After a lull of about 20 days, a new subtropical depression has developed to the north of Puerto Rico. The system consists of a well-defined curved band to the north of the system, but convection is limited to non-existent over and to the south and east of the center.
Visible satellite image of 07L
STD 07L is forecast to move northward and intensify into a weak tropical storm, before getting abosorbed into a frontal system.
The 2014 Atlantic hurricane season has finally gotten into business. Tropical depression One has developed out of a low pressure area (formerly 91L), which has been meandering of the northeastern coast of Florida during the past few days.
Current satellite imagery (as of 07:30 UTC) shows that Tropical depression One is under impact of significant northerly shear, which is blowing the convection southward away from the LLCC (low level circulation centre). In fact, the LLCC is still partially exposed (according to CIMSS).
Visible satellite loop of Tropical depression 01 (Courtesy: NHC)
Despite the seemingly disorganized appearance, the NHC forecasts gradual strengthening of the cyclone, reaching a peak intensity of 60 kt near the Eastern Seaboard. This is caused by a trough which forces the cyclone to recurve toward the northeast after a slow southwestward drift in a few days. The forecast track from the NHC can be seen below:
Forecast track of Tropical depression 1.
With the arrival of the new year, the 2013 Atlantic hurricane season has come to an end. Therefore, it's time take a look back to this
hurricane season and the storms that developed in this period in the Atlantic.
The Atlantic hurricane season was off a quick start. The first storm, Andea, developed at the fifth of June. The storm was a short-lived one, though. The system impacted Florida and the eastern coast of the US when it moved generally northeastward during its lifetime.
The second storm of the season, Barry, developed on the 15th of June. The system was one of the 4 storms which impacted Mexico, the others being Ingrid, Fernand and TD Eight. The system was always close to land during its lifetime, which was the main controlling factor of its intensity.
Chantal was another short-lived storm, which developed on July 7. The system moved generally westward during its lifetime. It developed to the east of the Carribean and found its demise in central Carribean. Chantal is noted for having a very rapid forward speed during its lifetime, with speeds up to 55 km/h being measured. This hampered the organization of the cyclone significantly.
Satellite image of Chantal (from NASA)
Dorian was a storm that developed on 23 July just to the west of Africa, where it became a tropical storm. The system was short-lived, though it had 2 lives, as it regenerated just to the east of Florida. It never made it past TD status at that point, due to high shear values present in that area.
Erin continued the theme of the Atlantic hurricane season to produce short-lived tropical storms. Erin developed on the 15th of August to the west of Africa. The system was surrounded by vast areas of dry Saharan air, and dissipated 3 days after its development due to this dry air.
Fernand was one of the 4 cyclones to hit Mexico during the season. It developed unexpectedly on the 25th of August. The system was located in the southeastern extreme of the Gulf of Mexico. Because the system moved westward fairy quickly, it reached land in a hurry and dissipated soon therafter.
Gabrielle developed on the 26th of August. The system moved generally northward during its short lifetime, and it impacted Bermuda on its track. Moreover, Haiti and Puerto Rico were hit by the tropical wave that spawned Gabrielle.
There was also one tropical depression that never reached hurricane status. The system developed on the 6th of December. It was one of the 4 storms to impact Mexico.
Humberto was the first hurricane to develop in the 2014 Atlantic hurricane season. It was also the strongest cyclone of the season, with peak winds of only 150 km/h (!). Humberto also had 2 lives, redeveloping for a short while in the Central Atlantic. It impacted the Cape Verde islands as a tropical storm.
What was interesting about Humberto was that it was almost the latest hurricane formation on record. It was just in time to prevent the season from attaining this dubious record.
Ingrid also became a hurricane, developing on the 21th of September. The cyclone stayed in the Gulf of Mexico during most of its lifetime, and made landfall in Mexico as a borderline hurricane/TS.
Of note is that Ingrid, along with Manuel from the Eastern Pacific, created a disastrous rain event over Mexico itself, resulting in many deaths. A visible satellite image of the event can be seen below:
Jerry was another tropical storm that didn't last for long. The system developed on September 29 in the Central Atlantic. It moved northeastward without ever impacting land.
