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Tropical Depression Three Forecast Discussion Number 3
2020-06-02 10:50:04| National Hurricane Center (Atlantic)
Issued at 400 AM CDT Tue Jun 02 2020 785 WTNT43 KNHC 020849 TCDAT3 Tropical Depression Three Discussion Number 3 NWS National Hurricane Center Miami FL AL032020 400 AM CDT Tue Jun 02 2020 Satellite data, Mexican radar data from Sabancuy, and nearby surface observations indicate that the depression has become a little better organized and has strengthened slightly since the previous advisory. Radar data indicate a mass of convection has developed north of and over the low-level center, and a broken curved band has also formed in the eastern semicircle. The initial intensity has been increased to 30 kt based on a 0201 UTC ASCAT-A overpass that showed a couple of 27-kt vectors located in the northeastern quadrant outside of the most active convection. An Air Force Reserve reconnaissance aircraft is scheduled to investigate the depression later this morning. The initial motion is westward or 270/02 kt. The latest 00Z model guidance continues to show the depression remaining embedded within the larger Central American gyre for the next few days, with the gyre gradually contracting around the depression, with the two entities merging into one system by 72 hours. Similar to last night, tonight's model runs have again abandoned the development of a secondary low east of the depression and moving it northward toward the U. S Gulf coast. This may be due in part to the lack of Mexican and Central American upper-air data at 0000 UTC, except for the Belize sounding. But the global and regional models are in overall in good agreement on the cyclone remaining trapped in a break in the subtropical ridge to the east and west of the depression. By 72-96 hours, a weak shortwave trough is forecast to drop southward out of the southern plains and into into the ridge weakness and act as a catalyst to nudge the depression slowly northward on days 4 and 5. Until that time, the cyclone is expected to meander over the the Bay of Campeche for the next 2-3 days, possibly making landfall along the coast of extreme southeastern Mexico and the west coast of Yucatan. The new NHC forecast track is similar to the previous advisory track, and brings the center close to the coast of Mexico on days 2 and 3. It should be noted, though, that in 5 days there could be a cyclone near the forecast point that is not actually TD-3 due to land interaction and the possible formation of a secondary cyclone. Although the vertical wind shear is forecast to remain low while the cyclone remains trapped in the Bay of Campeche during the next few days, only slow strengthening is expected due to possible land interaction and intrusions of dry air caused by southwesterly downslope flow coming off of the mountains in the state of Chiapas, which already appears to be underway based on satellite and radar imagery. After the cyclone starts moving northward, increasing southerly shear is expected to inhibit any significant or rapid strengthening. An alternative intensity forecast scenario is that the cyclone moves far enough inland over Mexico to dissipate completely in less than 5 days as forecast by the GFS and HWRF models. Given the complexity of the situation, both the track and intensity forecasts are currently low confidence. However, either of the current scenarios will result in widespread heavy rains over portions of southern Mexico and Central America. Key Messages: 1. Deadly flooding has already been occurring in portions of Guatemala and El Salvador. The depression is expected to bring heavy rainfall to portions of southern Mexico, Guatemala, Honduras and El Salvador, which could cause life-threatening flash flooding and mudslides. Refer to products from your local weather office for more information. 2. Tropical storm conditions are expected along the coast of Mexico where a tropical storm warning is in effect. 3. The system is forecast to begin moving northward across the Gulf of Mexico later this week. However, it is too soon to specify the location and timing of any potential impacts along the U.S. Gulf Coast. Interests in these areas should monitor the progress of this system through the week and ensure they have their hurricane plan in place as we begin the season. FORECAST POSITIONS AND MAX WINDS INIT 02/0900Z 19.6N 92.1W 30 KT 35 MPH 12H 02/1800Z 19.5N 92.4W 35 KT 40 MPH 24H 03/0600Z 19.1N 92.7W 40 KT 45 MPH 36H 03/1800Z 18.8N 92.7W 40 KT 45 MPH 48H 04/0600Z 18.7N 92.5W 45 KT 50 MPH 60H 04/1800Z 19.0N 92.3W 45 KT 50 MPH 72H 05/0600Z 19.3N 92.1W 45 KT 50 MPH 96H 06/0600Z 20.7N 91.7W 50 KT 60 MPH 120H 07/0600Z 23.5N 91.2W 55 KT 65 MPH $$ Forecaster Stewart
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