National Hurricane Center (Atlantic)

Atlantic Tropical Weather Outlook


000
ABNT20 KNHC 262337
TWOAT

TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
800 PM EDT FRI AUG 26 2016

For the North Atlantic...Caribbean Sea and the Gulf of Mexico:

The National Hurricane Center is issuing advisories on Tropical
Storm Gaston, located about 1000 miles east-southeast of Bermuda.

Shower activity associated with a weak area of low pressure located
in the central Bahamas has increased during the past several hours
but it remains disorganized. Upper-level winds are not favorable
for significant development during the next day or so while the
system moves west-northwestward at about 10 mph. Environmental
conditions could become a little more conducive for some development
when the system reaches the eastern Gulf of Mexico early next week.

Heavy rains, with the potential to cause flash floods and mud
slides, are likely to continue over Hispaniola tonight and Saturday.
This activity is expected to spread over eastern and central Cuba
through the weekend. Gusty winds and locally heavy rainfall are
likely over portions of the Bahamas, and will spread into parts of
southern Florida and the Florida Keys over the weekend. Interests
elsewhere in Florida and the eastern Gulf of Mexico should continue
to monitor the progress of this disturbance.
* Formation chance through 48 hours...low...20 percent
* Formation chance through 5 days...medium...50 percent

Disorganized shower and thunderstorm activity located over the
north-central Gulf of Mexico is associated with a weak trough of
low pressure. Conditions are not expected to be favorable for
development before it reaches the coast of Texas over the weekend.
This disturbance could produce heavy rainfall along the Gulf Coast
from Louisiana to southeastern Texas during the next couple of days.
For additional information, please see products from your local
National Weather Service office.
* Formation chance through 48 hours...low...10 percent
* Formation chance through 5 days...low...10 percent

An area of disturbed weather, associated with a broad area of low
pressure, has formed a couple of hundred miles south of Bermuda.
Little motion is anticipated during the next two days, and a
slow westward heading should begin thereafter. Development of
this system, if any, is likely to be slow to occur due to this
system's proximity to dry air.
* Formation chance through 48 hours...low...10 percent
* Formation chance through 5 days...low...20 percent

$$
Forecaster Avila

Tropical Storm GASTON Graphics

Tropical Storm GASTON 5-Day Uncertainty Track Image
5-Day Uncertainty Track last updated Fri, 26 Aug 2016 20:32:10 GMT

Tropical Storm GASTON 34-Knot Wind Speed Probabilities
Wind Speed Probabilities last updated Fri, 26 Aug 2016 21:06:40 GMT

Tropical Storm GASTON Forecast Discussion Number 17

Issued at 500 PM AST FRI AUG 26 2016

000
WTNT42 KNHC 262032
TCDAT2

TROPICAL STORM GASTON DISCUSSION NUMBER  17
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL072016
500 PM AST FRI AUG 26 2016

The hostile vertical shear from an upper low to Gaston's southwest
appears to be dropping with the SHIPS and CIMSS shear analyses down
to about 15 kt.  The deep convection, however, is still mainly
north
of the center and lacks significant banding features.  SAB and TAFB
Dvorak current intensity estimates range from 45 to 55 kt, down
slightly from earlier today.  In deference to the 1330Z ASCAT
scatterometer pass and the very robust low-level circulation
evident
in the visible imagery during the day, the maximum winds are kept
at
55 kt.

As Gaston moves away from the upper-level low, the shear should
continue to drop to values between 5 and 10 kt by tomorrow.  The
shear should then stay low through about 72 h while the cyclone
traverses over quite warm waters.  A key uncertainty in the
intensity forecast is from the environmental low-level moisture,
which may decrease substantially during the next few days.  This
could reduce the otherwise quite conducive conditions that Gaston
should soon experience. After about three days, Gaston is likely to
encounter strong mid-latitude upper-level westerlies and a return
of
hostile shear while SSTs steadily drop. The official NHC forecast
is
for steady intensification between days one and three, with gradual
weakening thereafter.  This forecast is based upon a blend of the
tightly packed HWRF/COAMPS/SHIPS/LGEM models and is the same as in
the previous advisory.

Gaston's center is just tucked in on the southern edge of the deep
convection, allowing for a confident assessment of the initial
position. The tropical storm is moving toward the northwest at a
15-kt clip, as it is being steered between the strong upper low and
a subtropical ridge to its northeast.  Around 72 h, Gaston should
slow to a crawl as it reaches a weak steering pattern.  But by the
end of the forecast period, the system should be accelerating
northeastward as it enters the mid-latitude westerlies.  The track
forecast is based upon a blend of the GFS and ECMWF global models
and is nearly the same from that in the previous advisory.

The initial 34- and 50-kt wind radii were only slightly tweaked
based upon the ASCAT scatterometer pass and the wind radii forecast
is similar to the RVCN consensus technique.


