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TD Dolly


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000

WTNT45 KNHC 012036

TCDAT5

TROPICAL DEPRESSION FIVE DISCUSSION NUMBER 1

NWS NATIONAL HURRICANE CENTER MIAMI FL AL052014

400 PM CDT MON SEP 01 2014

An Air Force Reserve Unit reconnaissance aircraft investigating the

low pressure area over the southwest Gulf of Mexico found a

well-defined center of circulation. The system has a curved band of

deep convection that wraps around the southern and eastern portions

of the circulation. Thus the system is being designated as a

tropical depression at this time. The maximum winds reported by the

aircraft so far support an intensity of 25 kt. Although the

cyclone is situated over very warm waters of near 30 deg C, the

atmospheric environment is not ideal for strengthening. Dynamical

models indicate that significant northerly to northwesterly

vertical shear should affect the tropical cyclone for the next 36

hours and this is likely to limit intensification up to landfall.

After landfall, dissipation should be quick due to the mountainous

terrain of Mexico. The official wind speed forecast is a little

above the intensity model consensus.

The initial motion is west-northwestward or around 295/11. The

steering scenario appears to be fairly straightforward. The flow

to the south of a mid-level ridge along the northern Gulf of Mexico

coast should maintain a west-northwestward track for the next 36

hours, i.e. through the expected time of landfall. The official

track forecast is very close to the latest dynamical model

consensus.

FORECAST POSITIONS AND MAX WINDS

INIT 01/2100Z 20.1N 93.6W 25 KT 30 MPH

12H 02/0600Z 21.1N 94.8W 30 KT 35 MPH

24H 02/1800Z 21.9N 96.3W 35 KT 40 MPH

36H 03/0600Z 22.4N 97.9W 40 KT 45 MPH...INLAND

48H 03/1800Z...DISSIPATED INLAND

$

Forecaster Pasch

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I'm thinking we could see a center relocation more north.  The center the NHC is tracking is very weak.  I'm thinking a LLC is forming more toward 21.5N and 93W.  

I second this; when recon investigated both areas, the southwest one (the one NHC used in the 21z advisory) was better defined. However, based on visible satellite loops, the northeast one seems to be becoming dominant. If that were the case, the ultimate landfall location would shift farther north, and this would have slightly more time to organize.

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Looks like the NHC adjusted the center practically due north.  Still not north enough in my opinion.  Movement is now NW, which it looks like it could continue NW before bending back west as the ridge builds in.  This looks like it's going to be more on the northern end of the forecast guidance.   

 

SUMMARY OF 700 PM CDT...0000 UTC...INFORMATION
----------------------------------------------
LOCATION...20.5N 93.7W
ABOUT 240 MI...390 KM E OF TUXPAN MEXICO
MAXIMUM SUSTAINED WINDS...30 MPH...45 KM/H
PRESENT MOVEMENT...NW OR 305 DEGREES AT 12 MPH...19 KM/H
MINIMUM CENTRAL PRESSURE...1008 MB...29.77 INCHES
 
It was 20.1N 93.6W last advisory.  
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rgb_lalo-animated.gif

 

TROPICAL STORM DOLLY DISCUSSION NUMBER   3
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL052014
400 AM CDT TUE SEP 02 2014

An Air Force Reserve reconnaissance aircraft investigating the
cyclone early this morning found 925 mb flight-level winds of 50-53
kt in the northeast quadrant and adjusted SFMR winds of at least 40
kt.  In addition, two ASCAT overpasses at 0313 UTC and 0406 UTC
indicated surface winds of 40-41 kt in the eastern quadrant. Based
on these wind data, the intensity has been increased to 40 kt,
making the cyclone the fourth tropical storm of the 2014 Atlantic
hurricane season. These wind data also required the initial
position to be relocated about 60 nmi north of the previous track.

