NHC Atlantic

Active tropical cyclones in the Atlantic, Caribbean, and the Gulf of Mexico

08/16/2017 10:41 AM
Hurricane Gert Graphics
Hurricane Gert 5-Day Uncertainty Track Image
5-Day Uncertainty Track last updated Wed, 16 Aug 2017 14:41:32 GMT

Hurricane Gert 34-Knot Wind Speed Probabilities
Wind Speed Probabilities last updated Wed, 16 Aug 2017 14:41:32 GMT

08/16/2017 10:36 AM
Hurricane Gert Forecast Discussion Number 15
Issued at 1100 AM AST Wed Aug 16 2017

000
WTNT43 KNHC 161436
TCDAT3

Hurricane Gert Discussion Number  15
NWS National Hurricane Center Miami FL       AL082017
1100 AM AST Wed Aug 16 2017

GOES-16 1-minute visible imagery has shown Gert's eye coming and
going over the past several hours, and for the first time a
distinct warm spot has appeared in infrared images.  However,
subjective Dvorak estimates are unchanged from six hours ago, and
the objective ADT has actually decreased a bit.  The initial
intensity is therefore held at 80 kt.  Gert has another 18-24 hours
before it reaches significantly colder waters north of the Gulf
Stream, so the cyclone still has the opportunity for a little more
strengthening later today and this evening.  Southwesterly shear is
expected to begin increasing tonight, and the higher shear and
colder water should cause a steady weakening trend to begin on
Thursday.  The global model fields indicate that Gert should be
fully extratropical, embedded in a frontal zone, within 48 hours,
and that is reflected in the official forecast.  There is still a
lot of uncertainty regarding when Gert will be absorbed by another
larger extratropical cyclone, but most of the guidance tends to
agree that it should be absorbed by day 5 over the north Atlantic.

Gert's forward speed continues to increase, and the hurricane is
now moving toward the northeast with a motion of 055/22 kt.  Gert
is embedded in mid-latitude westerly flow between a mid-level high
centered east of Bermuda and a large cut-off low over eastern
Canada, and this pattern should force the cyclone on a fast
northeastward pace over the north Atlantic at least for the next 72
hours.  A slower motion is forecast by day 4 once post-tropical
Gert interacts with the large cut-off low moving east of Atlantic
Canada.  There was very little change in the latest track guidance,
and no significant deviations from the previous NHC forecast were
required on this cycle.  The post-tropical portion of the track,
intensity, and wind radii forecasts incorporate guidance from NOAA's
Ocean Prediction Center.

Swells from Gert are affecting portions of the mid-Atlantic coast of
the United States, and are expected to spread northward to New
England and Atlantic Canada during the next day or two.  These
swells are likely to produce dangerous surf and rip current
conditions. Please consult products from your local weather forecast
office for more information.

FORECAST POSITIONS AND MAX WINDS

INIT  16/1500Z 37.4N  65.7W   80 KT  90 MPH
 12H  17/0000Z 39.0N  61.3W   85 KT 100 MPH
 24H  17/1200Z 41.8N  53.6W   75 KT  85 MPH
 36H  18/0000Z 45.5N  45.2W   65 KT  75 MPH
 48H  18/1200Z 49.5N  38.4W   50 KT  60 MPH...POST-TROP/EXTRATROP
 72H  19/1200Z 55.0N  32.2W   40 KT  45 MPH...POST-TROP/EXTRATROP
 96H  20/1200Z 55.0N  26.0W   40 KT  45 MPH...POST-TROP/EXTRATROP
120H  21/1200Z...ABSORBED BY A LARGER EXTRATROPICAL LOW

$$
Forecaster Berg


08/16/2017 10:36 AM
Hurricane Gert Wind Speed Probabilities Number 15
Issued at 1500 UTC WED AUG 16 2017

000
FONT13 KNHC 161436
PWSAT3
                                                                    
HURRICANE GERT WIND SPEED PROBABILITIES NUMBER  15                  
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL082017               
1500 UTC WED AUG 16 2017                                            
                                                                    
