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Tropical Storm Beryl Forecast Discussion Number 9
2018-07-07 16:47:49| National Hurricane Center (Atlantic)
Issued at 1100 AM AST Sat Jul 07 2018 000 WTNT42 KNHC 071447 TCDAT2 Tropical Storm Beryl Discussion Number 9 NWS National Hurricane Center Miami FL AL022018 1100 AM AST Sat Jul 07 2018 Beryl's small size was always going to make it prone to wild and unpredictable fluctuations in intensity, and that appears to have come to fruition this morning. The cyclone's low-level center is now completely exposed with all associated deep convection displaced to the east and southeast. Dvorak estimates from TAFB and SAB have decreased accordingly, and the initial intensity is set at 55 kt, with Beryl being downgraded to a tropical storm. Even though upper-level winds over the system remain light, and upper-level cloud motions are still from east to west, strengthening low-level flow is likely leading to an increase in the deep-layer westerly shear. In fact, analyses from UW-CIMSS indicate that about 15 kt of westerly shear is now over the system. The shear and a very dry ambient environment have likely caused the small and fragile cyclone to suddenly weaken. Since the low-level flow is expected to increase further, and Beryl will be running into upper-level westerlies in 36-48 hours, the shear is only expected to become more hostile. This will make it extremely difficult for Beryl to become more organized again, and its chances of being a hurricane before reaching the Lesser Antilles have decreased significantly. The updated NHC intensity forecast has been lowered from the previous advisory, and now keeps Beryl as a tropical storm through the forecast period. The forecast intensities could still be a little high, and this prediction will remain low confidence until we get a better handle on Beryl's initial intensity. Even though a 72-hour forecast is provided, it is entirely possible that Beryl will open up into a trough over the eastern Caribbean Sea before that time. Regardless of whether the system has a closed circulation, it is likely to continue producing strong gusty winds and locally heavy rainfall over portions of the Greater Antilles next week. Beryl is now gaining more latitude and has an initial motion of 295/12 kt. The cyclone is still expected to accelerate toward the west-northwest during the next several days, and the track guidance remains tightly clustered through the forecast period. The new NHC track forecast has been shifted slightly northward due to Beryl's recent northwestward jog, and it lies relatively close to the HCCA guidance. Key Messages: 1. Beryl is no longer forecast to be near hurricane strength when it approaches the Lesser Antilles Sunday night or Monday, but the chance of some islands receiving direct impacts from wind and rainfall continues. Tropical storm warnings and watches are in effect for some of the countries in the Lesser Antilles, and additional watches or warnings could be required for other islands later today. 2. Due to its very small size, there is greater-than-usual uncertainty in the analysis of Beryl's current intensity, and confidence in the official intensity forecast is also lower than normal. Rapid changes in intensity, both up and down, that are difficult to predict are possible during the next couple of days. FORECAST POSITIONS AND MAX WINDS INIT 07/1500Z 12.1N 51.1W 55 KT 65 MPH 12H 08/0000Z 12.6N 52.9W 50 KT 60 MPH 24H 08/1200Z 13.6N 56.0W 50 KT 60 MPH 36H 09/0000Z 14.8N 59.6W 50 KT 60 MPH 48H 09/1200Z 15.9N 63.6W 45 KT 50 MPH 72H 10/1200Z 18.3N 71.7W 35 KT 40 MPH...INLAND 96H 11/1200Z...DISSIPATED $$ Forecaster Berg
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