The initial motion estimate is northwestward or 305/12 kt, which is
based on a blend of passive microwave, scatterometer, and
conventional satellite fix data. Other than the northward relocation
of the center position, the forecast track reasoning remains
unchanged from the previous advisories. The tropical storm is
expected to gradually turn more toward the west-northwest as Dolly
skirts along the southern periphery of a strong mid-level ridge that
is located across most of the Gulf of Mexico and the southeastern
United States. Landfall along the northeastern coast of Mexico is
expected in about 24 hours, followed by dissipation in 48 hours
over the rugged terrain of the Sierra Madre Oriental mountains. The
NHC forecast track is similar to the consensus model TVCA, and lies
roughly in the middle of the guidance envelope.

About 20 kt of north-northwesterly vertical shear is affecting
Dolly, which has resulted in most of the convection being displaced
well to the south and east of the exposed low-level circulation.
However, new convection has recently developed near and just to the
southeast of the center, and with the shear forecast to decrease to
about 15 kt during the next 12 hours, some additional slight
strengthening is possible before Dolly makes landfall.

The surface wind data from the reconnaissance aircraft and the
two scatterometer passes indicate that the tropical-storm-force wind
field has expanded significantly in the eastern semicircle. Since
the pressure gradient between Dolly and the large high over the
Gulf of Mexico is expected to remain quite strong for the next 36
hours or so, the Government of Mexico has extended the tropical
storm warning area northward to Barra El Mezquital. However, no
additional northward extension of the warning area appears likely
at this time.

The primary threat from this system is expected to be heavy
rainfall, which is likely to cause flash flooding and mud slides
over portions of eastern Mexico.

FORECAST POSITIONS AND MAX WINDS

INIT  02/0900Z 22.6N  94.8W   40 KT  45 MPH
12H  02/1800Z 23.1N  95.9W   45 KT  50 MPH
24H  03/0600Z 23.7N  97.5W   45 KT  50 MPH
36H  03/1800Z 24.1N  98.9W   35 KT  40 MPH...INLAND
48H  04/0600Z...DISSIPATED INLAND

$$
Forecaster Stewart

 

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It's about 6-8 hours from landfall. I expect no significant changes intensity wise, shear just didn't subsided enough...maybe it's 50kts now, would have to wait for recon. It also turned more to the W, it's been heading 290 degrees for the last 3 hours or so..maybe even more west the last hour, but that's not a significant time window.

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Recon may have missed the center...

 

Looks exposed and racing west, as you stated. 

 

It's not racing west...it's mostly exposed but going after the deep convection south (it's moving around 200-210)...it has lost half a degree in the last 1.5 hours.

 

Maybe a new center is forming near the deep convection? Low level vorticity would backup this idea

post-29-0-15408400-1409679166_thumb.gif

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Yes, saw that one, but recon confirmed a closed circulation around that time (that's from late evening yesterday our time)

 

Ah my bad, here's the new one.  Definitely a closed circulation.  You can see with the NW-SE elongated center where the old one is beginning to die and a new one is trying to form, but looks especially awkward during the transition stage. 

 

post-378-0-73935100-1409681519_thumb.png

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Ah my bad, here's the new one.  Definitely a closed circulation.  You can see with the NW-SE elongated center where the old one is beginning to die and a new one is trying to form, but looks especially awkward during the transition stage. 

 

attachicon.gifWMBds63.png

Yeah, kinda of 8 shaped.

 

Anyhoo, it's official now, reformed to the south 22N 96.5W

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It looks to me this thing will come ashore near Tampico with the re-location. I am not sure why NHC didn't adjust the track accordingly.

They don't do track adjustments for the intermediate advisories...they simply adjust the initialization point, but keep the forecasted track.

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Meso vorts are rotating all around the elongated 'center'. With the large wind field, it probably doesn't make any difference at this point. This mess will be inland in a few hours and dump copious rainfall amounts from Coatzacoalcos to just S of La Pesca.

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