2023 HURRICANE SEASON PRELIMINARY FORECAST…ISSUED MAR. 19, 2023…6:25 P.M. EDT

Disclaimer:  This site is not affiliated with the National Hurricane Center, Hurricane Hunters, Storm Prediction Center, or National Weather Service.  ALL forecasts herein are the result of my analysis, (to which you will see me at times, insert excerpts from various agencies due to the nature of the importance of the information) and I am solely responsible for the content.  As ALWAYS, follow the National Hurricane Center, National Weather Service, and your local Emergency Management officials for emergency decisions.  In addition, this is strictly a FORECAST OFFICE.  I CANNOT make decisions regarding travel plans, etc.  My purpose, is to provide you the information, based solely on information I analyze, and the accuracy of the information at hand of the time of analysis, so you may make informed decisions.
(T. F. “Storm” Walsh)

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I will reiterate, my forecasts are based on the available information at the time of analysis, and are only as accurate as the information analyzed and the solutions provided.

Good evening everyone!

Based on analysis of  the most CURRENT forecast information from various global and climate models, it appears at the moment, the 2023 Atlantic Hurricane Season COULD be a “below average” season.  As always, this forecast is subject to change as forecast models will continue to update between now and June 01 on a monthly basis.  However, as it stands with the available information, it looks like we may experience a below average season.  I will reiterate once again, when I post my pre-season, and final seasonal forecasts, the totals are based on BONA FIDE storms, not some of the crap we saw named last season, and seasons previous.  I’m speaking of storms that meet the NWS/NHC criteria.  First, the system has to start out as a Tropical Disturbance, and as it strengthens, it becomes a depression, storm, and then hurricane:
Tropical Disturbance:
A discrete tropical weather system of apparently organized convection — generally 100 to 300 nmi in diameter — originating in the tropics or subtropics, having a nonfrontal migratory character, and maintaining its identity for 24 hours or more. It may or may not be associated with a detectable perturbation of the wind field.

Please note some of the “key” features:  apparently organized convection, nonfrontal migratory character, and maintaining its identity for 24 hours. Last season, and in some prior seasons, we saw naked swirls being called depressions, and all of a sudden, if a thunderstorm popped up, or an area of deep convection fired up, mainly on the edge of the center, all of a sudden it got named.  This does not meet the criteria of apparently organized deep convection, maintaining its identity for 24 hours.  They also named systems that had a frontal system still attached, or decaying front through the center of the system.  Keep this in mind if you are following this site and the active storms…look for the criteria.

The following is my PRE-SEASON outlook forecast for the upcoming 2023 Atlantic Hurricane Season.  These totals are almost surely to change, as climate modeling continues to update between now and June 01, 2023:

STORM W PRE-SEASON FORECAST
TOTAL NAMED STORMS:  11– 12
TOTAL HURRICANES :        5 – 7
MAJOR HURRICANES:        2 – 3

AVERAGE HURRICANE SEASON:
TOTAL NAMED STORMS: 14
TOTAL HURRICANES:         7
MAJOR HURRICANES:        3

Forecast parameters used in this synopsis include the following:
1.) CLIMATE MODEL ENSO PLUME FORECASTS
2.) SST ANOMALY FORECAST
3.) IOD (Indian Ocean Dipole) FORECAST
4.) WIND SHEAR FORECAST
5.) ONI (Oceanic Nino Index) FORECAST TEMPERATURES AND TRENDS
6.) AVERAGING OF CHOSEN ANALOG YEARS BASED ON CPC ONI HISTORY
Based on analysis of updated forecast ENSO plumes from global and climate modeling, and updated ONI forecast temperatures and trends, the majority of models seem to indicate the onset of El Nino conditions with conditions forecast to become NEUTRAL this month into April.  As a rule of thumb, the cooler NINO 3.4 becomes, the more favorable conditions over the Atlantic become for storm development, with the opposite effect of a warmer NINO 3.4 region.  By JUL- AUG time-frame, it appears we enter moderate El Nino conditions.  Based on this, our season “may” start out “normal” in June through a portion of July, as there is generally a 2 month “lag time” between El Nino oceanic conditions, and atmospheric coupling.  The SOI or Southern Oscillation Index currently indicates the atmosphere is in a “neutral” ENSO state.  When this graph is in “positive” territory, it indicates La Nina conditions in the atmosphere, while “negative territory tends to indicate El Nino conditions in the atmosphere.  Typically, the lag time is about 2 months.  This means for the atmosphere to be declared in either El Nino or La Nina state, the graph has to be either +7 or -7 for at least 2 months.  Here is a little explanation from the BOM:
Sustained positive values of the SOI above +7 typically indicate La Niña, while sustained negative values below −7 typically indicate El Niño. Values between +7 and −7 generally indicate neutral conditions.
CLIMATE MODEL NINO PLUMES FORECAST GRAPHS:
NCEP

NMME ENSEMBLE

BOM (AUSTRALIA BUREAU OF METEOROLOGY)

NASA GEOS

UKMET

ECMWF

IRI / CPC

CURRENT SOI

The following SST anomalies forecast is from the CFSv2 climate model and NMME model, and currently indicates the forecast El Nino pattern:
CFSv2 SST ANOMALIES FORECAST JUNE THROUGH OCTOBER

NMME SST ANOMALIES FORECAST JUNE – SEPTEMBER


CURRENT SST ANOMALIES

You’ll note in the SST anomalies forecast maps,  the anomaly pattern shows an extensive tongue of warmer anomalies from the west coast of South America, westward, and warmer anomalies north of the MDR.

