Florida State Center Wiki: Climate Classification Of East Central Florida

Climate Classification of East Central Florida

The Glossary of Meteorology 2 defines a monsoon climate as one in which the wind flow reverses itself during the course of the year and there is a distinct winter dry season. Data examined in this study clearly indicates that there is a duality of seasons for east central Florida, with the cooler season being significantly drier than summer. Additionally, the mean wind during most of the east central Florida Wet Season is southeast (tropical) while the mean wind during much of the Dry Season is northwest to north (continental).

The Wet Season is marked by a daily inland progression of the Atlantic and Gulf of Mexico sea breezes as a low pressure trough develops across the peninsula due to surface heating. Showers and thunderstorms occur most days along the sea breezes and become numerous when these boundaries collide. While the low pressure trough that produces this sea breeze circulation is not on the same scale as the large heat lows that drive monsoon circulations elsewhere in the world, there is enough regularity to suggest some similarity. Trewartha (1968)3 refers to the daily sea breeze circulation as a "diurnal monsoon."

The classic monsoon climate, of which India is the best example, has a "hot season" prior to the onset of the rains. Though this does not occur every year in east central Florida (and hence is not climatological), the hottest temperatures of the season sometimes occur in May or June, prior to when rainfall frequency increases. In fact, the hottest month on record in Melbourne occurred in June 1998 when the area was in the midst of a prolonged dry spell. India also has a secondary maximum in temperature right after the Rainy Season. This does not occur in east central Florida since there is a strong marine influence, and temperatures are modified in September/October as the prevailing wind flow becomes more easterly.

In Trewartha (1968) the Kppen Climate Classification System designates north/central Florida as a Subtropical Humid climate (Cf) with a year-round distribution of rainfall. This places east central Florida in the same climate classification as Memphis, Tennessee! Clearly, Memphis and Melbourne should not have the same climate classification.

The Cw classification is a Subtropical Humid Wet-Dry climate with a monsoonal influence (dry winter). This classification requires the climatologically wettest month to have ten times more rainfall than the driest month. East central Florida does not meet this requirement since the driest month averages around 2 inches, and there is no location in the state which averages 20 inches in a month! An alternate to the 10:1 ratio is that 70% of the yearly rainfall must occur during the six warm season months. Rainfall for Daytona Beach during the months of May-October is about 64% of the yearly total, while Orlando and Melbourne were 68%, and Vero Beach was 66%.4

So it can be seen that east central Florida does not meet the strict definition of a Cw climate. However, during any given year, there is most always a month that is ten times wetter than another in east central Florida, since rainfall less than one inch is quite common during at least one of the Dry Season months. In fact, examination of Orlando rainfall from 1927-2001 showed that there were only 9 years when the 10:1 ratio was not met. This is the nature of statistics in which the average or "normal" conditions mask the extremes.

The Cs classification (Mediterranean Climate) occurs where there are dry summers and the wettest winter month has at least 3 times as much rain as the driest summer month. Trewartha states that in the Cf classification, the difference between the rainiest and driest months is less than for Cs. Yet, the climatologically wettest month in east central Florida has a little greater than 3 times the rainfall of the driest month.4 Therefore, east central Florida also does not meet the strict definition of a Cf climate.

The southern tip of Florida is an Aw (Tropical Wet-Dry) climate. The requirement for this designation is that the coolest month averages above 64.4 degrees Fahrenheit. East central Florida does not meet this requirement. However it is interesting to note that the rainfall requirements to receive a Tropical Wet-Dry designation are far less stringent when compared to the 10:1 ratio for the Cw (Subtropical Humid Wet-Dry) classification. The requirements are only that there must be a "marked seasonal rhythm" of rainfall and at least one month must have less than 2.4 inches. Both of these rainfall requirements are met for most of east central Florida.

A rainfall formula is used within the Tropical (A) classification to determine whether the climate is Monsoon (Am) or Wet-Dry (Aw). According to this formula, rainfall in east central Florida does not meet the Monsoon classification, but it does fit that of a Tropical Wet-Dry (Aw) climate. As noted above, rainfall requirements for Humid Subtropical Wet-Dry (Cw) are not achieved in east central Florida. Therefore, the Wet-Dry sub-categories of the A and C climate classifications appear to have a discrepancy with regard to the rainfall requirements.

So while it cannot be technically stated that this area has a Monsoon or a Wet-Dry climate, most years exhibit a monsoonal influence with distinct wet and dry seasons. The east central Florida climate fits more closely with the Cw classification than it does with Cf.

From HomePage

Fresh copy to be cached until 11:08:20 AM

Daily Fact

New Orleans has not been hit directly by a hurricane since 1965 when Hurricane Betsy blew in, flooding the city and killing about 75 people.

Source: Louisiana State Center