FLORIDA
STORMS
Tropical Storm Peter
LOCATED
110 MI N OF THE NORTHERN LEEWARD ISLANDS
WINDS
50 MPH
PRESSURE
1008 MB
MOVING
WNW AT 12 MPH
From the National Hurricane Center at 1100 PM AST Mon Sep 20 2021
Resilient Peter maintains its strength despite strong shear.
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Alerts
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DISCUSSION

1. Rainfall around the southern periphery of Tropical Storm Peter may lead to areas of urban and small stream flooding through Tuesday across northern Hispaniola, Puerto Rico, the Virgin Islands, and the Northern Leeward Islands.

1. Rainfall around the southern periphery of Tropical Storm Peter may lead to areas of urban and small stream flooding through Tuesday across northern Hispaniola, Puerto Rico, the Virgin Islands, and the Northern Leeward Islands.

There are no coastal watches or warnings in effect. Interests in the northern Leeward Islands, Virgin Islands, and Puerto Rico should monitor the progress of this system.

There are no coastal watches or warnings in effect. Interests in the northern Leeward Islands, Virgin Islands, and Puerto Rico should monitor the progress of this system.

RAINFALL: Rainfall around the southern periphery of Tropical Storm Peter could produce rainfall totals of 1 to 3 inches, with locally higher amounts possible, across portions of the Northern Leeward Islands, including the Virgin Islands, as well as Puerto Rico and the northern portions of Hispaniola through Tuesday. This rainfall may lead to areas of urban and small stream flooding.

SURF: Swells generated by Peter are affecting the northern Leeward Islands and Puerto Rico, and will continue spreading westward to Hispaniola on Tuesday and the Bahamas on Wednesday. These swells could cause life threatening surf and rip current conditions. Please consult products from your local weather office.

RAINFALL: Rainfall around the southern periphery of Tropical Storm Peter could produce rainfall totals of 1 to 3 inches, with locally higher amounts possible, across portions of the Northern Leeward Islands, including the Virgin Islands, as well as Puerto Rico and the northern portions of Hispaniola through Tuesday. This rainfall may lead to areas of urban and small stream flooding.

SURF: Swells generated by Peter are affecting the northern Leeward Islands and Puerto Rico, and will continue spreading westward to Hispaniola on Tuesday and the Bahamas on Wednesday. These swells could cause life threatening surf and rip current conditions. Please consult products from your local weather office.

At 1100 PM AST (0300 UTC), the center of Tropical Storm Peter was located near latitude 19.8 North, longitude 62.8 West. Peter is moving toward the west northwest near 12 mph (19 km/h). This general motion is expected to continue for the next day or so, followed by a turn to the northwest with a decrease in forward speed on Wednesday, and then a turn to the north by Wednesday night. On the forecast track, the center of Peter will pass north of the Virgin Islands and Puerto Rico on Tuesday. Recent satellite derived wind data indicate that maximum sustained winds remain near 50 mph (85 km/h) with higher gusts. Slow weakening is forecast during the next few days. Tropical storm force winds extend outward up to 175 miles (280 km) from the center, primarily in the northeastern quadrant. The estimated minimum central pressure is 1008 mb (29.77 inches).

At 1100 PM AST (0300 UTC), the center of Tropical Storm Peter was located near latitude 19.8 North, longitude 62.8 West. Peter is moving toward the west northwest near 12 mph (19 km/h). This general motion is expected to continue for the next day or so, followed by a turn to the northwest with a decrease in forward speed on Wednesday, and then a turn to the north by Wednesday night. On the forecast track, the center of Peter will pass north of the Virgin Islands and Puerto Rico on Tuesday. Recent satellite derived wind data indicate that maximum sustained winds remain near 50 mph (85 km/h) with higher gusts. Slow weakening is forecast during the next few days. Tropical storm force winds extend outward up to 175 miles (280 km) from the center, primarily in the northeastern quadrant. The estimated minimum central pressure is 1008 mb (29.77 inches).

Peter has proven to be a resilient tropical cyclone, despite strong upper-level wind shear that continues to displace its deep convection well east of its now exposed low-level center. Data from an Air Force Reserve Hurricane Hunter aircraft investigating Peter tonight, as well as recent scatterometer data, indicate that the cyclone has maintained its tropical storm intensity. An ASCAT-A pass shows several 40-kt wind vectors, with tropical-storm-force winds extending outward up to 150 n mi from the center in the northeastern quadrant. The aircraft has found peak 925-mb flight-level winds of 47 kt and SFMR winds of around 35 kt, although it did not sample the area where ASCAT depicted the strongest winds. The initial intensity is held at a possibly generous 45 kt for this advisory based on the scatterometer data.

