[Tropical] Tropical Cyclone Discussion

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WTNT43 KNHC 070845
TCDAT3

Tropical Storm Cristobal Discussion Number  23
NWS National Hurricane Center Miami FL       AL032020
400 AM CDT Sun Jun 07 2020

Cristobal continues to resemble a subtropical cyclone more than a
tropical cyclone.  The convection near the center remains limited,
although it has become a little better organized during the past
several hours.  In addition, aircraft and scatterometer data show
that the radius of maximum winds remains at or above 90 n mi.
These data also suggest that a 45 kt intensity may be a bit
generous, but since the central pressure remains near 993 mb the
intensity has not changed for this advisory.

The initial motion is 360/10 between a deep-layer ridge to
Cristobal's east and a mid- to upper-level trough over the western
Gulf of Mexico.  This general motion should continue for 12-18 h,
followed by a turn toward the north-northwest due to a mid-latitude
ridge passing north of the cyclone.  After 36 h, a turn toward the
north and north-northeast is expected as Cristobal or its remnants
encounter the mid-latitude westerlies.  There are no important
changes to either the track guidance or the forecast track since the
last advisory.

The broad nature of the cyclone and significant dry air entrainment
is likely to prevent intensification before landfall, and the new
intensity forecast holds the intensity constant at 45 kt until
that time.  Weakening is expected after landfall, with Cristobal
weakening below tropical-storm strength just after the 24 h point.
The new intensity forecast shows slight re-intensification as the
system become extratropical at 72-96 h in agreement with the global
model guidance.

Cristobal remains a broad and asymmetric storm.  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 should spread along the northern Gulf
coast from central Louisiana to the western Florida Panhandle,
including metropolitan New Orleans today, 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 north Florida this morning,
spreading from east to west across the eastern and central Gulf
Coast from the Florida Panhandle into Louisiana today. The Central
Gulf Coast region will be most prone to issues after the passage of
the center of Cristobal from Sunday night into Monday. This heavy
rain will move up the Lower and Mid Mississippi Valley Monday into
Tuesday, then across the Upper Mississippi Valley and Northern
Plains Tuesday and Tuesday night. Flash flooding, and new and
renewed significant river flooding is possible, especially where
heavier rainfall occurs over portions of the Gulf Coast through the
Mississippi Valley.


FORECAST POSITIONS AND MAX WINDS

INIT  07/0900Z 27.3N  90.1W   45 KT  50 MPH
 12H  07/1800Z 28.7N  90.3W   45 KT  50 MPH
 24H  08/0600Z 30.8N  91.2W   35 KT  40 MPH...INLAND
 36H  08/1800Z 33.3N  92.3W   30 KT  35 MPH...INLAND
 48H  09/0600Z 36.6N  92.6W   25 KT  30 MPH...INLAND
 60H  09/1800Z 40.9N  91.4W   25 KT  30 MPH...INLAND
 72H  10/0600Z 46.0N  89.0W   30 KT  35 MPH...POST-TROP/EXTRATROP
 96H  11/0600Z 52.0N  84.5W   30 KT  35 MPH...POST-TROP/EXTRATROP
120H  12/0600Z...MERGED WITH EXTRATROPICAL LOW

$$
Forecaster Beven

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