FLORIDA
STORMS
Tropical Depression Peter
LOCATED
160 MI NNE OF SAN JUAN PUERTO RICO
WINDS
35 MPH
PRESSURE
1009 MB
MOVING
WNW AT 8 MPH
From the National Hurricane Center at 500 PM AST Tue Sep 21 2021
Peter now a tropical depression.
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Alerts
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DISCUSSION

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

1. Rainfall around the southern periphery of Peter may lead to areas of urban and small stream flooding through early Wednesday across northern Hispaniola, Puerto Rico, and portions of the Virgin Islands.

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

1. Rainfall around the southern periphery of Peter may lead to areas of urban and small stream flooding through early Wednesday across northern Hispaniola, Puerto Rico, and portions of the Virgin Islands.

There are no coastal watches or warnings in effect.

There are no coastal watches or warnings in effect.

RAINFALL: Rainfall around the southern periphery of Tropical Depression Peter could produce additional rainfall totals of 1 to 4 inches, with storm total accumulations up to 6 inches, across portions of the Northern Leeward Islands, including portions of the Virgin Islands, as well as Puerto Rico and the northern portions of Hispaniola through Thursday morning. 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 this evening 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 Depression Peter could produce additional rainfall totals of 1 to 4 inches, with storm total accumulations up to 6 inches, across portions of the Northern Leeward Islands, including portions of the Virgin Islands, as well as Puerto Rico and the northern portions of Hispaniola through Thursday morning. 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 this evening 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 500 PM AST (2100 UTC), the center of Tropical Depression Peter was located near latitude 20.5 North, longitude 65.0 West. The depression is moving toward the west northwest near 8 mph (13 km/h). A turn to the north with a decrease in forward speed is expected beginning tomorrow. On the forecast track, the center of Peter will remain well north of the Virgin Islands and Puerto Rico tonight and should move well east of the southeastern Bahamas during the next few days. Maximum sustained winds have decreased to near 35 mph (55 km/h) with higher gusts. Additional gradual weakening is forecast over the next several days, and Peter could degenerate into a remnant low by Thursday. The estimated minimum central pressure is 1009 mb (29.80 inches).

At 500 PM AST (2100 UTC), the center of Tropical Depression Peter was located near latitude 20.5 North, longitude 65.0 West. The depression is moving toward the west northwest near 8 mph (13 km/h). A turn to the north with a decrease in forward speed is expected beginning tomorrow. On the forecast track, the center of Peter will remain well north of the Virgin Islands and Puerto Rico tonight and should move well east of the southeastern Bahamas during the next few days. Maximum sustained winds have decreased to near 35 mph (55 km/h) with higher gusts. Additional gradual weakening is forecast over the next several days, and Peter could degenerate into a remnant low by Thursday. The estimated minimum central pressure is 1009 mb (29.80 inches).

Like clockwork compared to prior days, deep convection has reignited closer to the increasingly elongated low-level circulation of Peter. Despite this increase in convective coverage, there does not appear to be much if any organization to this activity, with the upper-level cirrus taking on the appearance of a shapeless blob. In addition, an earlier 1157 UTC ASCAT-A pass received just after the prior advisory showed a peak wind retrieval of only 29 kt, well to the north of the low-level circulation. Furthermore, NOAA buoy 41043, located north of the center of Peter, has been observing peak 1-minute sustained winds between 20-25 kt over the last 6 hours. These lower winds, in combination with the lack of tropical storm force winds observed by the earlier Air Force Reserve Reconnaissance mission provide enough justification to downgrade Peter to a tropical depression this advisory with maximum sustained winds of 30 kt.

The ongoing afternoon convection appears to have slowed down the forward motion of Peter a bit this afternoon, but the heading remains off to the west-northwest at 300/7 kt. Peter is still expected to gradually move to the west-northwest in the short term, followed by a somewhat sharp turn to the north and north-northeast as a weakness in the low-level flow develops from a deep-layer trough positioned near Bermuda. Similar to this morning, the guidance is in general agreement on this solution, with some cross- and along-track spread. The latest NHC track forecast is just a bit more right compared to the previous advisory, leaning a bit closer to the consensus aids which have also shifted a bit right this advisory.

Peter's convective activity is unlikely to help improve the increasingly elongated vortex, mainly because the convection is likely to entrain dry mid-level air that often results in cool downdrafts disrupting the low-level cyclonic circulation more than helping. With deep-layer shear between 25-35 kt expected to persist for the next 36 hours in both the GFS- and ECMWF-SHIPS guidance, gradual weakening is likely to continue. By 36 hours, while intermittent bursts of deep convection will remain possible over warm sea-surface temperatures, both the GFS and ECMWF forecast simulated IR brightness temperatures show the convection becoming increasingly disorganized and unlikely to sustain Peter's status as a tropical cyclone. Thus, the cyclone is now forecast to become a remnant low in 36 hours. However, given that Peter's circulation is becoming increasingly elongated, it is also possible the system may open up into a trough even before this time period.

