TROPICAL CYCLONE FORMATION: T.D. JULIA / T.S. KARL / INVEST 96L (80%)
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(T. F. “Storm” Walsh III)
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CURRENT 2016 ATLANTIC TROPICAL CYCLONE TOTALS:
TOTAL STORMS: 11
MAJOR HURRICANES: 1
StormW’s Seasonal Hurricane Forecast:
TOTAL STORMS: 13-15
INTENSE HURRICANES: 3-4
Good day everyone!
Julia is currently a Tropical Depression. As of the 5:00 p.m. advisory, the following information was available on Julia:
5:00 PM EDT Sun Sep 18
Location: 32.3°N 78.0°W
Moving: NNW at 7 mph
Min pressure: 1010 mb / 29.83 in
Max sustained: 30 mph
Based on the most recent steering layer mean map, Julia has been in a weak to almost non existent steering regime, which has allowed for the depression to drift toward the west during the afternoon. This can be noted in satellite loop imagery of the exposed LLC. Julia is now moving to the NNW, and based on current updated forecast steering layers maps, I expect a turn toward the north to begin later tonight. Right now, there is a split as to whether or not Julia gets picked up by an approaching front, or moves SSW as a weak remnant low.
Based on analysis of the current wind shear forecast, shear over Julia at the moment is forecast to relax, with the establishment of an upper level anticyclone over the area for a breif period. This may allow for her to become slightly better organized, which could lead to some slight strengthening. The 2 things in her favor will be the decrease in wind shear, and the warm Gulfstream. The limiting factor may be the dry air around her noted in water vapor imagery. Based on this analysis, I have to concur with the NHC at the moment, on both track and intensity.
NHC INTENSITY FORECAST
INIT 18/2100Z 32.3N 78.0W 25 KT 30 MPH
12H 19/0600Z 33.0N 78.0W 25 KT 30 MPH
24H 19/1800Z 34.0N 77.7W 30 KT 35 MPH
36H 20/0600Z 34.6N 77.5W 30 KT 35 MPH…INLAND
48H 20/1800Z 34.9N 77.5W 25 KT 30 MPH…INLAND
72H 21/1800Z 34.2N 78.2W 20 KT 25 MPH…POST-TROP/REMNANT LOW
Elsewhere, Tropical Storm Karl has become a little better organized over the past few hours. Earlier this afternoon, satellite imagery indicated somewhat of a sheared storm, due to some SWLY wind shear. However, NHC indicates the shear is beginning to relax, and based on my analysis of current RGB and visible satellite loop imagery, this seems to be occurring, as the exposed LLC now has convection popping up on the very eastern edge of the LLC with an overshooting top noted in the convective cloud burst. As of the 5:00 p.m. advisory from the NHC, the following was available on Karl:
5:00 PM AST Sun Sep 18
Location: 18.3°N 45.0°W
Moving: W at 15 mph
Min pressure: 1006 mb / 29.71 in
Max sustained: 40 mph
Karl has been moving more toward the west during the day, and I expect this motion to continue for about the next 36 hours, before more of a WNW motion occurs. Based on current steering layers forecast maps, the WNW motion should continue through to day 5 in the forecast period. Beyond that, based on my analysis of the current run of the GFS and ECMWF 500 mb anomaly maps, a break develops in the subtropical ridge, just west of Bermuda, and Karl is forecast to head into this break. The steering layers forecast maps indicate steering may be weaker at that time, so this motion could be slow through the break in the ridge. A lot will depend on how strong or weak Karl may be by day 5, as to whether or not forward motion may be slow enough, and if he is weaker than forecast, the very slim possibility exists in missing this connection. However as it stands at the moment, models are in agreement of the storm heading into the break in the ridge by day 5 into day 6, and shortly into day 6, a strong 500 mb trof is forecast to dip far enough south, to take Karl out to sea. At the moment, this seems to be the most plausible scenario, and I have to concur with it and the NHC forecast track at the moment, which is inline with the 18Z dynamic guidance. However, I am looking to see what happens in a few days with the ridge/trof pattern and if the forecast for it holds. In any case, I’ll know much more by day 4-5 in the period.
GFS 500 MB ANOMALY MAPS
Given the premise of forecast favorable upper level winds, albeit the premise of some dry air intrusion is forecast, this should limit the rate of intensification over the next few days, until the storm becomes a hurricane, which is now forecast by day 5 to be a 90 mph Category one hurricane. Based on the premise of the shear relaxing to below 10 knots soon, and zonal shear forecast to be around zero at various times in the forecast, I have to concur with the NHC intensity forecast. Should the forecast hurricane be able to be efficient at mixing out the dry air, the possibility could exist at Karl making a run for a breif CAT 2 storm.
NHC INTENSITY FORECAST
INIT 18/2100Z 18.3N 45.0W 35 KT 40 MPH
12H 19/0600Z 18.5N 47.0W 40 KT 45 MPH
24H 19/1800Z 19.0N 49.7W 40 KT 45 MPH
36H 20/0600Z 19.7N 52.2W 45 KT 50 MPH
48H 20/1800Z 20.5N 54.7W 50 KT 60 MPH
72H 21/1800Z 22.9N 59.7W 60 KT 70 MPH
96H 22/1800Z 25.4N 64.2W 70 KT 80 MPH
120H 23/1800Z 28.0N 67.0W 80 KT 90 MPH
I will be monitoring Karl for any significant changes during the next 48-72 hours.
Elsewhere, INVEST 96L has been designated about a couple of hundred miles SE of the Cabo Verde islands. Based on the 18Z ATCF BTK product, the following information was available on 96L:
Location: 13.0°N 22.4°W
Moving: WNW at 6 mph
Min pressure: 1007 mb / 29.74 in
Max sustained: 35 mph
Based on the 12 hour average from 06Z to 18Z, the disturbance is moving WNW at around 6 mph. Based on forecast steering analysis, I expect this motion to continue for the next 24-36 hours, with more of a NW motion thereafter. Based on global models, this disturbance should re-curve in a few days.
Based on my analysis of the current and forecast shear pattern, the disturbance is currently under a favorable upper level pattern for further slow organization and strengthening, with the presence of an upper level anticyclone present at the moment. Indications are, this upper level anticyclone is forecast to remain over the system for at least the next 96 hours. 18Z intensity guidance indicates the disturbance could become a Tropical Storm within the next 18 hours, however I am calling for slower intensification at the moment given the structure at time of analysis. I cannot rule out the development of a Tropical Depression either very late tonight, or early tomorrow morning, if the slow organizational trend continues. Winds are up from 25 mph earlier today, to 35 mph this evening. Should organization begin to occur quicker, then the strengthening process would become quicker. Based on the premise of the favorable upper pattern, I do believe this may become our next Tropical Storm, but based on the current forecast track, I believe cooler SST’s and low OHC may inhibit the rate of intensification, and I feel at the moment, this may only become a Tropical Storm, vice a breif CAT 1 Hurricane as forecast by the SHIP and DSHP models. I will be monitoring this system over the next few days, however this should not be a concern for the central Atlantic or the U.S.
Elsewhere, Tropical Storm formation is not expected during the next 5-7 days.
Have a blessed day!
T. F. “STORM” WALSH III
GMCS, USCG (ret)
METEOROLOGIST / HURRICANE SPECIALIST /SEVERE WEATHER SPECIALIST
MEMBER WEST CENTRAL FLORIDA AMS