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(T. F. “Storm” Walsh III)
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Good day everyone!
The Hurricane Season officially begins TOMORROW! PLEASE, take this time to review your hurricane preparedness and evacuation plans.
Tomorrow officially kicks off the 2017 Atlantic Hurricane Season. I will not be posting tomorrow, as I work Thu., Fri. and Sat., so am posting this now.
Earlier in the year, climate models were pointing toward a moderate El Nino event during the hurricane season. As we have gotten into the period where climate model forecasts regarding ENSO predictions tend to be more accurate, the majority of the models tend to agree for neutral with slightly warm biased conditions in the NINO 3.4 region. Again, after analysis of SST anomaly maps from various climate models, and Nino plumes, and comparison of some past SST anomaly maps, the information at hand indicates we should experience a El Nino Modoki setup.
This type of El Nino setup, does not tend to produce a negative impact on the Atlantic Hurricane Season. One of the more noted Modoki years was 2004, in which we experienced a total of 15 named storms, 9 hurricanes, 6 of those hurricanes becoming major hurricanes (15-9-6). Depending on which average you use, and average season consists of 12-6-3 (latest 30 year average), or 10-6-2 (long term average of 100+ years).
Based on ALL of the analysis and re-analysis I performed over the last 2 weeks, my prediction for the 2017 hurricane season is as follows:
Named Storms: 12-15
Maj. Hurricanes: 3-4
These totals are based on comparison of previous Modoki years, trend and values from the ONI (Oceanic Nino Index), SST anomaly forecasts compared to previous Modoki years, and the combined average of the chosen analog years.
With that being said, the Atlantic and Caribbean basins are tranquil at the moment. Satellite loop imagery does indicate some flareup of shower and thunderstorm activity in the GOMEX. This shower activity is being produced from a combination of an upper level, semi-divergent pattern, and enhancement from the SSE flow coming across the Yucatan from Tropical Depression TWO-E in the EPAC.
NOAA WESTERN ATLANTIC SATELLITE LOOP (CLICK IMAGE FOR LOOP)
Based on the NHC advisory discussion on TD 02E, the official forecast calls for the depression to remain in the EPAC, but come very close to, or on the Mexican shoreline.
From the NHC forecast discussion:
The initial motion is 035/3. A mid- to upper-level trough seen in
water vapor imagery over northern Mexico is expected to steer the
cyclone slowly northeastward for the next 36 h or so. After
that, there is significant divergence in the track guidance. The
GFS, Canadian, and HWRF models move the cyclone inland over
southeastern Mexico in 48-60 h, while the ECMWF and UKMET show the
system stalling over the Pacific as a weak mid-level ridge builds
to the north. The latter part of the track forecast somewhat
splits the difference between these two solutions, showing the
cyclone remaining over the Pacific but closer to the coast of
Mexico than forecast by the ECMWF and UKMET.
Analysis of track guidance models tends to indicate this, with some of the guidance still wanting to show a crossover into the GOMEX. Based on the discussion where the NHC mentions a weak mid level ridge should build north of the area after about 48 hours, which is backed up now by some of the forecast steering layers maps, the depression should follow the forecast path. Now, I know the question everyone has…can this still crossover. The answer is…it IS possible to some extent, however this will all depend on whether the models are correct in that ridge materializing, when it builds north of the area, and the strength of the ridging. I am confident at the moment in the NHC forecast, however I WILL be monitoring the progress of that depression, given that we have all seen how quick conditions can change. In the event it does crossover, chances for any regeneration would be slim, given the wind shear forecast for the Gulf of Mexico (GOMEX).
Based on my analysis of the 12Z run of the global models, the GFS and ECMWF models do indicate a moderate lowering of pressures in the GOMEX in about 5-6 days. It is noted, that the GFS and ECMWF were displaying almost the exact same graphic. The CMC (Constantly Making Cyclones) is the only global model indicating and organized low pressure system, a TD if you will, at 995 mb, near the Florida Panhandle at 144 hours out. None of the other global models indicate anything organized over the next 5-7 days.
GFS MSLP NORMALIZED ANOMALIES
CMC MSLP 144 HOURS
Based on my analysis of the current wind shear forecast from the GFS, I do not anticipate any organized system in the GOMEX, unless the shear pattern takes an abrupt change.
GFS CURRENT WIND SHEAR FORECAST
Having mulled over this, my thinking is, a piece of energy from the PAC system may get pulled into the GOMEX, and there could be the possibility for weak low pressure to develop, and make its way NE to ENE, providing rainfall from LA to FL.
Other than that, the next period in which conditions appear favorable is around 144 hours from 12Z this morning, or 6 days out, over the W. Caribbean area. The GFS indicates wind shear will diminish over the W. Caribbean, and the CHI 200mb Vertical Velocity forecast indicates strong divergence aloft, with strong upward vertical velocities. Strong upward vertical velocities indicate divergence aloft, which in turn should create convergence at the surface, which can lead to lowering surface pressures. Given that, I will be focusing on that area when the time arises.
GFS GLOBAL WIND SHEAR MAPS
GFS CHI 200 VERTICAL VELOCITY FORECAST
Elsewhere, Tropical Storm formation is not expected during the next 7-10 days.
Have a blessed day!
T. F. “STORM” WALSH III
GMCS, USCG (ret)
METEOROLOGIST / HURRICANE SPECIALIST /SEVERE WEATHER SPECIALIST
MEMBER WEST CENTRAL FLORIDA AMS