I’m going to discuss two other important factors regarding development over the Atlantic ocean.  The first involves the Gulf of Guinea.  The second involves the IOD (Indian Ocean Dipole).
The Gulf of Guinea is the northeastern most part of the tropical Atlantic Ocean from Cape Lopez in Gabon, north and west to Cape Palmas in Liberia.

I am going to forgo mentioning what the climate models indicate about the Gulf of Guinea forecast temperature anomalies, as they have not panned out over the past few hurricane seasons.  I will however state the role played by the Gulf of Guinea.  When the Gulf of Guinea is warmer than average/normal (warm anomalies) or a warm neutral, the ITCZ has the tendency to remain further south, (Equatorward) during the season.  This is what occurred in the 2021 hurricane season, as we saw many tropical waves exit below 10 degrees north latitude.  In addition, we saw many SAL occurrences, even into August.  The heaviest of the SAL outbreaks climatologically occur in the month of July.  With the ITCZ further south, it doesn’t extend into the Sahel region of Africa, hence drier conditions and more dust.  When the Gulf of Guinea experiences cooler anomalies (colder than normal), it allows for a shift northward in the ITCZ/Monsoon, due to the reverse pressure pattern, bringing greater rainfall to the Sahel region, which would aid in a reduction in the SAL.
GULF OF GUINEA

Another item in the forecast regarding Sea Surface Temperature Anomalies is the IOD (Indian Ocean Dipole).  The forecast from climate modeling tends to show the IOD going “positive” around the beginning of June, then heading to a stronger positive signal as the season progresses.  This would be a negating factor in hurricane development.  During a positive IOD phase, you’ll notice the “Walker” circulation allowing for an increase in convection and rain near east Africa.  The rising air causes lower pressure and precipitation at the ocean surface.  You’ll see on the eastern side of the circulation, air sinks to the surface, causing higher pressure at the surface and drier conditions.  Well, it just so happens, this exact flow happens on the western portion of the circulation.  The air rises, and as it reaches the upper portion of the atmosphere, it cools, then begins to sink (higher pressure).  As this air in the upper atmosphere sinks, it compresses and heats, drying out the air, hence the “lack” of convection for easterly waves.  A negative IOD phase has the opposite effect.  As the air “sinks” over the western Indian Ocean, it spreads out over the surface, and across eastern Africa.  The pattern then continues with the air “rising” over central Africa, allowing for, or aiding in the formation of convection.
IOD SST ANOMALIES NEGATIVE / POSITIVE

IOD POSITIVE PHASE

IOD NEUTRAL PHASE

IOD NEGATIVE PHASE

CURRENT IOD FORECAST FROM BOM, UKMET, AND NASA GEOS

With the forecast of a moderate El Nino, the CFSv2 is showing somewhat above average wind shear over the Atlantic basin (MDR) for a portion the season, and average to below average north of the MDR. Shear over the MDR is another negating factor for the hurricane season.
CFSv2 CURRENT SEASONAL u200 – u850 (WIND SHEAR) FORECAST

Again, as all of these parameters update during the next 3 months, adjustments may have to be made, prior to issuing a final seasonal forecast.

Based on analysis of forecast ONI values from the IRI (International Research Institute), which uses 26 different climate models, I came up with the following past hurricane seasons as analog years: 1951, 1963, 2002, and 2009.  I determined this from ONI values and / or value trends based on the average of ALL the climate models, comparing them to the CPC ONI chart, with the years that matched the forecast anomalies, and/or anomaly trends.  The IRI provides an average of the Dynamical models, Statistical models, and an average of ALL 26 models output.

The ONI explained from the site, HDX:
Monthly Oceanic Nino Index (ONI)
The Oceanic Niño Index (ONI) has become the de facto standard that the National Oceanic and Atmospheric Administration (NOAA) uses to identify El Niño (warm) and La Niña (cool) events in the tropical Pacific. It is the three month mean SST anomaly for the El Niño 3.4 region (i.e., 5°N-5°S, 120°-170°W). Events are defined as five consecutive overlapping three month periods at or above the +0.5°C anomaly for warm (El Niño), events and at or below the -0.5 anomaly for cold (La Niña) events. The threshold is further broken down into Weak (with a 0.5 to 0.9 SST anomaly), Moderate (1.0 to 1.4) and Strong (≥ 1.5) events. For an event to be categorized as weak, moderate or strong. it must have equaled or exceeded the threshold for at least three consecutive overlapping three month periods.
IRI ONI FORECAST

CPC ONI CHART

Based on the average of the 4 analogs (10.8 storms total, 5.5 hurricanes and 2.3 major hurricanes),  my pre-season forecast totals were derived in this manner, however reflect current uncertainties in forecast conditions .

If you would like a copy of the Hurricane Preparedness post, or previous Hurricane Tutorials, please send me an email.

You may direct any questions this season by contacting me personally, ANYTIME, at: twalsh22000@yahoo.com

Have a blessed evening!

T. F. “STORM” WALSH III
GMCS, USCG (ret)
METEOROLOGIST / HURRICANE SPECIALIST /SEVERE WEATHER SPECIALIST
MEMBER WEST CENTRAL FLORIDA AMS