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Tropical Storm Beryl Forecast Discussion Number 3

2018-07-06 04:31:58| National Hurricane Center (Atlantic)

Issued at 1100 PM AST Thu Jul 05 2018 000 WTNT42 KNHC 060231 TCDAT2 Tropical Storm Beryl Discussion Number 3 NWS National Hurricane Center Miami FL AL022018 1100 PM AST Thu Jul 05 2018 Tiny Beryl has maintained a small ball of convection near the center except for a brief period around 2300 UTC when a tight curved band was exposed, revealing 10- to 11-tenths banding. Passive microwave satellite data during the past 6 hours have also indicated 5-nmi-diameter eye exists underneath the CDO feature. Given the small size of the cyclone, which can quickly adjust to convective changes, and a Dvorak satellite estimate of T3.5/55 kt from SAB, the advisory intensity has been increased to 55 kt. The initial motion estimate is 275/12 kt. Most of the latest model guidance has made a pronounced southward shift, which is significant since all of the models have displayed a distinct right-of-track, poleward bias over the past 48 hours. The ECMWF has had the greatest poleward bias, and is now the northernmost solution in the model suite. The GFS, HWRF, and UKMET are now clustered along the southern edge of the guidance envelope, with the consensus models somewhere in between those latter models and the ECMWF. Given the very small size of Beryl, I am having difficulty envisioning the cyclone moving into the strong subtropical ridge situated to its north and gaining as much latitude as the ECMWF has been and is still indicating. As a result, the new NHC forecast track has been shifted south of the previous advisory track, but not as far south as the GFS-HRWF-UKMET consensus, and lies a tad south of the HCCA and FSSE solutions. Water vapor and model moisture analyses indicate that Beryl has been able to maintain a buffer between it and the very dry, stable air just to its north, due in large part to the deep, southerly moisture fetch coming up from the equatorial region. This pattern is forecast by most of the global models to continue for at least the next 48 hours. That favorable environment, coupled with forecast low vertical wind shear conditions of near 5 kt for the next 24 hours, should allow Beryl to achieve hurricane status by late Friday. By 72 hours when Beryl will be approaching the Lesser Antilles, the shear is forecast to increase from the west and northwest at 20-25 kt, which is expected to induce rapid weakening. All of the global models continue to show the cyclone opening up into a tropical wave shortly after 72 hours, which is what the current forecast continues to depict in order to maintain continuity with the previous advisory track. However, only a slight delay in the onset of the strong shear conditions could result in Beryl maintaining tropical cyclone status when it moves across the Lesser Antilles on Sunday. Even though Beryl is expected to dissipate just east of the Lesser Antilles early next week, the remnant tropical wave will continue moving quickly westward and will likely bring locally heavy rains and strong gusty winds to portions of the Leeward Islands on Sunday and Monday. Key Messages: 1. Due to its very small size, there is greater-than-usual uncertainty in the analysis of Beryl's current intensity. Confidence in the official intensity forecast is also much lower than normal. Rapid changes in intensity, both up and down, that are difficult to predict are possible during the next couple of days. 2. While Beryl is still expected to dissipate as a tropical cyclone by Monday before reaching the Lesser Antilles, there will likely be some rain and wind impacts on those islands early next week. Residents there should monitor products from their local weather office for more information. FORECAST POSITIONS AND MAX WINDS INIT 06/0300Z 10.4N 44.0W 55 KT 65 MPH 12H 06/1200Z 10.7N 45.5W 60 KT 70 MPH 24H 07/0000Z 11.2N 47.4W 65 KT 75 MPH 36H 07/1200Z 11.9N 49.7W 65 KT 75 MPH 48H 08/0000Z 12.7N 52.5W 60 KT 70 MPH 72H 09/0000Z 14.4N 59.7W 50 KT 60 MPH 96H 10/0000Z...DISSIPATED $$ Forecaster Stewart

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Tropical Storm Fabio Forecast Discussion Number 21

2018-07-05 22:33:51| Tropical Depression LIDIA

Issued at 200 PM PDT Thu Jul 05 2018

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Tropical Storm Beryl Forecast Discussion Number 2

2018-07-05 22:18:52| National Hurricane Center (Atlantic)

