Small town USA guy. Politics nerd. Soccer fan. Interested in eyewalls, deformation zones, and hook echos.
By: TropicalAnalystwx13 , 4:29 AM GMT on September 28, 2012
Nadine, the never-ending tropical cyclone of the 2012 Atlantic hurricane season, continues to spin harmlessly over the waters of the Northeast Atlantic Ocean this evening. As of the latest public advisory from the National Hurricane Center, the cyclone was located within 20 nautical miles of 28.8N 33.6W, or about 740 miles south-southwest of the Azores. Maximum sustained winds and the minimum barometric pressure were steady at 65 mph and 993 millibars, respectively, and Nadine was moving towards the west at 7 mph. Nighttime infrared imagery reveals that Nadine is, for the first time in over a week, a well-formed tropical cyclone, with deep convection atop the low-level center and excellent upper-level outflow towards the southwest.
Figure 1. Infrared imagery of Tropical Storm Nadine over the Northeast Atlantic.
The forecast for Nadine
The forecast for Nadine...as it has for the past two weeks...remains very complicated, in terms of both track and intensity. The cyclone is currently situated south of an east-to-west oriented ridge of high pressure, which has been responsible for the due westward motion over the past 12 to 18 hours. Nadine is forecast to soon round the southwest periphery of this ridge and curve towards the north as it feels the effects of an approaching shortwave trough over the North Atlantic. Models are in good agreement that this weakness will cause a continued north-northwest motion through 72 to 96 hours out before it is deja-vu all over again. As this shortwave trough exits to the northeast of Nadine, the storm is expected to slow down, and potentially stall, while embedded within a region of weak steering currents. This is depicted in the official National Hurricane Center track forecast for the day 4 and 5 points.
The environment over the next 12 to 24 hours is marginally conducive for slight intensification of the storm. Sea Surface Temperatures remain steady near 26 °C and wind shear is roughly 20 knots. As Nadine curves towards the north-northwest, it is expected to enter sub-26 °C ocean temperatures, and wind shear may increase to close to 30 knots between 36 hours and 48 hours out. However...depending on the storm's proximity to the shortwave trough to the north, the effects of this otherwise destructive wind shear may be minimized. Wind shear may lower again after 48 hours out, but Sea Surface Temperatures are expected to remain below the threshold needed to sustain a tropical cyclone, so slow...emphasis on slow...weakening is expected.
...MAXIMUM SUSTAINED WINDS FORECAST...
INIT 29/0300Z 55 KT 65 MPH
12H 29/1200Z 60 KT 70 MPH
24H 30/0000Z 60 KT 70 MPH
36H 30/1200Z 55 KT 65 MPH
48H 01/0000Z 55 KT 65 MPH
72H 02/0000Z 55 KT 65 MPH
96H 03/0000Z 55 KT 65 MPH
120H 04/0000Z 50 KT 60 MPH
Miriam no more
Miriam is no longer a tropical cyclone this evening, succumbing to the effects of a dry, stable air mass, and Sea Surface Temperatures cooler than 24 °C. The remnant circulation of the system is expected to drift towards the south thanks to a ridge of high pressure to its north, and is not a threat to any landmasses.
Figure 2. Shortwave imagery of Post-Tropical Cyclone Miriam west of Baja California.
94E unlikely to develop
A broad area of low pressure, dubbed Invest 94E by the National Hurricane Center, is unlikely to develop into a tropical cyclone prior to moving into the coastline of Mexico over the weekend. While deep convection is prevalent atop the low-level circulation, the low itself is not well-defined nor closed. Environmental conditions are becoming less favorable for development and the National Hurricane Center has lowered their percentage for tropical cyclone development for the storm down to 50%. Regardless of development, however, heavy rainfall, gusty winds, and rip currents are likely to affect the coastline of Mexico throughout the weekend.
Figure 3. Shortwave imagery of Invest 94E south of the coastline of Mexico.
The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.
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