[Tropical] Tropical Cyclone Discussion

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WTNT43 KNHC 062046
TCDAT3

Tropical Storm Cristobal Discussion Number  21
NWS National Hurricane Center Miami FL       AL032020
400 PM CDT Sat Jun 06 2020

Cristobal continues to lack the appearance and structure of a
typical tropical cyclone.  In fact,  the large radius of maximum
wind and convective bands well removed from the center are more
characteristic of a subtropical cyclone.  Based on earlier Air
Force Hurricane Hunter observations, the maximum winds are about 45
kt.  The central pressure has held steady during the last couple of
fixes of the aircraft mission, suggesting no significant
strengthening since this morning.  Since the system is not well
organized and is likely to continue to ingest some more dry air,
only a little more strengthening is expected until landfall.  The
official intensity forecast is unchanged and remains close to the
model consensus.

The cyclone remains on track and is moving northward, or 360/10 kt.
The track forecast philosophy remains unchanged.  The system should
continue northward between two mid-level anticyclones until it
nears the northern Gulf coast.  After landfall, a slight building of
a ridge to the northeast should induce a turn toward the
north-northwest.  In 3-4 days, the post-tropical cyclone should
accelerate north-northeastward ahead of a mid-tropospheric trough.
Thereafter, the global models suggest that the system should merge
with an extratropical cyclone near the Great Lakes.  The official
track forecast is in good agreement with the dynamical model
consensus and is also close to the latest GFS solution.

Cristobal is likely to remain a broad and asymmetric storm when it
makes landfall.  Therefore, one should not focus on the exact
forecast track, as the associated winds, storm surge, and rainfall
will extend well away the center.


Key Messages:

1. There is a danger of life-threatening storm surge outside of the
Hurricane and Storm Damage Risk Reduction System from the Mouth of
the Mississippi River to Ocean Springs, Mississippi, and a Storm
Surge Warning is in effect for those areas.  Life-threatening storm
surge remains possible in other portions of southern and
southeastern Louisiana where a Storm Surge Watch is in effect.
Residents in these locations should follow advice given by local
emergency officials.

2. Tropical storm force winds are expected by late tonight along the
northern Gulf Coast from central Louisiana to the western Florida
Panhandle, including metropolitan New Orleans, and a Tropical Storm
Warning is in effect for this area.  These winds will arrive well
in advance of and extend well east of Cristobal’s center.

3. Heavy rainfall will continue across west and north Florida today,
spreading from east to west across the eastern and central Gulf
Coast from the Florida Panhandle into Louisiana today into Sunday.
This heavy rain will move into the Lower Mississippi Valley on
Monday. Significant flooding will be possible on smaller streams,
especially where heavier rainfall occurs over portions of the Gulf
Coast and Lower Mississippi Valley.

FORECAST POSITIONS AND MAX WINDS

INIT  06/2100Z 25.2N  90.2W   45 KT  50 MPH
 12H  07/0600Z 26.7N  90.2W   50 KT  60 MPH
 24H  07/1800Z 28.5N  90.4W   50 KT  60 MPH
 36H  08/0600Z 30.6N  91.1W   40 KT  45 MPH...INLAND
 48H  08/1800Z 33.0N  92.3W   30 KT  35 MPH...INLAND
 60H  09/0600Z 36.0N  92.8W   25 KT  30 MPH...INLAND
 72H  09/1800Z 40.5N  91.5W   20 KT  25 MPH...POST-TROP/INLAND
 96H  10/1800Z 49.0N  88.0W   20 KT  25 MPH...POST-TROP/EXTRATROP
120H  11/1800Z...MERGED WITH EXTRATROPICAL LOW

$$
Forecaster Pasch

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