Hurricane Sam Forecast To Remain A Major Hurricane Through The Next 3 Days

What you need to know:
– Sam is forecast to continue moving northeast of the Lesser Antilles, safely northeast of the Leeward Islands, posing no direct threat to T&T and the Lesser Antilles.
– The National Hurricane Center is forecasting Sam to remain at Category 4 strength, with fluctuations in intensity through the next 48 hours.
Swells from Hurricane Sam are forecast to continue affecting the northern and eastern coastlines of the Lesser Antilles through the end of the week.
– Due to near calm winds induced by Sam, very hot temperatures are forecast across the region with localized, slow-moving, possibly severe, afternoon showers and thunderstorms across western and hilly areas.

The Latest From The National Hurricane Center

Hurricane Sam's Forecast Track as of 11:00 AM Wednesday 29th September 2021. (National Hurricane Center)
Hurricane Sam’s Forecast Track as of 11:00 AM Wednesday 29th September 2021. (National Hurricane Center)

At 11:00 AM AST, the center of Hurricane Sam was located near latitude 19.4°N, 57.0°W. Sam is moving toward the northwest near 15 KM/H, and this general motion with an increase in forward speed is expected during the next couple of days. A turn toward the north is forecast by Friday. On the forecast track, Sam will pass well to the east-northeast of the northern Leeward Islands through tonight.

Maximum sustained winds are near 215 KM/H with higher gusts. Sam is a Category 4 hurricane on the Saffir-Simpson
Hurricane Wind Scale. Some fluctuations in intensity are expected during the next couple of days, but Sam is forecast to remain a major hurricane through late this week.

Hurricane-force winds extend outward up to 65 kilometers from the center and tropical-storm-force winds extend outward up to 205 kilometers. The minimum central pressure estimated from Air Force Hurricane Hunter aircraft observations is 949 millibars.

Hurricane Sam's latest information as of 11:00 AM Wednesday 29th September 2021. (National Hurricane Center)
Hurricane Sam’s latest information as of 11:00 AM Wednesday 29th September 2021. (National Hurricane Center)

Hurricane Sam’s Watches & Warnings

Hurricane Sam's Watches and Warnings as of 11:00 AM Wednesday 29th September 2021. (National Hurricane Center)
Hurricane Sam’s Watches and Warnings as of 11:00 AM Wednesday 29th September 2021. (National Hurricane Center)

There are no coastal watches or warnings in effect at this time.

Swells generated by Sam will impact the Lesser Antilles during the next several days. Swells are expected to reach Bermuda and the Bahamas in the next day or so, and then spread to the United States east coast by this weekend. These swells could cause life-threatening surf and rip current conditions. Please consult products from your local weather office.

Swells have been affecting Trinidad and Tobago’s northern and eastern coastlines, causing choppy seas in nearshore areas.

Hurricane Sam's probabilities for tropical-storm-force winds as of 11:00 AM Wednesday 29th September 2021. (National Hurricane Center)
Hurricane Sam’s probabilities for tropical-storm-force winds as of 11:00 AM Wednesday 29th September 2021. (National Hurricane Center)

This system is of no direct threat to Trinidad and Tobago.

Hurricane Sam’s Forecast Discussion

Hurricane Sam (Weathernerds.org)

Sam has a well-organized cloud pattern on satellite imagery, with a 90 n mi-wide Central Dense Overcast surrounded by numerous convective banding features. Upper-level outflow has now become better established to the southeast of the hurricane. A NOAA Hurricane Hunter mission from a couple of hours ago reported a 20 n mi-wide diameter circular eye. The current intensity is held at 115 kt for this advisory, which is a little higher than the maximum winds observed in the earlier aircraft mission. However, since the estimated minimum central pressure of 949 is a little lower than it was earlier this morning and Sam’s intensity has been fluctuating, it is considered prudent not to lower the winds at this time. An Air Force Hurricane Hunter aircraft is scheduled to investigate the hurricane soon and will provide another intensity estimate.

Sam continues its slow northwestward trek with the current motion remaining near 310/8 kt. Sam should move northwestward and then northward around the western portion of the subtropical ridge over the eastern Atlantic during the next few days, and turn toward the north-northeast and northeast later in the forecast period.
The track guidance models are in very good agreement through 72 hours or so, with some increase in model spread thereafter. This increase in spread is largely due to how Sam will interact with a strong mid-latitude trough moving through Atlantic Canada. Some of the guidance suggests that this trough could partially bypass the hurricane around the end of the period and beyond, but this is not yet clear. The current NHC forecast track is not much different from the previous one and is in good agreement with the dynamical model consensus, TVCA.

The hurricane will continue to move over warm waters and in an environment of low vertical shear and diffluent upper-level flow for the next 1-2 days. Thus, it would not be surprising to soon see some restrengthening. The official intensity forecast is essentially a blend of the latest Decay-SHIPS and LGEM predictions, and is very similar to the previous NHC forecast. Sam is likely to remain a major hurricane into this weekend.

Key Messages:

  1. Large swells generated by Sam are affecting the Leeward Islands and will spread to portions of the Virgin Islands, Puerto Rico, Hispaniola, the Bahamas, and Bermuda by Thursday or Friday. Significant swells will likely reach the east coast of the United States and Atlantic Canada by the weekend. These swells will likely cause life-threatening surf and rip current conditions, and beachgoers and other interests along these coasts are urged to follow the advice of lifeguards and local officials through the upcoming weekend.

Tropical Cyclone Climatology

2021 has already produced 20 tropical cyclones in the Atlantic Basin, with the next system being named Victor for the 2021 Atlantic Hurricane Season. For this time of year, most systems form in the Caribbean, the Gulf of Mexico, and off of the Eastern United States.

As we head through the last few days of September and into October, we’ll continue to monitor the entire Atlantic closely as tropical cyclones could form from tropical waves, non-tropical low-pressure systems in the North Atlantic, and from the Central America Gyre in the Western Caribbean Sea or the southwestern Gulf of Mexico.

Facebook Comments