Issued at 500 PM AST Thu Jul 05 2018 000 WTNT42 KNHC 052018 TCDAT2 Tropical Storm Beryl Discussion Number 2 NWS National Hurricane Center Miami FL AL022018 500 PM AST Thu Jul 05 2018 Beryl has been a bit of a surprise today, which is not uncommon for tiny tropical cyclones such as itself. A 1724 UTC SSMI microwave pass and a 1853 UTC SSMI/S pass both revealed that the cyclone had developed a well-defined 5 nmi-wide mid-level eye, and a dimple has been apparent in visible satellite imagery. It's usually difficult to get a good handle on the intensity of these types of cyclones given their small size, but data-T numbers from TAFB and SAB are a consensus T3.0. The initial intensity is therefore raised to 45 kt, but there is a lot of uncertainty in this estimate. If the initial intensity is uncertain, the future intensity is even more of a quandary. Despite being surrounded by abundant dry air, Beryl has apparently been able to isolate itself and possibly moisten the near-storm environment while located in an area of low shear. Since the shear is expected to remain quite low for the next 36 hours or so, and small cyclones like Beryl often have a tendency to strengthen quickly over a short period of time, continued intensification appears likely for the next day or so. The updated NHC intensity forecast most closely follows the statistical- dynamical guidance, which lies at the upper end of the guidance envelope, and brings Beryl to hurricane strength within 36 hours. After that time, increasing westerly shear, partially due to Beryl accelerating toward the west, is expected to cause weakening. In addition, every global model shows the cyclone opening up into a tropical wave in 72-96 hours, which is what the NHC forecast continues to depict. It cannot be stressed enough, however, that this is a low confidence forecast. The one stable part of the forecast is Beryl's future track. The new guidance has not changed much from the previous forecast cycle, and it continues to show Beryl slowing down a bit during the next 24 hours, followed by a west-northwestward acceleration in 48-72 hours due to a strengthening ridge to the north. The updated NHC track forecast is just a bit south of the previous one and is closest to the HCCA and Florida State Superensemble guidance. Even though Beryl is expected to dissipate just east of the Lesser Antilles early next week, the remnant tropical wave will continue moving quickly westward and will likely bring locally heavy rains and gusty winds to portions of the Leeward Islands on Sunday and Monday. Key Messages: 1. Due to its very small size, there is greater-than-usual uncertainty in the analysis of Beryl's current intensity. Confidence in the official intensity forecast is also much lower than normal. Rapid changes in intensity, both up and down, that are difficult to predict are possible during the next couple of days. 2. While Beryl is still expected to dissipate as a tropical cyclone by Monday before reaching the Lesser Antilles, there will likely be some rain and wind impacts on those islands early next week. Residents there should monitor products from their local weather office for more information. FORECAST POSITIONS AND MAX WINDS INIT 05/2100Z 10.3N 42.8W 45 KT 50 MPH 12H 06/0600Z 10.8N 44.5W 55 KT 65 MPH 24H 06/1800Z 11.4N 46.3W 60 KT 70 MPH 36H 07/0600Z 12.1N 48.3W 65 KT 75 MPH 48H 07/1800Z 13.0N 51.0W 60 KT 70 MPH 72H 08/1800Z 14.5N 58.4W 50 KT 60 MPH 96H 09/1800Z...DISSIPATED $$ Forecaster Berg

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Tropical Depression Two Forecast Discussion Number 1

2018-07-05 16:43:17| National Hurricane Center (Atlantic)

Issued at 1100 AM AST Thu Jul 05 2018 000 WTNT42 KNHC 051443 TCDAT2 Tropical Depression Two Discussion Number 1 NWS National Hurricane Center Miami FL AL022018 1100 AM AST Thu Jul 05 2018 For the past day or so, we've been monitoring a small area of low pressure associated with a tropical wave over the tropical Atlantic Ocean. Despite a noticeable mid-level rotation in the convective clouds, it had not been conclusive whether or not the system had a closed circulation at the surface with a well-defined center. However, the system appears more distinct and independent from the Intertropical Convergence Zone as compared to yesterday, and scatterometer data appears conclusive enough to support a closed, yet tiny circulation. We are now confident enough that the system meets the criteria of a tropical cyclone, and have initiated advisories on Tropical Depression Two with maximum winds of 30 kt, which is supported by Dvorak classifications from TAFB and SAB. The depression will be located in a relatively low-shear environment for the next 3 days or so. However, the small cyclone is surrounded by abundant dry air, and the system will be moving over marginally warm waters during the next few days, which could both limit intensification. The NHC official forecast allows for some slight strengthening and most closely follows the HFIP Corrected Consensus guidance (HCCA), showing the depression becoming a tropical storm within the next 24 hours. Between 72 and 96 hours, the system is expected to begin encountering strong westerly shear and also accelerate, both of which should cause it to degenerate into an open wave east of the Lesser Antilles. Even though the center has been difficult to locate, the initial motion is estimated to be westward, or 270/14 kt. The depression is located to the south of a sprawling subtropical ridge, although a break in the ridge over the central Atlantic may cause the system to slow down a bit during the next 36 hours. After that time, the cyclone is likely to speed up again when it becomes situated to the south of a new mid-level high. The track guidance is in generally good agreement, and the NHC official forecast is close to the TVCX multi-model consensus and the HCCA guidance. Even though the cyclone is expected to dissipate east of the Lesser Antilles early next week, the remnant tropical wave will continue moving quickly westward, likely bringing locally heavy rains and gusty winds to portions of the Leeward Islands on Sunday and Monday. FORECAST POSITIONS AND MAX WINDS INIT 05/1500Z 10.2N 41.4W 30 KT 35 MPH 12H 06/0000Z 10.7N 43.1W 30 KT 35 MPH 24H 06/1200Z 11.4N 45.2W 35 KT 40 MPH 36H 07/0000Z 12.1N 47.2W 35 KT 40 MPH 48H 07/1200Z 12.9N 49.6W 35 KT 40 MPH 72H 08/1200Z 14.7N 56.6W 35 KT 40 MPH 96H 09/1200Z...DISSIPATED $$ Forecaster Berg

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Tropical Storm Fabio Forecast Discussion Number 20

2018-07-05 16:37:48| Tropical Depression LIDIA

Issued at 800 AM PDT Thu Jul 05 2018

Tags: number discussion storm tropical

 

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