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(T. F. “Storm” Walsh III)
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Good evening everyone!
I’ve been pouring over various forecast models, some which have updated, some which have not. This will be shorter than my preliminary pre-season forecast. Not much has changed in the forecast regarding the supposed onset of La Nina conditions, wind shear forecast. A slight change in the modeling does exist in the NINO 3.4 forecast plumes. There are some differences regarding the ECMWF (EUROSIP) seasonal modeling and the CFSv2 Climate model. I guess time will tell which one is correct. For all intents and purposes, based on everything I’ve pooled together, with what is available, I am expecting a transition to either NEUTRAL ENSO conditions (with a cold bias), to a MODERATE La Nina, based on the recent forecast plumes.
There was concern of the “cold pool” that was over the northern Atlantic, north of 40N. It is not fully known whether this will be a factor, and cool down any of the Atlantic MDR. Over the past few days, the Atlantic has warmed, and El Nino has waned further, albeit slowly. Having analyzed this, my belief at the moment is, La Nina may have temporary been slowed, as the current 30 day running mean of the SOI has been tanked strongly negative.
When the SOI is strongly negative, it is an indicator of stronger westerly wind over the Equatorial Pacific. Here is a brief explanation from the CPC regarding the SOI:
The Southern Oscillation Index (SOI) is one measure of the large-scale fluctuations in air pressure occurring between the western and eastern tropical Pacific (i.e., the state of the Southern Oscillation) during El Niño and La Niña episodes. Traditionally, this index has been calculated based on the differences in air pressure anomaly between Tahiti and Darwin, Australia. In general, smoothed time series of the SOI correspond very well with changes in ocean temperatures across the eastern tropical Pacific. The negative phase of the SOI represents below-normal air pressure at Tahiti and above-normal air pressure at Darwin. Prolonged periods of negative SOI values coincide with abnormally warm ocean waters across the eastern tropical Pacific typical of El Niño episodes. Prolonged periods of positive SOI values coincide with abnormally cold ocean waters across the eastern tropical Pacific typical of La Niña episodes.
So, with pressures being lower than normal at Tahiti, and above normal at Darwin, this creates westerly trade flow, as given the PGF (Pressure Gradient Force), air ALWAYS flows from higher pressure to lower pressure.
Once again I like to go with the ONI (Oceanic Nino Index) for choosing my analog years. Based on the 2016 ONI values, as well as the forecast NINO 3.4 plume forecast trend, the only analogs I can come up with are 1958 and 1998, with 1998 being the best of the two.
In 1958, there were a total of 10 named storms, 7 hurricanes, and 5 major hurricanes, including a CAT 5.
In 1998, there were a total of 14 named storms, 10 hurricanes, and 3 major hurricanes, including a CAT 5
So, based on reanalysis, some uncertainties in the equation, and making computations within the analog years, and short term and longer term averages, my official 2016 Atlantic Seasonal Hurricane Forecast stands as follows:
TOTAL NAMED STORMS: 12-14
TOTAL HURRICANES: 6-7
MAJOR HURRICANES: 3-4
Until I see a little more favorable progression of La Nina, and/or continued warming in the Atlantic, I cannot really justify going any higher in the numbers of the forecast.
Based on past research by Dr. James J. O’Brien (et al.) from FSU, it appears an increased probability of U.S. landfalls is not out of the question:
I will now be looking over model runs, and analyzing satellite loops in place of severe weather forecasting. I will however review the SPC site, and update on severe events as warranted.
This office will begin issuance of the Tropical Weather Forecast Synopsis on May 15, 2016 (yes, when the EPAC season begins). The purpose behind this will be to get myself back in the saddle of tropical forecasting, to familiarize newer subscribers to my product, and to watch against any PAC crossovers that may occur prior to June 01, 2016.
Have a blessed evening!
T. F. “STORM” WALSH III
GMCS, USCG (ret)
METEOROLOGIST / HURRICANE SPECIALIST /SEVERE WEATHER SPECIALIST
MEMBER WEST CENTRAL FLORIDA AMS