TROPICAL CYCLONE FORMATION: POST TROPICAL CYCLONE HERMINE /INVEST 92L
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(T. F. “Storm” Walsh III)
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CURRENT 2016 ATLANTIC TROPICAL CYCLONE TOTALS:
TOTAL STORMS: 8
MAJOR HURRICANES: 1
StormW’s Seasonal Hurricane Forecast:
TOTAL STORMS: 13-15
INTENSE HURRICANES: 3-4
Good day everyone!
PTC (Post Tropical Cyclone) HERMINE continues to drift slowly toward the west. As of the 11:00 a.m. EDT advisory from the NHC, the following information was available on HERMINE:
11:00 AM EDT Tue Sep 6
Location: 39.5°N 71.9°W
Moving: W at 3 mph
Min pressure: 997 mb / 29.44 in
Max sustained: 60 mph
Having lost the process of baroclinic forcing, and being over cool SST’s, HERMINE is expected to weaken and dissipate within the next 72 hours.
The cyclone is in a weak steering pattern at the moment, however analysis of forecast steering maps indicates that by Wed. a turn to the north may be in order, and eventually a turn toward the NE. As the upper low near the cyclone merges with it, a brief stall may occur, prior to the turn north.
Tropical Storm warning remains in effect for a portion of the NE. Residents within and near the warning area should monitor NOAA Weather Radio and local NWS statements and advisories.
LOCAL NWS STATEMENT LINKS
Elsewhere, INVEST 92L has become even more disorganized in the overnight hours. In fact, I am not sure at the moment if model data is even still being run on the system. The last update from ATCF regarding best track, was at 06Z this morning. The following was available on 92L as of 06Z:
2:00 AM EDT Tue Sep 6
Location: 15.1°N 70.0°W
Moving: W at 17 mph
Min pressure: 1010 mb / 29.83 in
Max sustained: 35 mph
The area continues to move toward the west, and appears to have slowed in forward speed, at least at the moment. Based on current and forecast steering maps, I expect this motion to continue during the next 72-96 hours, with a possible slowing in forward speed by 48 hours. There has been no dynamic or statistical guidance since ear;y this morning, which may indicate the ATCF/NHC may be getting ready to drop 92L from the data base. In fact, the morning graphical tropical weather outlook indicated the probability of cyclone development was lowered to 10% by the NHC.
Based on my analysis of the forecast steering maps however, this area of disturbed weather should continue into the Yucatan Peninsula near Belize in about 5 days. The steering forecast suggests the possibility of this weather could gain some slight latitude by 96 hours, as the steering pattern near the Yucatan becomes more WNW, then NW briefly, as a weakness in the ridge develops in the GOMEX. By 132 hours in the period from 12Z this morning, the forecast indicates steering may collapse over the GOMEX. Based on my analysis of this, whatever may be left could enter the BOC, and possibly stall once there.
I have been racking my brain this morning, trying to determine why 92L is having such a tough time trying to develop, and being so disorganized at the moment. Granted, upper level winds are not optimal, and the western portion of the circulation has been undergoing some shear, based on the last known position of the low, and forecast motion, an upper level anticyclone has developed very close to if not over the system, and the system remains east of an upper level low (which should be ventilating the area, providing some sort of outflow). The upper level wind pattern does indicate an outflow pattern taking shape, however it is centered more toward the heavier convection at this time. Maybe, this could be the problem at this time, and the fact the system had been moving quicker.
Dry air doesn’t seem to be a hindrance at the moment, based on water vapor imagery and TPW content.
The global models do not develop this, which has me scratching my head, as calculating future position of 92L, based on should it maintain it’s current forward speed, both the GFS and ECMWF agree on improving conditions for 92L within 48 to 72 hours, indicating the upper level anticyclone to be over the system, showing an increase in coverage and strength of the TPW content, as well as the system entering some very high OHC. Based on these factors, if the circulation survives, I would have to call for some very slow development as it enters the W. Caribbean, however the models do not develop this. I don’t remember if I have ever come across this situation, where conditions appear to be slowly improving, and are forecast to be much more favorable in 2-3 days, and not have development.
In any case, I will continue to monitor this area over the next 2-3 days.
Elsewhere, the Tropical Wave which moved off Africa, has been given a MEDIUM (60%) probability of becoming a cyclone during the next 5 days. Based on the current shear forecast, upper level winds are forecast to become a little more favorable for slow development during the next 72 hours, and indications are the pattern improves more by 120-144 hours, in which the wave may develop further.
Current and forecast steering indicates this system will most likely move to the WNW over the next 4-5 days. Based on the forecast positioning of the sub-tropical ridge, it is too early to speculate on whether this will be sacrificed to the re-curvature gods or not.
Elsewhere, I had detected another possible wave yesterday, which is now located near 13.0N;47.0W. Rotation is noted, and appears it may be not fully at the surface. Upper level winds are not favorable for development at this time, and dry air surrounds it. I did note in the TPW forecast however, this appears to track into the Bahamas in about 5-6 days (?), and the models show an dramatic increase in the TPW content. I will continue to monitor this, and will take another look in about 5 days.
Elsewhere, another area of disturbed weather near 7.0N;37.0W Appears to have become slightly better organized over the past few hours, with rotation noted in the mid levels. I believe this may have separated from a LLC which is located to the east of this feature. Upper level winds are marginal at the moment, however the pattern may become a little more favorable in about 48-72 hours as it continues to move toward the west. I am unsure as to why the NHC has not taken an interest in this area, having not placed it in the tropical weather outlook. I will continue to monitor this area over the next several days for any significant changes.
Have a blessed day!
T. F. “STORM” WALSH III
GMCS, USCG (ret)
METEOROLOGIST / HURRICANE SPECIALIST /SEVERE WEATHER SPECIALIST
MEMBER WEST CENTRAL FLORIDA AMS