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000
WTNT41 KNHC 250254
TCDAT1

TROPICAL STORM OTTO DISCUSSION NUMBER 17
NWS NATIONAL HURRICANE CENTER MIAMI FL AL162016
900 PM CST THU NOV 24 2016

Radar data from Las Nubes, Nicaragua, indicate that the core of Otto has remained well organized since landfall, with an eye still discernible. On the other hand, the convective clouds associated with the cyclone have warmed considerably since landfall. There have been no surface observations from the core, so the initial intensity is reduced to a somewhat uncertain 60 kt based on the decay in the satellite appearance.

The initial motion estimate is 265/11. Otto is located over northwestern Costa Rica and should emerge into the Pacific during the next few hours. Easterly steering flow on the south side of a deep-layer ridge located over the northwestern Caribbean Sea and southern Mexico is expected to keep Otto moving in a westward to west-southwestward direction for the next 72 hours or so. After that time, the cyclone or its remnants are expected to reach the end of the ridge and turn northwestward. The new forecast track is similar to the previous track through 72 hours, then is shifted a little to the left of the track based on a shift in the consensus models.

During the first 36 hours over the Pacific, Otto is likely to be over warm sea surface temperatures in an environment of moderate to strong easterly vertical wind shear. The intensity forecast during this time will show a slow weakening in agreement with the previous forecast due to the uncertainties in the strength of the shear. However, given the level of organization it would not be surprising if some intensification occurred. Around 48 hours, the cyclone is likely to encounter cooler sea surface temperatures which should cause a faster weakening. From 72-120 hours, Otto is expected to move over warmer water with decreasing shear at the same time it encounters a much drier air mass. The intensity forecast uses the premise that the dry air will cause the system to decay and thus calls for Otto to be a remnant low by 120 hours. It should be noted, though, the the intensity forecast after 48 hours remains near the lower edge of the guidance.

The primary threat from Otto will continue to be torrential rainfall, which will result in dangerous flooding and mudslides.

Since Otto has maintained itself as a tropical cyclone all the way across the land mass of Central America, based on National Weather Service and World Meteorological Organization protocols, it will retain the name Otto when it moves over the eastern Pacific in a few hours. Product headers will change to eastern Pacific headers beginning with the next complete advisory at 0900 UTC. The intermediate advisory at 0600 UTC will be issued under an Atlantic header. The ATCF identifier will change from AL162016 to EP222016 at 0900 UTC.



FORECAST POSITIONS AND MAX WINDS

INIT 25/0300Z 10.9N 85.6W 60 KT 70 MPH...INLAND 12H 25/1200Z 10.5N 87.4W 55 KT 65 MPH...OVER THE PACIFIC 24H 26/0000Z 10.0N 90.0W 55 KT 65 MPH 36H 26/1200Z 9.6N 93.0W 50 KT 60 MPH 48H 27/0000Z 9.4N 96.0W 45 KT 50 MPH 72H 28/0000Z 9.5N 102.0W 45 KT 50 MPH 96H 29/0000Z 11.0N 105.0W 40 KT 45 MPH 120H 30/0000Z 13.0N 106.0W 30 KT 35 MPH...POST-TROP/REMNT LOW

$$ Forecaster Beven

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