermine has the appearance of needing to "wrap around" before the core can become solidified.

The dry air (seen on radar) seems to around 60% of the eye. What will happen if it goes completely around the center? Did see a slowdown/stationary for last 30 min, probably temporary.
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28.
Lol, SevereWeather. You beat me to it... but here's the graphic that goes with MCD#1791

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Station PTIT2 - 8779770 - Port Isabel, TX

Link

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Quoting AustinTXWeather:


Since we're in Central Texas, wondering how quickly hurricane 1/strong Tropical storm typically detensifies after it hits land - welcome insight. :)
Once it is over land it won't take long to weaken.
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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.