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(T. F. “Storm” Walsh III)
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STORM W’s SEASONAL HURRICANE FORECAST
TOTAL STORMS: 14-16
MAJ. HURRICANES: 3-4
MAJ. HURRICANES: 0
U.S. LANDFALLS: 2
Good day all!
Ok. Folks have been asking everyday, WHEN is the hurricane season going to become active. There have been quite a few folks who have felt the season forecast may wind up as a bust. Well, I know a lot of you remember me saying “be careful what you wish for”? Well, folks just couldn’t leave well enough alone (LOL!). SOMEONE woke up Mother Nature…and looking at some things down the road, she could be angry. For what it’s worth, Joe Bastardi from Weatherbell Analytics, is once again referencing the upcoming pattern, forecast by the Japanese climate model, for the 500 mb pattern, as an analog of 2004.
We finally have an increase in activity, with 2 disturbances to watch.
The NHC has designated a LOW (20%) probability of cyclone development for INVEST 90L during the next 5 days, and a HIGH (70%) probability for INVEST 99L.
Tropical Disturbance INVEST 90L is currently located in the eastern Caribbean Sea. As of the 18Z ATCF BTK product, the following was available on INVEST 90L
2:00 P.M. EDT AUG. 03, 2017
MAXIMUM SUSTAINED WINDS…30 MPH
PRESENT MOVEMENT…W AT 18 MPH
MINIMUM CENTRAL PRESSURE…1013 MB…29.91 INCHES
Analysis of satellite loop images indicate 90L to have a broad circulation which is currently disorganized.
Analysis of the current wind shear product from CIMSS indicates the presence of an upper level anticyclone over the system which appears to be newly developed. Based on analysis of the global models GFS and ECMWF, this upper feature is forecast to dissipate in the next 24 hours, then begin to become re-established at 96 hours from 12Z this morning. The problem is, with the upgrade to the GFS, which appears to have downgraded its performance, which model do we trust in the shear forecast? The reason I say this is, we haven’t seen anything proven from the GFS yet, since the upgrade, so this will be the chance to see if it’s performance has been downgraded or not. The GFS indicates not so favorable of a shear environment, while the ECMWF shows a strong upper level anti-cyclone over the GOMEX by 144 hours.
CURRENT WIND SHEAR
GFS SHEAR FORECAST
ECMWF SHEAR FORECAST
IF the ECMWF is the correct solution, then we could see a 60-70 mph T.S. in the GOMEX in 6 days. IF the GFS is correct, then we would see a weak, open wave. Based on this, the only way to handle this system is in real time information (wind shear, TPW, RH, etc.).
The disturbance is currently moving to the west, and I expect this motion to continue for about the next 72- 96 hours. A turn more to the WNW could occur thereafter, as a weakness in the ridge may occur over the extreme NW GOMEX. As it stands at the moment, this may make landfall in Mexico, however this, and track guidance should be considered preliminary at the moment, given the system is currently disorganized.
Elsewhere, Tropical Disturbance INVEST 99L is located in the far eastern Atlantic, SSE of the Cabo Verde Islands. As of the 18Z ATCF BTK product, the following was available on INVEST 99L
2:00 P.M. EDT AUG. 03, 2017
MAXIMUM SUSTAINED WINDS…30 MPH
PRESENT MOVEMENT…W AT 17 MPH
MINIMUM CENTRAL PRESSURE…1010 MB…29.83 INCHES
Satellite loop imagery indicates the disturbance is disorganized at the moment, and is lacking any deep convection. The last few frames of the loop may indicate the mid to low level circulation may be trying to slowly organize.
Based on the recent CIMSS wind shear analysis, INVEST 99L did have an upper level anti-cyclone over it, however this has not translated down yet to the 350-300 mb level, and there is no well established outflow channel as of yet.
INVEST 99L CIMSS WIND SHEAR
The current wind shear forecast is again, up in the air. GFS shows an upper level anticyclone to remain with the disturbance during the next 6 days, then weakens the upper feature. The ECMWF indicates pretty much the same, with less ridging over the system, and NAVGEM with a decent upper level anticyclone. So the dilemma remains, which model is correct as far as strength, as again, nothing has been proven yet with the accuracy of the GFS, and I guess this will be its chance to either shine or fail. If the upper air pattern holds per the GFS and NAVGEM, I cannot rule out a hurricane in 5-7 days. IF the ECMWF is correct, we could only see a depression (?). Again, I never really go with the models on initial forecast intensity, as the system is disorganized, and initialization of these parameters is less than accurate. Intensity of this will depend on 2 things, the upper air pattern, and track. GFS and CMC right now bring this toward the SEUS, then indicate re-curvature, while the ECMWF keeps a weaker system, brings it over the Greater Antilles, then indicates a wave west of Jamaica in 8 days. Based on current forecast steering layers maps, and the NHC 5 day estimated position in the GTWO, 99L may not feel the weakness in the ridge. Keep in mind however, the weaker the system, more westward it comes. The stronger the system, more poleward it goes. As with 90L, real-time analysis and forecasting will be the order, until the system becomes well defined, and models have a better entity to work with. IF some forecast conditions I’ve looked at materialize, expect 99L to become better organized in about 3 days.
I will be monitoring both systems over the next few days for any significant changes, but will not be able to update until late Sunday afternoon to evening.
Based on analysis of 200 mb Vertical Velocity Potential Anomalies,and forecast, and the MJO forecast, we could begin to see a very busy time. The first map is of today. As I have stated before, the blues and purples are favorable for TC development, as it indicates upward motion in the atmosphere, and divergence aloft. This is why we now have 99L. The next 2 maps after that, is the current forecast.
CURRENT 200 MB VERTICAL VELOCITY POTENTIAL
FORECAST 200 MB VERTICAL VELOCITY POTENTIAL
The following is the MJO forecast, which indicates favorable conditions.
Elsewhere…I am not expecting tropical storm development during the next 5-7days.
Have a blessed day!
T. F. “STORM” WALSH III
GMCS, USCG (ret)
METEOROLOGIST / HURRICANE SPECIALIST /SEVERE WEATHER SPECIALIST
MEMBER WEST CENTRAL FLORIDA AMS