AT 1500Z THE CENTER OF HURRICANE GERT WAS LOCATED NEAR LATITUDE 37.4
NORTH...LONGITUDE 65.7 WEST WITH MAXIMUM SUSTAINED WINDS NEAR 80 KTS
...90 MPH...150 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           
        12Z WED 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 34...50...64 KT SHOWN WHEN THE 5-DAY              
64-KT CUMULATIVE PROBABILITY IS AT LEAST 1 PERCENT.                 
                                                                    
                                                                    
  - - - - WIND SPEED PROBABILITIES FOR SELECTED LOCATIONS - - - -   
                                                                    
               FROM    FROM    FROM    FROM    FROM    FROM    FROM 
  TIME       12Z WED 00Z THU 12Z THU 00Z FRI 12Z FRI 12Z SAT 12Z SUN
PERIODS         TO      TO      TO      TO      TO      TO      TO  
             00Z THU 12Z THU 00Z FRI 12Z FRI 12Z SAT 12Z SUN 12Z MON
                                                                    
FORECAST HOUR    (12)   (24)    (36)    (48)    (72)    (96)   (120)
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 
LOCATION       KT                                                   
                                                                    
HIBERNIA OILFD 34  X   X( X)   7( 7)   1( 8)   X( 8)   X( 8)   X( 8)
 
CAPE RACE NFLD 34  X   1( 1)   2( 3)   X( 3)   X( 3)   X( 3)   X( 3)
 
$$                                                                  
FORECASTER BERG                                                     

08/16/2017 10:36 AM
Hurricane Gert Public Advisory Number 15
Issued at 1100 AM AST Wed Aug 16 2017

000
WTNT33 KNHC 161436
TCPAT3

BULLETIN
Hurricane Gert Advisory Number  15
NWS National Hurricane Center Miami FL       AL082017
1100 AM AST Wed Aug 16 2017

...GERT ACCELERATING NORTHEASTWARD OVER THE NORTHWESTERN ATLANTIC...


SUMMARY OF 1100 AM AST...1500 UTC...INFORMATION
-----------------------------------------------
LOCATION...37.4N 65.7W
ABOUT 355 MI...575 KM N OF BERMUDA
ABOUT 510 MI...820 KM SSW OF HALIFAX NOVA SCOTIA
MAXIMUM SUSTAINED WINDS...90 MPH...150 KM/H
PRESENT MOVEMENT...NE OR 55 DEGREES AT 25 MPH...41 KM/H
MINIMUM CENTRAL PRESSURE...975 MB...28.80 INCHES


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


DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
At 1100 AM AST (1500 UTC), the center of Hurricane Gert was located
near latitude 37.4 North, longitude 65.7 West.  Gert is accelerating
toward the northeast near 25 mph (41 km/h).  An even faster motion
toward the northeast or east-northeast is expected through early
Friday.

Maximum sustained winds are near 90 mph (150 km/h) with higher
gusts.  Some strengthening is possible later today or tonight, but
Gert is likely to begin weakening on Thursday.  Gert should become
an extratropical low by Thursday night.

Hurricane-force winds extend outward up to 35 miles (55 km) from the
center, and tropical-storm-force winds extend outward up to 125
miles (205 km).

The estimated minimum central pressure is 975 mb (28.80 inches).


HAZARDS AFFECTING LAND
----------------------
SURF:  Swells generated by Gert will spread northward along the
east coast of the United States from Virginia northward to
New England and Atlantic Canada during the next day or two.
Swells are also expected to continue to affect Bermuda through
tonight.  These swells are likely to cause life-threatening surf and
rip current conditions.  Please consult products from your local
weather forecast office.


NEXT ADVISORY
-------------
Next complete advisory at 500 PM AST.

$$
Forecaster Berg


08/16/2017 10:36 AM
Summary for Hurricane Gert (AT3/AL082017)
...GERT ACCELERATING NORTHEASTWARD OVER THE NORTHWESTERN ATLANTIC... As of 11:00 AM AST Wed Aug 16 the center of Gert was located near 37.4, -65.7 with movement NE at 25 mph. The minimum central pressure was 975 mb with maximum sustained winds of about 90 mph.

08/16/2017 10:35 AM
Hurricane Gert Forecast Advisory Number 15
Issued at 1500 UTC WED AUG 16 2017

000
WTNT23 KNHC 161435
TCMAT3

HURRICANE GERT FORECAST/ADVISORY NUMBER  15
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL082017
1500 UTC WED AUG 16 2017

THERE ARE NO COASTAL WATCHES OR WARNINGS IN EFFECT.

