Fromt eh NHC
BULLETIN
Potential Tropical Cyclone Two Advisory Number 3
NWS National Hurricane Center Miami FL AL022019
1000 PM CDT Wed Jul 10 2019
…SYSTEM IS ALMOST A TROPICAL DEPRESSION…
…STORM SURGE, HEAVY RAINS, AND HURRICANE CONDITIONS ARE
POSSIBLE ACROSS THE NORTH-CENTRAL GULF COAST IN A COUPLE OF DAYS…
SUMMARY OF 1000 PM CDT…0300 UTC…INFORMATION
———————————————–
LOCATION…27.7N 88.0W
ABOUT 120 MI…190 KM SE OF THE MOUTH OF THE MISSISSIPPI RIVER
ABOUT 240 MI…385 KM SE OF MORGAN CITY LOUISIANA
MAXIMUM SUSTAINED WINDS…30 MPH…45 KM/H
PRESENT MOVEMENT…WSW OR 245 DEGREES AT 9 MPH…15 KM/H
MINIMUM CENTRAL PRESSURE…1009 MB…29.80 INCHES
WATCHES AND WARNINGS
——————–
CHANGES WITH THIS ADVISORY…
None.
SUMMARY OF WATCHES AND WARNINGS IN EFFECT…
A Storm Surge Watch is in effect for…
* Mouth of the Pearl River to Intracoastal City
A Hurricane Watch is in effect for…
* Mouth of the Mississippi River to Cameron
A Tropical Storm Watch is in effect for…
* Mouth of the Mississippi River northward to the Mouth of the Pearl
River
A Storm Surge Watch means there is a possibility of life-
threatening inundation from rising water moving inland from the
coastline in the indicated locations during the next 48 hours.
For a depiction of areas at risk please see the National Weather
Service Storm Surge Watch/Warning Graphic available at
hurricanes.gov.
A Hurricane Watch means that hurricane conditions are possible
within the watch area. A watch is typically issued 48 hours
before the anticipated first occurrence of tropical-storm-force
winds conditions that make outside preparations difficult or
dangerous.
A Tropical Storm Watch means that tropical storm conditions are
possible within the watch area generally within 48 hours.
Interests elsewhere along the U.S. Gulf Coast from the Upper Texas
Coast to the Florida Panhandle should monitor the progress of this
system.
For storm information specific to your area, including possible
inland watches and warnings, please monitor products issued by your
local National Weather Service forecast office.
DISCUSSION AND OUTLOOK
———————-
At 1000 PM CDT (0300 UTC), the disturbance was centered near
latitude 27.7 North, longitude 88.0 West. The system is moving
toward the west-southwest near 9 mph (15 km/h). A motion toward the
west is expected on Thursday, followed by a west-northwest motion on
Friday and a northwestward motion by early Saturday. On the forecast
track, the system is expected to approach the Louisiana coast this
weekend.
Maximum sustained winds remain near 30 mph (45 km/h) with higher
gusts. Strengthening is forecast during the next couple of days, and
the disturbance is forecast to become a tropical depression early
Thursday, a tropical storm by late Thursday, and a hurricane by late
Friday.
The circulation of the low continues to become better defined, and
the system is expected to become a tropical depression on Thursday.
*Formation chance through 48 hours…high…near 100 percent
*Formation chance through 5 days…high…near 100 percent
The estimated minimum central pressure based on data from the NOAA
Hurricane Hunters and surface observations is 1009 mb (29.80
inches).
HAZARDS AFFECTING LAND
———————-
Key Messages for this system can be found in the Tropical Cyclone
Discussion under AWIPS header MIATCDAT2 and WMO header WTNT32 KNHC.
STORM SURGE: The combination of a dangerous storm surge and the
tide will cause normally dry areas near the coast to be flooded by
rising waters moving inland from the shoreline. The water could
reach the following heights above ground somewhere in the indicated
areas if the peak surge occurs at the time of high tide…
Mouth of the Pearl River to Intracoastal City…3 to 6 ft
Surge-related flooding depends on the relative timing of the surge
and the tidal cycle, and can vary greatly over short distances. For
information specific to your area, please see products issued by
your local National Weather Service forecast office.
RAINFALL: The system is expected to produce total additional rain
accumulations of 10 to 15 inches near and inland of the central Gulf
Coast through early next week, with isolated maximum rainfall
amounts of 20 inches.
Rainfall amounts exceeding 6 to 9 inches have already occurred
across portions of the New Orleans metropolitan area today, which
has resulted in flooding.
