Ed Dunham
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| (Former Meteorologist & CFHC Forum Moderator (Ed Passed Away on May 14, 2017)) |
| Mon Jun 14 2010 05:04 AM |
Low Latitude Tropical Cyclones
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A central Atlantic tropical cyclone in June is a rare event but Invest 92L seems destined to develop into one. Clark has pointed out how unusual it is for a tropical cyclone to develop in the middle of the basin in June at such a far eastern and far southern location. I examined all of the seasons since the start of the satellite era in 1964 to see just how often a tropical cyclone forms at a latitude of 10 degrees North or less in any month. The historical record was limited to only those storms that eventually became at least a tropical storm.
Those 46 seasons produced 494 tropical storms/hurricanes and subtropical storms with 18 Tropical Depressions forming at a latitude below 10 degrees (3.6% of the total number of storms). Four of the 18 became a tropical storm at or below 10 degrees North latitude. In 1990, Fran became a tropical storm at 9.0N 53.6W. Also in 1990, Isidore became a tropical depression at 7.2N 23.4W and a tropical storm at 10.0N 32.7W. In 2002, Dolly became a tropical storm at 9.7N 32.2W and in 2004, Ivan became a tropical storm at 9.7N 35.0W. Ivan was unique in that it dipped south of due west and became a 50 knot TS at 8.9N 36.5W, a hurricane at 9.5N 43.0W and reached a sustained wind of 115 knots at 10.6N 48.5W. Joan (1988) gets honorable mention with TS status at 10.1N 45.0W.
Invest 92L has a chance to join this short list if it should attain TD status while still below 10 degrees in latitude.
ED
| cieldumort |
| (Moderator) |
| Mon Jun 14 2010 07:06 AM |
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Re: Low Latitude Tropical Cyclones
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Context is everything, and the more intensely I review records going back even just a few short years ago, the less faith I have in the historical records. Nonetheless, a bona fide early season tropical cyclone formation south of 10N.. east of 50W still has to be quite a feat, especially, especially this early in a season, however imperfect the records may be.
Having said that, it looks as if 92L may be trying to recenter its LLC more closely aligned with the deepest convection tonight, which has been existing to the north of the old center. A similar event taking place last overnight appeared to help cause the entire feature to temporarily shift track a little more to the northwest, than wnw or w.
In some regards, 92L is tonight reminding me of pre-Hurricane Humberto (2007). With its persistent, healthy surface low encountering some exceptionally low shear and within very favorable TPW, while over fully supportive SSTs - I do see a real chance for fairly rapid development up until 92L bumps into the shear monster still at least a day or two away.
The largest inhibiting factors until that encounter would be its size, followed closely by its closeness to the equator.
As for position, if re-centering concludes, my best guess puts the coc now closer to 9N 38.5W as of 6 UTC.
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Ed Dunham
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| (Former Meteorologist & CFHC Forum Moderator (Ed Passed Away on May 14, 2017)) |
| Mon Jun 14 2010 02:48 PM |
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Re: Low Latitude Tropical Cyclones
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Invest 92L continues to consolidate but additional organization near the center is still required before the system can reach TD strength. Approximate satellite position estimate puts the center near 10.2N 40.8W at 14/14Z. Movement is now more to the west northwest rather than northwest - at about 18 knots.
ED