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Tropical Storm Carlos Forecast Discussion Number 4
2021-06-13 16:48:16| National Hurricane Center (East Pacific)
Issued at 800 AM PDT Sun Jun 13 2021 000 WTPZ43 KNHC 131448 TCDEP3 Tropical Storm Carlos Discussion Number 4 NWS National Hurricane Center Miami FL EP032021 800 AM PDT Sun Jun 13 2021 Deep convection has persisted over the center of Carlos throughout the night and a new convective burst with cloud tops of -60 to -70 degrees C is occuring over the estimated center location. A blend of the latest Dvorak intensity estimates from TAFB and SAB support increasing the initial intensity to 45 kt. This seems reasonable, as an earlier ASCAT-B overpass had several vectors of 40-41 kt, and the vortex likely has spun up further due to the ongoing deep convection. Carlos continues to move west at around 7 kt, steered by a mid-level ridge to the north. This ridge is forecast to become oriented northeast to southwest later today and prevail over the next couple days which should cause the cyclone to move slowly west-southwestward. After 48 h the models diverge significantly in their track solutions, with the GFS and ECMWF turning the system abruptly northward, while most of the other guidance has a more westward then west-northwestward motion beyond 72 h. There is a mid- to upper-level low currently located west of Mexico that the models are handling differently. The easternmost track solutions for Carlos weaken this feature more quickly and replace it with a ridge to the east of Carlos, while the western solutions keep the feature around, delaying the more poleward motion of the cyclone. The latest NHC track forecast is near the previous one through 48 h, but is shifted west thereafter. Still, the NHC forecast track is well east of the consensus after 48 h. Needless to say the track forecast confidence beyond day 2 is low. Northerly shear of 10-15 kt and the proximity to dry and stable mid-level air to its north should cause periodic weakening of the storm's deep convection, which would prevent any further strengthening, and Carlos is expected to hold its current intensity for the next couple of days. Thereafter, regardless of the western or eastern track model solutions, Carlos is expected to encounter an even drier and more stable airmass and cooler sea surface temperatures. This should cause a weakening trend to begin by mid-week. The latest NHC intensity forecast is little changed from the previous one, and is close to the multi-model consensus. FORECAST POSITIONS AND MAX WINDS INIT 13/1500Z 11.8N 126.0W 45 KT 50 MPH 12H 14/0000Z 11.6N 126.7W 45 KT 50 MPH 24H 14/1200Z 11.1N 127.5W 45 KT 50 MPH 36H 15/0000Z 10.7N 128.0W 45 KT 50 MPH 48H 15/1200Z 10.4N 128.5W 45 KT 50 MPH 60H 16/0000Z 10.4N 129.0W 40 KT 45 MPH 72H 16/1200Z 11.0N 129.4W 35 KT 40 MPH 96H 17/1200Z 12.8N 129.6W 30 KT 35 MPH 120H 18/1200Z 15.2N 129.4W 30 KT 35 MPH $$ Forecaster Latto
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