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(T. F. “Storm” Walsh III)
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Good day everyone!
UPDATE MAY 25, 2017: Having reviewed analog years once again, and the fact we have had one system already, I am making a final “tweak” to my seasonal forecast…please see the seasonal forecast section of this synopsis.
The BOM ENSO WRAP UP site has update, with new information on their forecast for the NINO 3.4 region forecast, and as promised, I am posting my final 2017 Seasonal Hurricane Forecast.
First, let’s begin with a graphic that shows the NINO regions by location:
NINO REGIONS MAP
The following are the forecast NINO plumes from various models, updated for May, 2017.
It is noted the ECMWF model is the most bullish for a developing El Nino. However, El Nino conditions if they occur, will most likely be right after the peak of the 2017 hurricane season.
ECMWF NINO PLUMES
NMME NINO 3.4 FORECAST PLUMES (ENSEMBLE MEAN AND ALL MEMBERS)
CFS v2 NINO PLUME FORECAST
BOM POAMA NINO 3.4 FORECAST (APR – MAY COMPARISON)
UKMET NINO PLUME FORECAST
As one can see, the trend overall has been downward in regions 1 & 2, slightly in region 3, region 3.4 fairly neutral and warming in region 4.
This coincides with the SST Anomaly forecasts:
ECMWF JAS – ASO SST ANOMALY FORECAST
CFS V2 SST ANOMALY FORECAST JAS – ASO
Here are SST anomalies from 2002 and 2004 for comparison:
SST ANOMALIES AUG – SEP 2004 (LINKED)
The following u200 – u850 wind anomaly charts represent wind shear. It appears during the peak of the season, wind shear should be below climatology, as indicated by the negative anomalies (blue shading)
CFS V2 WIND SHEAR FORECAST
Rainfall accumulations over west Africa have shown some deficits over the past 30 days. However, the current forecast is leaning toward slightly above normal rainfall over the Sahel region :
CPC AFRICAN DESK
CPC 30 DAY MEASURED RAINFALL
CURRENT 30 DAY DEFICIT
JUN – AUG PRECIPITATION PROBABILITY
JUL – SEP
Now, are these model outputs correct? Your guess is as good as mine, however the NINO plume forecast have been trending downward in the past few months, with most of the models in agreement.
If you note the SST Anomaly forecasts, which coincide with the NINO plumes, the anomaly forecasts are not too much indifferent than the years 2002 and 2004. Based on this, and the reanalysis of the CPC Oceanic Nino Index, both trend and temperature analysis, I came up with the analog years, which seem to fit the best profile, of 1951, 2002, and 2004. I especially feel comfortable with 2002 and 2004, in that pretty much resembling the SST anomaly forecasts, it appears that El Nino Modoki conditions are forecast, given the plumes in region 1 & 2 becoming cooler, with the higher heat content becoming focused in the central and western Pacific, with warming being shown especially in NINO region 4. This is not indicative of a “canonical” El Nino, but more so of a “Modoki” El Nino
CANONICAL EL NINO AND MODOKI EL NINO
The current forecast for the IOD (Indian Ocean Dipole) is for the IOD to become positive by some climate models, however could be within neutral range until winter. We’ll have to see how this affects the Cape Verde season, as a positive IOD would have the tendency to disrupt the west African monsoon circulation, which is usually a negative for a big Cape Verde season.
Based on the information at hand, should the model forecasts verify, and given the chosen analog years, my updated seasonal forecast is as follows:
TOTAL STORMS: 12-15
MAJ. HURRICANES: 3-4
This forecast does not mean the higher numbers will definitely be met, however based on the analogs, the higher totals were within range of one of the analogs.
The season officially begins June 01, 2017. PLEASE, take this time to review your hurricane preparedness and evacuation plans.
Have a blessed day!
T. F. “STORM” WALSH III
GMCS, USCG (ret)
METEOROLOGIST / HURRICANE SPECIALIST /SEVERE WEATHER SPECIALIST
MEMBER WEST CENTRAL FLORIDA AMS