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Tropical Storm Carlos Forecast Discussion Number 5
2021-06-13 22:38:21| National Hurricane Center (East Pacific)
Issued at 200 PM PDT Sun Jun 13 2021 000 WTPZ43 KNHC 132038 TCDEP3 Tropical Storm Carlos Discussion Number 5 NWS National Hurricane Center Miami FL EP032021 200 PM PDT Sun Jun 13 2021 Deep convection has managed to persist over the center of Carlos throughout the day today, although the appearance of this convection has become more ragged as the day has progressed. The blended CI values from TAFB and SAB suggest the system still has an intensity of 45 kt. A recent ASCAT overpass only partially captured the circulation with peak wind vectors of 39 kt. Compensating for possible undersampling by the instrument over only a portion of such a compact cyclone, maintaining 45 kt seems reasonable for the initial advisory intensity. Dry and stable air lies just to the north and west of Carlos, and occasional intrusions of this air into the cyclone's circulation could disrupt convection. However, the overnight diurnal convective maximum could overcome these intrusions over the next couple of nights. Therefore, only slight weakening is indicated through that time period. By 48 h, Carlos is expected to move into the stable airmass which should further disrupt its convection, causing additional weakening. By late in the forecast period the cyclone is forecast to be near or have crossed the 26 degree C SST isotherm. This should cause any remaining convection to gradually dissipate. Although not shown in the official forecast, it is possible Carlos will degenerate into a remnant low by the end of the forecast period, as suggested by the GFS. The latest NHC intensity forecast is very near the various multi-model consensus solutions. Carlos is beginning to show signs of slowing and turning to the left, with the initial motion now 260/6 kt. Model guidance remains in good agreement through 48 h, with the storm slowing and turning west-southwest as a mid-level ridge becomes oriented SW-NE to the north of the cyclone. There is still a vast amount of track guidance spread beyond 72 h, but not as much as earlier today. The GFS, which continues to be the easternmost solution has shifted well west of its previous track, showing Carlos turning northwest in a few days in response to a building ridge to its east, and weakening ridge to the north. The remaining guidance maintains the ridge to the north and shows Carlos turning west by midweek, then west-northwest by late this week. The official NHC forecast is near the previous one through 48 h. Beyond 48 h, large adjustments were required to accommodate the continuing westward trends in the guidance. Despite the abrupt shift in the official forecast for the latter half of the period, it remains well east of the consensus and the majority of available track guidance. FORECAST POSITIONS AND MAX WINDS INIT 13/2100Z 11.7N 126.6W 45 KT 50 MPH 12H 14/0600Z 11.4N 127.4W 40 KT 45 MPH 24H 14/1800Z 11.0N 128.3W 40 KT 45 MPH 36H 15/0600Z 10.6N 129.2W 40 KT 45 MPH 48H 15/1800Z 10.4N 130.0W 35 KT 40 MPH 60H 16/0600Z 10.3N 130.8W 30 KT 35 MPH 72H 16/1800Z 10.3N 131.3W 30 KT 35 MPH 96H 17/1800Z 10.7N 132.0W 25 KT 30 MPH 120H 18/1800Z 11.4N 132.7W 25 KT 30 MPH $$ Forecaster Latto
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