An upper-level trough to the northwest of Peter should maintain 20 to 30 kt of vertical wind shear over the cyclone for the next 2-3 days. Thus, intensification seems unlikely during this period, despite 29 deg C SSTs along Peter's forecast track. If the tropical cyclone can endure these hostile upper-level winds, it could survive through the entire forecast period, although the drier mid-level environment at higher latitudes will also work against Peter later this week. However, an alternative scenario that has been favored by the GFS is that Peter weakens sooner due to a lack of sustained convection and opens up into a trough late this week. The long-range forecast is further complicated by the potential development of another non-tropical low to the north of Peter later this week, which could interact with or absorb Peter. The official NHC intensity forecast is similar to the previous one and only shows gradual weakening over the next several days, which is in good agreement with the HCCA and IVDR consensus aids.

Data from the aircraft indicate that the center has moved westward and slowed down a bit over the past several hours, and Peter's initial motion is estimated to be 285/10 kt. Peter is expected to continue moving generally west-northwestward through Tuesday, as it is steered around the southern extent of a low- to mid-level ridge over the central and western Atlantic. By Wednesday, a mid-level cutoff low is forecast to develop to the north of Peter over the western Atlantic, which will induce a weakness in the steering ridge. Therefore, the cyclone is forecast to slow down and turn northward and then north-northeastward through the latter part of the week and into the weekend. There are some larger along-track differences noted in the guidance at days 4-5, with the ECMWF moving or re-forming the center much farther north than the rest of the track guidance. The official NHC track forecast is shifted slightly to the right at 48 h and beyond, based on the latest TVCA and HCCA consensus aids. At longer ranges, the forecast is of much lower confidence and trends a bit slower than the consensus aids, which are heavily influenced by the outlying ECMWF solution.

Peter has proven to be a resilient tropical cyclone, despite strong upper-level wind shear that continues to displace its deep convection well east of its now exposed low-level center. Data from an Air Force Reserve Hurricane Hunter aircraft investigating Peter tonight, as well as recent scatterometer data, indicate that the cyclone has maintained its tropical storm intensity. An ASCAT-A pass shows several 40-kt wind vectors, with tropical-storm-force winds extending outward up to 150 n mi from the center in the northeastern quadrant. The aircraft has found peak 925-mb flight-level winds of 47 kt and SFMR winds of around 35 kt, although it did not sample the area where ASCAT depicted the strongest winds. The initial intensity is held at a possibly generous 45 kt for this advisory based on the scatterometer data.

An upper-level trough to the northwest of Peter should maintain 20 to 30 kt of vertical wind shear over the cyclone for the next 2-3 days. Thus, intensification seems unlikely during this period, despite 29 deg C SSTs along Peter's forecast track. If the tropical cyclone can endure these hostile upper-level winds, it could survive through the entire forecast period, although the drier mid-level environment at higher latitudes will also work against Peter later this week. However, an alternative scenario that has been favored by the GFS is that Peter weakens sooner due to a lack of sustained convection and opens up into a trough late this week. The long-range forecast is further complicated by the potential development of another non-tropical low to the north of Peter later this week, which could interact with or absorb Peter. The official NHC intensity forecast is similar to the previous one and only shows gradual weakening over the next several days, which is in good agreement with the HCCA and IVDR consensus aids.

Data from the aircraft indicate that the center has moved westward and slowed down a bit over the past several hours, and Peter's initial motion is estimated to be 285/10 kt. Peter is expected to continue moving generally west-northwestward through Tuesday, as it is steered around the southern extent of a low- to mid-level ridge over the central and western Atlantic. By Wednesday, a mid-level cutoff low is forecast to develop to the north of Peter over the western Atlantic, which will induce a weakness in the steering ridge. Therefore, the cyclone is forecast to slow down and turn northward and then north-northeastward through the latter part of the week and into the weekend. There are some larger along-track differences noted in the guidance at days 4-5, with the ECMWF moving or re-forming the center much farther north than the rest of the track guidance. The official NHC track forecast is shifted slightly to the right at 48 h and beyond, based on the latest TVCA and HCCA consensus aids. At longer ranges, the forecast is of much lower confidence and trends a bit slower than the consensus aids, which are heavily influenced by the outlying ECMWF solution.

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