TROPICAL CYCLONE FORMATION: INVEST 98L (30%)
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(T. F. “Storm” Walsh III)
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CURRENT 2016 ATLANTIC TROPICAL CYCLONE TOTALS:
TOTAL STORMS: 5
INTENSE HURRICANES: 0
StormW’s Seasonal Hurricane Forecast:
TOTAL STORMS: 13-15
INTENSE HURRICANES: 3-4
Good day everyone!
The area of disturbed weather I mentioned in yesterdays forecast, was designated INVEST 98L yesterday evening by the NHC. The NHC has designated a LOW (30%) probability of tropical cyclone formation during the next 5 days.
Various modeling indicates some higher probability of development.
Based on information contained in the ATCF BTK product as of 12Z, the following was available on INVEST 98L:
8:00 AM EDT Mon Aug151
Location: 9.2°N 23.7°W
Moving: W at 15 – 18 mph
Min pressure: 1009 mb/29.80 in
Max sustained: 25 mph
The disturbance is currently moving toward the west, with a 24 hour average speed of 15-18 mph. INVEST 98L is currently being steered by the southern periphery of the sub-tropical ridge. At the moment, I am in some disagreement with the future projected track in the NHC GTWO, and with the current 12Z dynamic track guidance. I am having a tendency to somewhat agree with the current ECMWF forecast track, however based on my analysis of the current steering layer mean, and forecast steering maps from the PSU E-wall site, I believe a more westward track will be in order, as current steering, and satellite loop imagery indicates a pretty straight east to west flow at the moment. IF the current run of the forecast steering maps is accurate, I expect a west, to slightly north of west track to continue for at least the next 36 hours, possibly 48 hours, before a weakness in the ridge occurs at around 45W. Based on satellite loop imagery, noting low and mid level cloud motion, combined with the forecast steering layers maps, I am just not buying the quick turn toward the WNW-NW as depicted in dynamic guidance. IF dynamic guidance beats me, then as in the past, I’ll have to re-analyze what has been looked at in analysis.
INVEST 98L hasn’t change much in organization in the past few hours, and appears elongated at the moment. Based on the recent wind shear product from CIMSS, a weak upper level anticyclone was established over the disturbance, and the disturbance was located in a high TPW environment.
Water vapor loop imagery indicates there may be enough moisture for INVEST 98L to fight off any African dust.
Based on my analysis of the GFS wind shear product, the upper level anticyclone is forecast to diminish somewhat, but could become re-established over the system in 2-3 days. Analysis of forecast shear magnitude from the NOAA RUC HFIP TCDIAG. page, indicates the ECMWF and GFS both call for shear to decrease to below 10 kts within the next 36 hours.
Should this come to fruition, save any significant dry air intrusion, I am calling for further slow strengthening of INVEST 98L. Current ATCF Intensity guidance indicates the more reliable intensity models bring 98L to strong Tropical Storm to Minimal CAT1 Hurricane status in 4-5 days. Given that both track guidance and intensity guidance have just been initialized, I am just going to keep this in the back of my mind, until modeling can complete a couple of more runs, or until 98L possibly becomes better organized…however if the shear forecast is correct, I CANNOT rule out the intensity guidance at the moment.
I will continue to monitor INVEST 98L for any significant changes during the next 2 days.
Elsewhere, if the global models are correct…STANDBY. As of this mornings run of the GFS and ECMWF, believe it or not, both models are in uncanny agreement of activity increasing over the next 7-10 days, indicating a total of 3 active systems before the end of the month. Based on my analysis of the models this morning, both the ECMWF and GFS eventually re-curve 98L, and another system that is forecast to exit Africa a little further north than an area forecast to exit Africa at the same time frame, in about 5-6 days. This can be seen in both the GFS and ECMWF. The system that exits further south, is projected by the models to come to around 50W, before making a turn to the WNW. Based on analysis of the medium to long range 500 mb pattern, this feature should feel a weakness off the U.S. east coast, which will bring it to the WNW. However, indications are this weakness may be the precursor to a trof split, where the main piece will shoot NNE, and another backs away toward the GOMEX. IF this occurs, the possibility of ridging building back over the feature, COULD bring it close to FL. or the U.S. coastline. This is not written in stone, but is one possible scenario, should the activity occur. Right now, I cannot rule this uptick out, as the recent forecast of the 200 mb velocity potential anomalies indicates favorable conditions during the next 5-7 days. The current NASA TPW forecast still indicates moist surges to continue to exit Africa.
GFS MSLP ANOMALY FORECAST
ECMWF MSLPA FORECAST
Analysis of the 500 mb anomaly maps tends to indicate we may see the African wave train come more to life in about 7-10 days, as lowering pressures are noted over the African continent.
Elsewhere, Tropical Storm formation is not expected during the next 5-7 days
T. F. “STORM” WALSH III
GMCS, USCG (ret)
METEOROLOGIST / HURRICANE SPECIALIST /SEVERE WEATHER SPECIALIST
MEMBER WEST CENTRAL FLORIDA AMS