Karen was a tropical storm that summarized the Atlantic hurricane season in just one go. The cyclone developed on October 3 near the Yucatan Penninsula. It moved north-norhtwestward toward the US coast during its lifetime. The NOAA forecasted the system would reach the US coast near New Orleans as a 55-60 kt tropical storm. However, strong wind shear and very dry air prevented the system from reaching the coast as a tropical storm, and it dissipated a few hundred miles to the south of New Orleans.
Lorenzo was once again a short-lived tropical storm that developed in the Central Atlantic on the 21st of October. The system moved eastward during its lifetime, dissipating without further notice.
The final named storm of the season was Melissa. The storm developed in the Central Atlantic during the 18th of November. At the beginning, the system was classified as a subtropical storm while moving slowly northward. Later on, the storm turned into a fully-tropical storm, when its track bended more and more toward the east. The system turned extratropical soon thereafter due to cooler waters and interaction with the midlatitudes.
For me, Melissa was a very interesting tropical storm. This was because models were split in two camps regarding the final outcome of the extratropical remnants of Melissa. Some models moved it east-southeastward, while others recurved it back toward the North. This difference resulted in different weather patterns over northwestern Europe. A track to the north would result in a block to form over Europe due to Warm Air Advection, resulting in cold, dry weather. A track more to the east of Melissa would cause more of a zonal pattern, with a low pressure dominated type of weather. Ultimately, it appeared that the last possibility was also the correct one.
Unnamed subtropical storm
There was also one unnamed subtropical storm which developed just outside the boundaries of the Atlantic hurricane season. It developed at the fifth of December near the Azores. From there, it moved slowly northward until dissipation.
Below is a track history of all hurricanes and tropical storms of the 2013 Atlantic hurricane season, as from NASA:
Statistics about the hurricane season
The Atlantic hurricane season produced 15 tropical cyclones, of which only 2 attained hurricane status. Of those, none acquired Major hurricane status, which ties with the record of the least major hurricanes developing during a Atlantic hurricane season.
The total ACE value of the season was 30, while the average in the Atlantic basin is 93.2. The ACE is a measure for the intensity, frequency and lifetime of tropical systems. The values above give that this hurricane season had an ACE of only 32% of average.
Pre-seasonal forecasts all argued for a pretty active hurricane season. Given what we know by now, they have been far off the mark. Below is a summary of how Philip Klotzbach and William Gray (two renowned long-range hurricane forecasters) look back to this hurricane season:
The complete article (very interesting, though rather extensive) can be found below:
Another nice, shorter summary can be found in the link below:
Thanks all for contributing to this hurricane season! I'm looking forward to a 2014 Atlantic hurricane season full of excitement!
BTW: Additions or remarks are always welcome!
An unnamed subtropical storm appears to have developed just after the official end of the Atlantic hurricane season. Post-season analysis from NOAA indicates that this subtropical storm developed on the 5th of December just to the south of the
Azores. The system didn't live for very long, though, as it lasted only for 2 days.
The system could first be recognized on the 29th of November. This can be seen in the GFS chart below:
GFS 29 November pressure analysis
The precursor of the unnamed subtropical storm can be seen as the sub-1010 hPa trough (at the surface) at the extreme southwestern part of the map. Note that there is also a weak 500 hPa trough associated with the low (as indicated by the lighter orange colors surrounded by darker orange colors).
On the second of December, the low has deepened somewhat:
GFS 2 December pressure analysis
The precursor low pressure area can now be seen just to the south of the Azores as a sub-1005 hPa low. Note that the 500 hPa trough associated with the surface low has attained a connection with the parent trough far to the north of the system.
At the 4th of December, the low has attained subtropical cyclone status. Moreover, the system has attained its minimum surface level pressure by then:
GFS 4 december pressure analysis
The storm has reached a pressure of less than 1000 mb in this chart. The 500 hPa trough has once again become disconnected from the parent trough to its north, and therefore, it can be considered a cut-off low.
Consequences for the 2013 Atlantic hurricane season
As a result, the total storm count has been upped to 14, indicating a slightly above-median activity in this basin. However, as mentioned previously on other parts of this forum, the hurricane and major hurricane count were well below normal, with only two storms attaining hurricane intensity and none of them reaching major hurricane intensity.
It is interesting to note, though, that even in the Satellite era, storms can still go unnoticed by experts as well.
The full synoptic history and meteorological background can be found in the link below:
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