HURRICANE CENTER LOCATED NEAR 37.4N  65.7W AT 16/1500Z
POSITION ACCURATE WITHIN  20 NM

PRESENT MOVEMENT TOWARD THE NORTHEAST OR  55 DEGREES AT  22 KT

ESTIMATED MINIMUM CENTRAL PRESSURE  975 MB
MAX SUSTAINED WINDS  80 KT WITH GUSTS TO 100 KT.
64 KT....... 30NE  30SE   0SW   0NW.
50 KT....... 50NE  50SE   0SW   0NW.
34 KT....... 90NE 110SE  70SW  40NW.
12 FT SEAS..120NE 210SE 180SW 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 37.4N  65.7W AT 16/1500Z
AT 16/1200Z CENTER WAS LOCATED NEAR 36.8N  67.1W

FORECAST VALID 17/0000Z 39.0N  61.3W
MAX WIND  85 KT...GUSTS 105 KT.
64 KT... 30NE  35SE  15SW   0NW.
50 KT... 50NE  60SE  30SW  20NW.
34 KT... 90NE 130SE  90SW  50NW.

FORECAST VALID 17/1200Z 41.8N  53.6W
MAX WIND  75 KT...GUSTS  90 KT.
64 KT... 30NE  40SE  20SW   0NW.
50 KT... 50NE  70SE  40SW   0NW.
34 KT... 90NE 150SE 120SW  50NW.

FORECAST VALID 18/0000Z 45.5N  45.2W
MAX WIND  65 KT...GUSTS  80 KT.
64 KT...  0NE  40SE  30SW   0NW.
50 KT... 50NE  70SE  50SW   0NW.
34 KT...100NE 150SE 120SW  50NW.

FORECAST VALID 18/1200Z 49.5N  38.4W...POST-TROP/EXTRATROP
MAX WIND  50 KT...GUSTS  60 KT.
50 KT... 60NE  90SE   0SW   0NW.
34 KT...120NE 150SE 120SW  60NW.

FORECAST VALID 19/1200Z 55.0N  32.2W...POST-TROP/EXTRATROP
MAX WIND  40 KT...GUSTS  50 KT.
34 KT...150NE 180SE 120SW 120NW.

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 20/1200Z 55.0N  26.0W...POST-TROP/EXTRATROP
MAX WIND  40 KT...GUSTS  50 KT.

OUTLOOK VALID 21/1200Z...ABSORBED BY A LARGER EXTRATROPICAL LOW

REQUEST FOR 3 HOURLY SHIP REPORTS WITHIN 300 MILES OF 37.4N  65.7W

NEXT ADVISORY AT 16/2100Z

$$
FORECASTER BERG



08/16/2017 07:48 AM
Atlantic Tropical Weather Outlook

000
ABNT20 KNHC 161147
TWOAT

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
800 AM EDT Wed Aug 16 2017

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

The National Hurricane Center is issuing advisories on Hurricane
Gert, located a few hundred miles northwest of Bermuda.

A low pressure system located about 900 miles east of the Lesser
Antilles continues to produce disorganized showers and a few
thunderstorms. This system is moving westward at 15 to 20 mph,
and it is expected to cross into the Caribbean Sea on Friday.
Upper-level winds are forecast to become a little more conducive
for development during the next several days, and interests in the
Lesser Antilles should monitor the progress of this system.
* Formation chance through 48 hours...low...30 percent.
* Formation chance through 5 days...medium...40 percent.

A second area of low pressure located several hundred miles west of
the Cabo Verde Islands is also producing disorganized showers and
thunderstorms. Gradual development of this system is possible
during the next few days before upper-level winds become less
conducive over the weekend. This system is expected to move
west-northwestward at 15 to 20 mph during the next several days.
* Formation chance through 48 hours...low...30 percent.
* Formation chance through 5 days...medium...40 percent.

A tropical wave near the west coast of Africa is producing a
large area of disorganized showers and thunderstorms.
Environmental conditions appear conducive for gradual development of
this wave while it moves westward to west-northwestward at about 15
mph during the next several days.
* Formation chance through 48 hours...low...near 0 percent.
* Formation chance through 5 days...medium...40 percent.

$$
Forecaster Berg