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| #1003757 (Received by flhurricane at: 4:48 AM 06.Jun.2020) 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 |