WIND: Hurricane conditions are possible within the Hurricane Watch
area by Friday night, with tropical storm conditions possible by
early Friday.
NEXT ADVISORY
————-
Next intermediate advisory at 100 AM CDT.
Next complete advisory at 400 AM CDT.
Data from An Air Force Reserve reconnaissance aircraft, surface
observations, and satellite imagery indicate that the broad low
pressure system located over the northeastern Gulf of Mexico still
lacks a well-defined circulation center. Multiple low-level swirls
associated with individual convective cells were noted in the
aircraft wind data. However, shower and thunderstorm activity has
been increasing over the past couple of hours in the previously
convective-free northern semicircle, an indication that low-level
wind field is beginning to improve in that region of the cyclone.
Upper-level outflow has become well established except to the north
where modest northerly wind shear is inhibiting the outflow. The
initial intensity of 25 kt is based on earlier scatterometer wind
data and recent recon winds of 25-30 kt to the south and west of the
center.
The initial motion estimate remains 245/07 kt. The latest model
guidance continues in good agreement on the cyclone moving generally
toward the west-southwest or southwest for the next 24 hours or so,
followed by a westward motion on Friday. Afterwards, however, the
model guidance diverges significantly. The 12Z ECMWF, GFS, HWRF,
and HMON models have shifted farther east and turn the cyclone
northwestward to northward in 48-72 hours, moving it inland along
the south-central and southeastern coasts of Louisiana. In contrast,
the UKMET has shifted farther west and keeps the system on more of
westward track, taking it inland along the central Texas coast. The
main difference is how the models handle the ridge to the north,
with the ECMWF, GFS, HWRF, and HMON rapidly eroding the ridge as a
weak shortwave trough passes to the north of the cyclone, whereas
the UKMET shows the ridge not weakening as much due to the
shortwave trough weakening as it lifts out to the east, which
allows the ridge to remain intact. Due to this significant
bifurcation in NHC’s most reliable track model guidance, the best
course of action is to slow down the forward speed and only make
minor adjustments to the overall tack, which has been shifted
slightly to the east, but not as far east as the simple consensus
and HCCA models.
Only slow strengthening is forecast for the next 24-36 hours due to
the lack of a well-defined center and inner-core wind field, along
with some modest northerly wind shear. By 48 hours and beyond,
however, the combination of very low vertical wind shear, an
impressive outflow pattern forecast by all of the global and
regional models, and anomalously warm sea-surface temperatures of
30-31C should allow for significant intensification to hurricane
strength before landfall occurs after 72 hours. Given that the
system is still in the formative stages, the official intensity
forecast remains a little below IVCN consensus through 48
hours and trends higher toward the ECMWF-based SHIPS guidance at
72 hours.
Key Messages:
1. A tropical depression is expected to form by Thursday over the
northern Gulf of Mexico. Conditions appear favorable for this system
to strengthen to a hurricane that will bring storm surge, rainfall,
and wind hazards to the central Gulf Coast.
2. A dangerous storm surge is possible in portions of southern and
southeastern Louisiana where a Storm Surge Watch is in effect.
Additional storm surge watches may be needed later tonight or
tomorrow. Residents in these areas should monitor the progress of
this system and listen to any advice given by local officials.
3. A Hurricane Watch has been issued for much of the Louisiana coast
and additional tropical storm or hurricane watches could be needed
later tonight or tomorrow. Residents in the watch area should ensure
they have their hurricane plan in place.
4. The slow movement of this system will result in a long duration
heavy rainfall threat along the central Gulf Coast and inland
through the lower Mississippi Valley through the weekend and
potentially into early next week. Flash flooding and river flooding
will become increasingly likely, some of which may be significant,
especially along and east of the track of the system.
FORECAST POSITIONS AND MAX WINDS
INIT 10/2100Z 28.1N 87.4W 25 KT 30 MPH…POTENTIAL TROP CYCLONE
12H 11/0600Z 27.7N 88.1W 30 KT 35 MPH…POTENTIAL TROP CYCLONE
24H 11/1800Z 27.5N 89.0W 35 KT 40 MPH…TROPICAL STORM
36H 12/0600Z 27.6N 90.2W 40 KT 45 MPH
48H 12/1800Z 28.2N 91.5W 55 KT 65 MPH
72H 13/1800Z 29.3N 92.4W 75 KT 85 MPH
96H 14/1800Z 31.9N 93.0W 55 KT 65 MPH…INLAND
120H 15/1800Z 34.8N 93.1W 25 KT 30 MPH…INLAND
