Gabrielle Moves on, Active Tropics


Infrared Satellite Image of the North Atlantic showing the locations of Tropical Cyclones in the Atlantic including their forecast tracks as of 6pm Bermuda time in red. A cold front, steering the remnants of Gabrielle in blue. And a Tropical Wave in orange.
Infrared Satellite Image of the North Atlantic showing the locations of Tropical Cyclones in the Atlantic including their forecast tracks and current max sustained wind speed as of 6pm Bermuda time in red. A cold front, steering the remnants of Gabrielle in blue. And a Tropical Wave in orange.

The official three-day rainfall totals are in for Tropical Storm Gabrielle – 0.49″ (September 10th), 0.42″ (11th), and 0.52″ (12th) give a total of 1.43″ of rain from Tropical Storm Gabrielle at the Bermuda Weather Service. Some personal weather stations observed between 2-4″ of rain. This official figure is significantly lower than the 3-5″ with isolated totals near 7″ that the National Hurricane Center predicted just hours before Gabrielle’s closest approach.  This highlights one of the continuing weaknesses in Tropical Cyclone forecasting – intensity. Had Gabrielle maintained its convective structure on approach as forecast it would have brought stronger winds and rainfall totals comparable to that forecast. However, despite the mediocre intensity forecast, the track of Gabrielle was near perfect in the five day range. Intensity forecasting is still an area that the National Hurricane Center is working on as a part of their initiative to improve Tropical Cyclone forecasting. Meanwhile Tropical Storm Gabrielle has continued to the north and is now impacting Nova Scotia, Prince Edwards Island, and Newfoundland as a post-tropical cyclone bringing gusty winds and heavy rain.

Lance MODIS Aqua imagery of Hurricane Humberto near its peak intensity of 85mph and 986mb yesterday.
Lance MODIS Aqua imagery of Hurricane Humberto near its peak intensity of 85mph and 986mb yesterday. The Cape Verde Islands can be seen in the bottom right, along with some Saharan dust.

Hurricane Humberto in the far eastern Atlantic has moved north, away from the Cape Verde islands and into cooler waters. This has resulted in a significant reduction in deep convection over the storm and a subsequent weakening. Humberto is a Tropical Storm with 50mph winds as of the 6pm Bermuda Time advisory. Humberto is expected to begin a turn back towards the west tonight and move into warmer waters, potentially allowing some restrengthening before recurving through a weakness in the Bermuda-Azores ridge in the Central Atlantic in five days. Humberto is not a threat to Bermuda at this time and the current forecast does not suggest it will become a threat.

Tropical Storm Ingrid formed in the Bay of Campeche this morning, and as of the 6pm Bermuda Time advisory, Ingrid is moving very slowly if at all. This storm should eventually take a track towards the northwest into Mexico or southern Texas, spreading torrential rains that will likely lead to disastrous flash flooding and mud slides. The forecast track takes Ingrid over a region of Mexico that has been stuck under the monsoon trough for much of September so far. Tropical Storm Fernand, and Tropical Depression 8 have dumped heavy rains, and now Ingrid is set to add up to 25″ of rain in this mountainous region. Deep tropical moisture associated with the monsoon trough, and the warm waters of the Bay of Campeche are feeding Ingrid at the surface, and an expanding upper ridge is helping to ventilate and support convective growth aloft. Only proximity to land should hinder development of Ingrid as the storm slowly moves inland over the next three days or so, this could mean that Ingrid becomes the second Hurricane of the season – we will have to watch for that. Becoming a hurricane would provide a larger wind threat in addition to the potential for disastrous flooding in Mexico. Regardless, Ingrid is not a threat to Bermuda at this time.

Back to the Central Atlantic, an increase in convection along a persistent tropical wave northeast of the Lesser Antilles may need to be monitored for tropical development in the long term if convection begins to persist. There is a very low chance for this to develop, but it is in a steering setup that favors a track towards Bermuda should it develop.

We are now well into the climatological peak of Hurricane Season and it is not uncommon to have multiple tropical cyclones active at once in the Atlantic. As always, conditions can change quickly in the tropics so it is important to stay tuned to the latest official information on Atlantic and Eastern Pacific tropical cyclones by monitoring the National Hurricane Center‘s website. Official forecasts for Bermuda can be found at the Bermuda Weather Service, additional products, including warnings for Bermuda will be posed there.

The Joint Typhoon Warning Center's latest forecast track for Tropical Storm Man-yi.
The Joint Typhoon Warning Center’s latest forecast track for Tropical Storm Man-yi.

In the Western Pacific, Tropical Storm Man-yi is strengthening as it begins to make a turn to the north. Man-yi is expected to become a Typhoon over the weekend (JTWC) before making landfall in Japan. Man-yi is a large tropical cyclone set to bring gales to many of the larger more densely populated cities, including those in the Tokyo region, and should be monitored closely for any sudden changes in intensity or track. The Japan Meteorological Agency is also issuing advisories on Man-yi, but they use 10-minute sustained winds and so do not show Man-yi becoming a typhoon.

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