1. Rainfall around the southern periphery of Tropical Storm Peter may lead to areas of urban and small stream flooding from late today into Tuesday across 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.

RAINFALL: The outer bands south of the tropical storm 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 late today through Tuesday. This rainfall may lead to areas of urban and small stream flooding.

SURF: Swells generated by Tropical Storm Peter are expected to reach the northern Leeward Islands tonight and Monday. These swells could cause life threatening surf and rip current conditions. Please consult products from your local weather office.

At 1100 AM AST (1500 UTC), the center of Tropical Storm Peter was located near latitude 17.6 North, longitude 56.5 West. Peter is moving toward the west northwest near 17 mph (28 km/h), and this general motion along with a gradual decrease in forward speed is is expected through Tuesday. A turn to the northwest is expected to occur by Wednesday. On the forecast track, the center of Peter is expected to pass well north of the Leeward Islands on Monday and Tuesday. Based on data from a Air Force Reserve Hurricane Hunter aircraft, maximum sustained winds remain near 45 mph (75 km/h) with higher gusts. Little change in strength is forecast through today. Some slight weakening is expected tonight into Monday. Tropical storm force winds extend outward up to 115 miles (185 km), primarily northeast of the center. The estimated minimum central pressure based on the aircraft data is 1007 mb (29.74 inches).

Earlier this morning, Peter began to encounter increasing southwesterly shear emanating from flow around an upper-level trough to its northwest. This shear caused the low-level center of the storm to separate from the deep convection and as of now is located over 100 n mi from the edge of that band of convection. An Air Force Reserve Hurricane Hunter aircraft has been investigating the cyclone for the past few hours and has provided helpful data on the structure and intensity of Peter. Based on the aircraft data, tropical-storm-force winds extend at least 100 n mi to the northeast of the center, while there are no tropical-storm-force winds in the southern semicircle. The initial intensity of 40 kt is based on aircraft passes through the northeastern quadrant that measured peak 925 mb flight-level winds of 56 and 54 kt.

The initial motion is 290/15 kt. Peter is forecast to continue to move in this west-northwestward direction for the next couple of days as it is steered to the south of a subtropical ridge. This ridge is expected to weaken in a few days which should cause the cyclone to turn northwestward. Late in the forecast period a turn to the north and possibly northeast is expected to occur as Peter gets caught in the flow around a large trough to its north. As mentioned in the special advisory discussion a couple hours ago, a shift to the west-southwest of the track was required to accommodate a initial position adjustment. Some additional southward adjustments were made to the official NHC track for this advisory to come into better agreement with a blend of the GFS/ECMWF solutions that also indicate a shallower system.

The UW-CIMSS shear analysis suggests about 20 kt of southwesterly shear is impacting Peter. Just to its west and northwest, where the cyclone is heading, the shear is analyzed as 30 kt or greater. Given that Peter is already exhibiting the structure of a highly sheared tropical cyclone, some slight weakening is now forecast tonight into tomorrow. There is quite a bit of spread in the environmental forecast between the GFS and ECMWF beyond day 3, as the GFS shows shear increasing to 40 kt, while the ECMWF indicates a less hostile environment with 20 kt of shear. Assuming Peter survives its interaction with the upper trough to its northwest over the next few days, additional weakening is indicated due to the ongoing shear. It should be noted that quite a few GFS ensemble members open Peter into a trough by the end of the forecast period. The latest NHC intensity forecast is near the various consensus solutions. However, due to the possibility the cyclone may not survive the next few days, the confidence in this forecast is lower than normal.

Based on the track, intensity, and wind radii forecast, no tropical storm watches or warnings are required for the northern Leeward Islands, Virgin Islands or Puerto Rico. However, interests there should monitor the progress of the system as locally heavy rain is possible on Monday and Tuesday when it is expected to pass to the north of the area.