FORECAST POSITIONS AND MAX WINDS

INIT  26/2100Z 26.2N  49.7W   55 KT  65 MPH
 12H  27/0600Z 27.4N  51.5W   55 KT  65 MPH
 24H  27/1800Z 28.6N  53.5W   65 KT  75 MPH
 36H  28/0600Z 29.7N  54.8W   75 KT  85 MPH
 48H  28/1800Z 30.4N  55.8W   85 KT 100 MPH
 72H  29/1800Z 31.5N  56.0W   95 KT 110 MPH
 96H  30/1800Z 32.5N  53.5W   90 KT 105 MPH
120H  31/1800Z 34.5N  49.0W   80 KT  90 MPH

$$
Forecaster Landsea


Tropical Storm GASTON Wind Speed Probabilities Number 17

Issued at 2100 UTC FRI AUG 26 2016

000
FONT12 KNHC 262031
PWSAT2
                                                                   

TROPICAL STORM GASTON WIND SPEED PROBABILITIES NUMBER  17          

NWS NATIONAL HURRICANE CENTER MIAMI FL       AL072016              

2100 UTC FRI AUG 26 2016                                           

                                                                   

AT 2100Z THE CENTER OF TROPICAL STORM GASTON WAS LOCATED NEAR      

LATITUDE 26.2 NORTH...LONGITUDE 49.7 WEST WITH MAXIMUM SUSTAINED   

WINDS NEAR 55 KTS...65 MPH...100 KM/H.                             

                                                                   

Z INDICATES COORDINATED UNIVERSAL TIME (GREENWICH)                 

   ATLANTIC STANDARD TIME (AST)...SUBTRACT 4 HOURS FROM Z TIME     

   EASTERN  DAYLIGHT TIME (EDT)...SUBTRACT 4 HOURS FROM Z TIME     

   CENTRAL  DAYLIGHT TIME (CDT)...SUBTRACT 5 HOURS FROM Z TIME     

                                                                   

WIND SPEED PROBABILITY TABLE FOR SPECIFIC LOCATIONS                

                                                                   

CHANCES OF SUSTAINED (1-MINUTE AVERAGE) WIND SPEEDS OF AT LEAST    

   ...34 KT (39 MPH... 63 KM/H)...                                 

   ...50 KT (58 MPH... 93 KM/H)...                                 

   ...64 KT (74 MPH...119 KM/H)...                                 

FOR LOCATIONS AND TIME PERIODS DURING THE NEXT 5 DAYS              

                                                                   

PROBABILITIES FOR LOCATIONS ARE GIVEN AS OP(CP) WHERE              

    OP  IS THE PROBABILITY OF THE EVENT BEGINNING DURING           

        AN INDIVIDUAL TIME PERIOD (ONSET PROBABILITY)              

   (CP) IS THE PROBABILITY OF THE EVENT OCCURRING BETWEEN          

        18Z FRI AND THE FORECAST HOUR (CUMULATIVE PROBABILITY)     

                                                                   

PROBABILITIES ARE GIVEN IN PERCENT                                 

X INDICATES PROBABILITIES LESS THAN 1 PERCENT                      

PROBABILITIES FOR 34 KT AND 50 KT ARE SHOWN AT A GIVEN LOCATION
WHEN
THE 5-DAY CUMULATIVE PROBABILITY IS AT LEAST 3 PERCENT.            

PROBABILITIES FOR 64 KT ARE SHOWN WHEN THE 5-DAY CUMULATIVE        

PROBABILITY IS AT LEAST 1 PERCENT.                                 

                                                                   

                                                                   

  - - - - WIND SPEED PROBABILITIES FOR SELECTED LOCATIONS - - - -  

                                                                   

               FROM    FROM    FROM    FROM    FROM    FROM    FROM

  TIME       18Z FRI 06Z SAT 18Z SAT 06Z SUN 18Z SUN 18Z MON 18Z
TUE
PERIODS         TO      TO      TO      TO      TO      TO      TO 

             06Z SAT 18Z SAT 06Z SUN 18Z SUN 18Z MON 18Z TUE 18Z
WED
                                                                   

FORECAST HOUR    (12)   (24)    (36)    (48)    (72)    (96)  
(120)
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

LOCATION       KT                                                  

                                                                   

$$                                                                 

FORECASTER LANDSEA                                                 


Summary for Tropical Storm GASTON (AT2/AL072016)

...GASTON FORECAST TO REGAIN HURRICANE INTENSITY... As of 5:00 PM AST Fri Aug 26 the center of GASTON was located near 26.2, -49.7 with movement NW at 17 mph. The minimum central pressure was 997 mb with maximum sustained winds of about 65 mph.

Tropical Storm GASTON Public Advisory Number 17

Issued at 500 PM AST FRI AUG 26 2016

000
WTNT32 KNHC 262031
TCPAT2

BULLETIN
TROPICAL STORM GASTON ADVISORY NUMBER  17
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL072016
500 PM AST FRI AUG 26 2016

...GASTON FORECAST TO REGAIN HURRICANE INTENSITY...


