Tropical Storm Cristobal Forecast Discussion Number 19

By | June 6, 2020

Issued at 400 AM CDT Sat Jun 06 2020


000
WTNT43 KNHC 060841
TCDAT3
 
Tropical Storm Cristobal Discussion Number  19
NWS National Hurricane Center Miami FL       AL032020
400 AM CDT Sat Jun 06 2020

Satellite imagery this morning shows that Cristobal does not have a 
classic tropical cyclone structure, probably due to interaction with 
a mid- to upper-level trough and the associated entrainment of dry 
air.  The circulation is elongated north-south near the center, and 
multiple low-cloud swirls are preset.  In addition, the strongest 
convection is well removed from the center of Cristobal to the north 
and east.  The initial intensity is held at 40 kt based on earlier 
scatterometer data and continuity from the previous advisory.

The initial motion is now 350/12.  There is no change in the track 
forecast philosophy from the previous advisory.  A south to north 
steering flow between a deep-layer ridge over the western Atlantic 
and the aforementioned trough over the western Gulf of Mexico 
should cause Cristobal to continue moving generally northward for 
the next 36 h or so.  This motion should take the center of the 
storm across the Louisiana coast by Sunday night.  Around the 
landfall time, a slight turn to the northwest is expected as a 
mid-level ridge moves across the central and eastern U.S. to the 
north of the cyclone.  Overall, the models remain in good 
agreement, although the GFS and ECMWF have shifted a little to the 
left of their previous forecasts.  The new official forecast is 
similar to the previous forecast and lies near the various 
consensus models.
 
Cristobal is expected to slowly strengthen until it makes landfall 
along the northern Gulf coast in a couple of days.  However, the 
broad structure of the cyclone, the dry air entrainment, and 
moderate wind shear should prevent a significant amount of 
intensification.  One change from the previous forecast is that the 
global models suggest that Cristobal will undergo extratropical 
transition over the upper Mississippi River valley in about 4 days, 
and it should persist a little longer than previously forecast.
 
Cristobal is likely to remain a broad and asymmetric storm when it
makes landfall.  Therefore, users are urged to not focus on the
exact forecast path as the associated winds, storm surge, and
rainfall will extend well to the east of the center.
 
Key Messages:
 
1. Damaging and deadly flooding was already occurring in portions of 
Mexico and Central America. Additional rainfall from Cristobal will 
continue to slowly subside, however life threatening flash floods 
and mudslides will still be possible into Saturday. Refer to 
products from your local weather office for more information.
 
2. 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 along the Florida Big Bend and 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.
 
3. Tropical storm force winds are expected by late Saturday night
along the northern Gulf Coast from southeastern 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 Cristobals
center.
 
4. Heavy rainfall will spread into portions of the Gulf Coast, 
from east Texas to Florida, this weekend into early next week, with 
areas of flash flooding. Significant flooding will be possible on 
the smaller tributaries, especially where heavier rainfall occurs 
over portions of the Mid-South and Gulf Coast.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  06/0900Z 23.8N  90.2W   40 KT  45 MPH
 12H  06/1800Z 25.0N  90.4W   45 KT  50 MPH
 24H  07/0600Z 26.8N  90.4W   50 KT  60 MPH
 36H  07/1800Z 28.8N  90.5W   50 KT  60 MPH
 48H  08/0600Z 30.6N  91.3W   40 KT  45 MPH...INLAND
 60H  08/1800Z 33.2N  92.1W   30 KT  35 MPH...INLAND
 72H  09/0600Z 36.4N  92.4W   25 KT  30 MPH...INLAND
 96H  10/0600Z 45.0N  89.0W   25 KT  30 MPH...POST-TROP/EXTRATROP
120H  11/0600Z 52.5N  83.5W   25 KT  30 MPH...POST-TROP/EXTRATROP
 
$$
Forecaster Beven
 

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