The last visible satellite images of Peter this evening indicated that its low-level center was losing definition and becoming even more elongated. Earlier, new bursts of convection associated with Peter had become oriented along a northeast to southwest axis, a possible sign that Peter may no longer have a well-defined center and could be opening up into a trough. But the estimated center position is now obscured by convective debris, and without recent scatterometer data to prove otherwise, Peter is maintained as a sheared tropical depression for this advisory. The initial intensity of 30 kt is consistent with a UW-CIMSS ADT objective 30-kt estimate and a T2.0/30 kt Dvorak classification from SAB.

It is estimated that Peter is moving northwestward, or 310/6 kt, although this is somewhat uncertain given the degraded low-level structure of the cyclone. The track reasoning remains consistent with previous advisories. Peter is forecast to turn more northward on Wednesday, and then move north-northeastward to northeastward through the end of the week as a trough to the north and northeast of Peter erodes the southern portion of the low-level steering ridge. The track consensus aids have shifted slightly to the right this cycle, and so the latest NHC track forecast has been adjusted a little to the right of the previous one.

Environmental conditions are expected to remain hostile for Peter over the next couple of days. Strong vertical wind shear of 25-30 kt will persist for the next 24-36 h, and GFS and ECMWF model simulated satellite imagery suggest that Peter will be unable to sustain enough deep, organized convection to maintain its status as a tropical cyclone for much longer. Thus, the NHC forecast shows Peter becoming a remnant low in 36 h, with some additional weakening expected before dissipation by this weekend. Of course, without sufficient convection to sustain the low-level vortex, it would not be surprising if the depression degenerated into a trough even sooner than forecast.

Like clockwork compared to prior days, deep convection has reignited closer to the increasingly elongated low-level circulation of Peter. Despite this increase in convective coverage, there does not appear to be much if any organization to this activity, with the upper-level cirrus taking on the appearance of a shapeless blob. In addition, an earlier 1157 UTC ASCAT-A pass received just after the prior advisory showed a peak wind retrieval of only 29 kt, well to the north of the low-level circulation. Furthermore, NOAA buoy 41043, located north of the center of Peter, has been observing peak 1-minute sustained winds between 20-25 kt over the last 6 hours. These lower winds, in combination with the lack of tropical storm force winds observed by the earlier Air Force Reserve Reconnaissance mission provide enough justification to downgrade Peter to a tropical depression this advisory with maximum sustained winds of 30 kt.

The ongoing afternoon convection appears to have slowed down the forward motion of Peter a bit this afternoon, but the heading remains off to the west-northwest at 300/7 kt. Peter is still expected to gradually move to the west-northwest in the short term, followed by a somewhat sharp turn to the north and north-northeast as a weakness in the low-level flow develops from a deep-layer trough positioned near Bermuda. Similar to this morning, the guidance is in general agreement on this solution, with some cross- and along-track spread. The latest NHC track forecast is just a bit more right compared to the previous advisory, leaning a bit closer to the consensus aids which have also shifted a bit right this advisory.

Peter's convective activity is unlikely to help improve the increasingly elongated vortex, mainly because the convection is likely to entrain dry mid-level air that often results in cool downdrafts disrupting the low-level cyclonic circulation more than helping. With deep-layer shear between 25-35 kt expected to persist for the next 36 hours in both the GFS- and ECMWF-SHIPS guidance, gradual weakening is likely to continue. By 36 hours, while intermittent bursts of deep convection will remain possible over warm sea-surface temperatures, both the GFS and ECMWF forecast simulated IR brightness temperatures show the convection becoming increasingly disorganized and unlikely to sustain Peter's status as a tropical cyclone. Thus, the cyclone is now forecast to become a remnant low in 36 hours. However, given that Peter's circulation is becoming increasingly elongated, it is also possible the system may open up into a trough even before this time period.

The last visible satellite images of Peter this evening indicated that its low-level center was losing definition and becoming even more elongated. Earlier, new bursts of convection associated with Peter had become oriented along a northeast to southwest axis, a possible sign that Peter may no longer have a well-defined center and could be opening up into a trough. But the estimated center position is now obscured by convective debris, and without recent scatterometer data to prove otherwise, Peter is maintained as a sheared tropical depression for this advisory. The initial intensity of 30 kt is consistent with a UW-CIMSS ADT objective 30-kt estimate and a T2.0/30 kt Dvorak classification from SAB.

It is estimated that Peter is moving northwestward, or 310/6 kt, although this is somewhat uncertain given the degraded low-level structure of the cyclone. The track reasoning remains consistent with previous advisories. Peter is forecast to turn more northward on Wednesday, and then move north-northeastward to northeastward through the end of the week as a trough to the north and northeast of Peter erodes the southern portion of the low-level steering ridge. The track consensus aids have shifted slightly to the right this cycle, and so the latest NHC track forecast has been adjusted a little to the right of the previous one.

Environmental conditions are expected to remain hostile for Peter over the next couple of days. Strong vertical wind shear of 25-30 kt will persist for the next 24-36 h, and GFS and ECMWF model simulated satellite imagery suggest that Peter will be unable to sustain enough deep, organized convection to maintain its status as a tropical cyclone for much longer. Thus, the NHC forecast shows Peter becoming a remnant low in 36 h, with some additional weakening expected before dissipation by this weekend. Of course, without sufficient convection to sustain the low-level vortex, it would not be surprising if the depression degenerated into a trough even sooner than forecast.

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