SUMMARY OF 500 PM AST...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...26.2N 49.7W
ABOUT 1000 MI...1610 KM ESE OF BERMUDA
ABOUT 1020 MI...1640 KM NE OF THE NORTHERN LEEWARD ISLANDS
MAXIMUM SUSTAINED WINDS...65 MPH...100 KM/H
PRESENT MOVEMENT...NW OR 320 DEGREES AT 17 MPH...28 KM/H
MINIMUM CENTRAL PRESSURE...997 MB...29.44 INCHES


WATCHES AND WARNINGS
--------------------
There are no coastal watches or warnings in effect.


DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
At 500 PM AST (2100 UTC), the center of Tropical Storm Gaston was
located near latitude 26.2 North, longitude 49.7 West. Gaston is
moving toward the northwest near 17 mph (28 km/h) and the system
should continue in this general direction at a slower rate of
forward speed during the next two days.

Maximum sustained winds are near 65 mph (100 km/h) with higher
gusts.  Some strengthening is forecast during the next 48 hours.
Gaston is expected to regain hurricane intensity on Saturday.

Tropical-storm-force winds extend outward up to 150 miles (240 km)
from the center.

The estimated minimum central pressure is 997 mb (29.44 inches).


HAZARDS AFFECTING LAND
----------------------
None.


NEXT ADVISORY
-------------
Next complete advisory at 1100 PM AST.

$$
Forecaster Landsea


Tropical Storm GASTON Forecast Advisory Number 17

Issued at 2100 UTC FRI AUG 26 2016

000
WTNT22 KNHC 262030
TCMAT2
 
TROPICAL STORM GASTON FORECAST/ADVISORY NUMBER  17
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL072016
2100 UTC FRI AUG 26 2016
 
THERE ARE NO COASTAL WATCHES OR WARNINGS IN EFFECT.
 
TROPICAL STORM CENTER LOCATED NEAR 26.2N  49.7W AT 26/2100Z
POSITION ACCURATE WITHIN  15 NM
 
PRESENT MOVEMENT TOWARD THE NORTHWEST OR 320 DEGREES AT  15 KT
 
ESTIMATED MINIMUM CENTRAL PRESSURE  997 MB
MAX SUSTAINED WINDS  55 KT WITH GUSTS TO  65 KT.
50 KT....... 50NE  30SE   0SW  30NW.
34 KT.......130NE  80SE  40SW 100NW.
12 FT SEAS..150NE 120SE  90SW 120NW.
WINDS AND SEAS VARY GREATLY IN EACH QUADRANT.  RADII IN NAUTICAL
MILES ARE THE LARGEST RADII EXPECTED ANYWHERE IN THAT QUADRANT.
 
REPEAT...CENTER LOCATED NEAR 26.2N  49.7W AT 26/2100Z
AT 26/1800Z CENTER WAS LOCATED NEAR 25.8N  49.1W
 
FORECAST VALID 27/0600Z 27.4N  51.5W
MAX WIND  55 KT...GUSTS  65 KT.
50 KT... 50NE  30SE   0SW  30NW.
34 KT...130NE  80SE  40SW 100NW.
 
FORECAST VALID 27/1800Z 28.6N  53.5W
MAX WIND  65 KT...GUSTS  80 KT.
64 KT... 30NE   0SE   0SW   0NW.
50 KT... 70NE  40SE  30SW  40NW.
34 KT...130NE 100SE  60SW 100NW.
 
FORECAST VALID 28/0600Z 29.7N  54.8W
MAX WIND  75 KT...GUSTS  90 KT.
64 KT... 30NE  20SE   0SW  20NW.
50 KT... 70NE  40SE  30SW  40NW.
34 KT...130NE 100SE  80SW 100NW.
 
FORECAST VALID 28/1800Z 30.4N  55.8W
MAX WIND  85 KT...GUSTS 105 KT.
50 KT... 70NE  50SE  40SW  50NW.
34 KT...130NE 100SE  80SW 100NW.
 
FORECAST VALID 29/1800Z 31.5N  56.0W
MAX WIND  95 KT...GUSTS 115 KT.
50 KT... 70NE  70SE  60SW  60NW.
34 KT...130NE 130SE 100SW 100NW.
 
EXTENDED OUTLOOK. NOTE...ERRORS FOR TRACK HAVE AVERAGED NEAR 150 NM
ON DAY 4 AND 200 NM ON DAY 5...AND FOR INTENSITY NEAR 15 KT EACH
DAY
 
OUTLOOK VALID 30/1800Z 32.5N  53.5W
MAX WIND  90 KT...GUSTS 110 KT.
 
OUTLOOK VALID 31/1800Z 34.5N  49.0W
MAX WIND  80 KT...GUSTS 100 KT.
 
REQUEST FOR 3 HOURLY SHIP REPORTS WITHIN 300 MILES OF 26.2N  49.7W
 
NEXT ADVISORY AT 27/0300Z
 
$$
FORECASTER LANDSEA
 
 

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