[Tropical] Tropical Cyclone Discussion

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WTNT43 KNHC 030847
TCDAT3

Tropical Storm Cristobal Discussion Number   7
NWS National Hurricane Center Miami FL       AL032020
400 AM CDT Wed Jun 03 2020

Cristobal has continued to get better organized this morning with
the development of a small CDO feature over the low-level center,
with cloud tops of -82C to -86C developing very near the center.
Radar data from Sabancuy, Mexico, also has shown an improvement in
the central convective features, along with an increase in
convective banding on the west side of the circulation, which
previously had been devoid of any significant convection.  Reports
from nearby Mexican observations indicate that winds of 47-48 kt
exist west of the center, which supports an intensity of 50 kt. The
same observations support a minimum pressure of 994 mb.

The aforementioned surface observation data and radar imagery
indicate that Cristobal is now moving southeastward or 140/03 kt.
There could be some erratic motion this morning due to land
interaction with the inner-core wind field, but the general motion
should remain southeastward toward the coast of Mexico. By this
afternoon, a turn toward the east is expected, driving the cyclone
inland over southeastern Mexico where it could meander for the next
day or two. By 48 hours, the global and regional models are in good
agreement on the development of a long fetch of southerly flow on
the east side of Cristobal between the cyclone's center and a ridge
over the Bahamas and Hispaniola, which will act to lift the tropical
storm slowly northward toward the south-central Gulf of Mexico. By
72 hours and beyond, mid-latitude ridging amplifies over the
southeastern U.S. and the Bahamas, which will increase the southerly
steering flow, causing Cristobal to accelerate northward on day 4
over the central Gulf, followed by a turn toward the north-northwest
on day 5 near the south-central U.S. Gulf coast. The models are
in very good agreement on this overall developing scenario, with
only timing differences on when and how fast the cyclone will lift
out away from Mexico. The new NHC track forecast is similar to the
previous advisory track, and closely follows a blend of the
consensus models TVCN and NOAA-HCCA.

Some additional slight strengthening remains possible this morning
before Cristobal moves inland over southeastern Mexico.  Weakening
is likely this afternoon and tonight while the circulation after
landfall. The intensity forecast leans heavily on just how far
inland Cristobal moves. For now, the cyclone is expected to remain
relatively close to the warm Gulf waters, which should temper the
rate of weakening typically experienced by inland tropical cyclones.
But if Cristobal moves as far inland as Guatemala like the ECMWF and
GFS models are forecasting, the cyclone would be considerably weaker
and the wind field more expansive on days 3-5. The official
intensity forecast is basically the same as the previous advisory,
and closely follows the intensity consensus models IVCN and HCCA.


Key Messages:

1. Damaging and deadly flooding has already occurred in portions of
Mexico and Central America.  Cristobal is expected to produce
additional extreme rainfall amounts through the end of the week.
The heaviest additional rainfall is expected over far southern
Mexico and portions of the Yucatan Peninsula, while also extending
along the Pacific coast from Chiapas to Guatemala and El Salvador.
This rainfall could cause widespread life-threatening flash floods
and mudslides.

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

3. Cristobal is forecast to begin moving northward across the Gulf
of Mexico on Friday, and there is a risk of storm surge, rainfall,
and wind impacts this weekend along portions of the U.S. Gulf Coast
from Texas to the Florida Panhandle. While it is too soon to
determine the exact location, timing, and magnitude of these
impacts, interests in these areas should monitor the progress of
Cristobal and ensure they have their hurricane plan in place.


FORECAST POSITIONS AND MAX WINDS

INIT  03/0900Z 18.9N  92.0W   50 KT  60 MPH
 12H  03/1800Z 18.5N  91.8W   45 KT  50 MPH...INLAND
 24H  04/0600Z 18.3N  91.5W   35 KT  40 MPH...INLAND
 36H  04/1800Z 18.5N  91.1W   30 KT  35 MPH...INLAND
 48H  05/0600Z 19.3N  91.0W   30 KT  35 MPH...OVER WATER
 60H  05/1800Z 20.5N  90.9W   35 KT  40 MPH
 72H  06/0600Z 22.2N  90.9W   40 KT  45 MPH
 96H  07/0600Z 26.3N  90.5W   50 KT  60 MPH
120H  08/0600Z 29.8N  91.6W   55 KT  65 MPH...INLAND

$$
Forecaster Stewart
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