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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: 1
Good day all!
The NHC must be as bored as I am. They have taken an interest in the tropical wave I have been speaking of over the past 2 days, and have added it to the Tropical Weather Outlook. The NHC has designated a LOW (20%) probability of cyclone development during the next 5 days.
Satellite loop images indicate there is very minimal convection associated with this wave.
Mid and upper level water vapor images indicate although water vapor in the mid levels is not ample, dry air at the moment doesn’t seem to be over powering. However, although both the GFS and ECMWF indicate ample relative humidity at the 850 – 700 mb levels, the 500 mb analysis indicates the possibility of some slight drier air intrusion to the waves NW. A slight layer of dust can be seen in the SAL true color channel.
MID LEVEL WATER VAPOR
UPPER LEVEL WATER VAPOR
TRUE COLOR IMAGE
Both the GFS and ECMWF had initialized moderate to high TPW values associated with the wave.
Analysis of the current wind shear product indicates upper level winds to be somewhat favorable with a semi diffluent flow. Albeit the pattern is not entirely favorable, wind shear values are only running 5 – 10 kts over the wave at the moment. This would allow for growth in the vertical, should this wave be able to produce convection.
CIMSS WIND SHEAR MAP
The shear forecast from the GFS does indicate a somewhat improving during the next 72 hours.
GFS WIND SHEAR FORECAST
Based on the above analysis, this wave should theoretically be able to show signs of further, slow organization during the next 72 hours. The GFS doesn’t indicate development, the ECMWF indicates a very small surface low in the MSLP normalized anomalies, and vorticity at 850 mb, then dissipates it. The CMC develops this, or the wave coming out next, and develops a Tropical Storm. I have to call out the CMC on this at the moment, as at the day 7 position, which indicates a decent Tropical Storm, both the ECMWF and GFS indicate increased westerly wind shear over that location.
CMC 7 DAY AND 10 DAY FORECAST
Given the poor state of the wave at the moment, I am not all too sure about it fighting off the drier air to its north and NW. The wave is currently moving slowly to the west, at near 12 mph, and based on forecast steering, should continue on a west to WNW motion over the next few days, before ridging builds westward, allowing for a more west motion. At this time, I concur with the NHC probability, and will continue to monitor conditions for any significant changes.
Elsewhere, various indicators for tropical forecasting still show the presence of improving conditions by the end of this month, and into Aug. 02. The MJO forecast calls for a favorable, or upward motion signal of the MJO to continue progressing into the Atlantic basin by week 2 in the forecast period.
CURRENT MJO FORECAST
MJO filtered VP200 anomalies for the current state, for the week 1 forecast, and for the week 2 forecast.
Cold colors are representative of a more favorable state over the Atlantic for tropical cyclogenesis (typically after the passage), and warm colors represent a less favorable state for tropical cyclogenesis.
The presence of a forecast CCKW in combination with the MJO is still forecast, and the 200 mb Vertical Velocity Potential Anomalies forecast indicates upward vertical motion. by months end, into the first week of Aug. Blues and violets are indicative of upward motion, which indicates divergence aloft, and convergence at the surface. This can, and often does increase the potential for tropical development.
MJO CCKW FORECAST
200 MB VERTICAL VELOCITY POTENTIAL ANOMALY FORECAST
The current 200 mb Vertical Velocity Potential Anomaly map indicates the opposite at the moment.
CURRENT 200 MB VERTICAL VELOCITY POTENTIAL ANOMALY MAP
Another index which indicates the relative strength of the subtropical ridge, the NAO (North Atlantic Oscillation) is forecast to be relatively negative during the next couple of weeks. This means a weakening of the ridge, which will alleviate the subsidence we are seeing. Based on these factors, we should see an increase in tropical activity. A word of note however, when these changes occur, DO NOT expect instant karma. I had done some research last season in regards to the MJO (and damned if I can find the article) in which the article stated, activity usually increases (I believe 5 days was the timing criteria) after passage or entrance of the MJO signal. This would tie into my thinking that we begin t get active beginning around the last of the first week of Aug, to the beginning of the second 10 days (10-20th).
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