Issued at 400 AM CDT Tue Jun 02 2020

785
WTNT43 KNHC 020849
TCDAT3

Tropical Depression Three Discussion Number

3
NWS National Hurricane Center Miami FL

AL032020
400 AM CDT Tue Jun 02 2020

Satellite data, Mexican radar data from Sabancuy, and nearby surface
observations indicate that the depression has become a little better
organized and has strengthened slightly since the previous advisory.

Radar data indicate a mass of convection has developed north of and
over the low-level center, and a broken curved band has also formed
in the eastern semicircle. The initial intensity has been increased
to 30 kt based on a 0201 UTC ASCAT-A overpass that showed a couple
of 27-kt vectors located in the northeastern quadrant outside of the
most active convection. An Air Force Reserve reconnaissance
aircraft is scheduled to investigate the depression later this
morning.

The initial motion is westward or 270/02 kt. The latest 00Z model
guidance continues to show the depression remaining embedded within
the larger Central American gyre for the next few days, with the
gyre gradually contracting around the depression, with the two
entities merging into one system by 72 hours. Similar to last
night, tonight's model runs have again abandoned the development of
a secondary low east of the depression and moving it northward
toward the U. S Gulf coast. This may be due in part to the lack of
Mexican and Central American upper-air data at 0000 UTC, except for
the Belize sounding. But the global and regional models are in
overall in good agreement on the cyclone remaining trapped in a
break in the subtropical ridge to the east and west of the
depression. By 72-96 hours, a weak shortwave trough is forecast to
drop southward out of the southern plains and into into the ridge
weakness and act as a catalyst to nudge the depression slowly
northward on days 4 and 5. Until that time, the cyclone is
expected to meander over the the Bay of Campeche for the next 2-3
days, possibly making landfall along the coast of extreme
southeastern Mexico and the west coast of Yucatan. The new NHC
forecast track is similar to the previous advisory track, and
brings the center close to the coast of Mexico on days 2 and 3. It
should be noted, though, that in 5 days there could be a cyclone
near the forecast point that is not actually TD-3 due to land
interaction and the possible formation of a secondary cyclone.

Although the vertical wind shear is forecast to remain low while the
cyclone remains trapped in the Bay of Campeche during the next few
days, only slow strengthening is expected due to possible land
interaction and intrusions of dry air caused by southwesterly
downslope flow coming off of the mountains in the state of Chiapas,
which already appears to be underway based on satellite and radar
imagery. After the cyclone starts moving northward, increasing
southerly shear is expected to inhibit any significant or rapid
strengthening. An alternative intensity forecast scenario is that
the cyclone moves far enough inland over Mexico to dissipate
completely in less than 5 days as forecast by the GFS and HWRF
models.

Given the complexity of the situation, both the track and intensity
forecasts are currently low confidence. However, either of the
current scenarios will result in widespread heavy rains over
portions of southern Mexico and Central America.

Key Messages:

1. Deadly flooding has already been occurring in portions of
Guatemala and El Salvador. The depression is expected to bring
heavy rainfall to portions of southern Mexico, Guatemala, Honduras
and El Salvador, which could cause life-threatening flash flooding
and mudslides. Refer to products from your local weather office for
more information.

2. Tropical storm conditions are expected along the coast of Mexico
where a tropical storm warning is in effect.

3. The system is forecast to begin moving northward across the Gulf
of Mexico later this week. However, it is too soon to specify the
location and timing of any potential impacts along the U.S. Gulf
Coast. Interests in these areas should monitor the progress of this
system through the week and ensure they have their hurricane plan in
place as we begin the season.

FORECAST POSITIONS AND MAX WINDS

INIT 02/0900Z 19.6N 92.1W

30 KT 35 MPH
12H 02/1800Z 19.5N 92.4W

35 KT 40 MPH
24H 03/0600Z 19.1N 92.7W

40 KT 45 MPH
36H 03/1800Z 18.8N 92.7W

40 KT 45 MPH
48H 04/0600Z 18.7N 92.5W

45 KT 50 MPH
60H 04/1800Z 19.0N 92.3W

45 KT 50 MPH
72H 05/0600Z 19.3N 92.1W

45 KT 50 MPH
96H 06/0600Z 20.7N 91.7W

50 KT 60 MPH
120H 07/0600Z 23.5N 91.2W

55 KT 65 MPH

$$
Forecaster Stewart

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