Disturbances 93L and 94L Little Threat; All-Time Record Heat in the Caribbean

An area of disturbed weather has developed along the boundary of a stalled cold front in the Western Gulf of Mexico's Bay of Campeche, and was designated Invest 94L by NHC on Sunday afternoon. Satellite loops show that 94L has a some respectable rotation and a moderate-sized region of heavy thunderstorms, but this activity was not well-organized. Long-range radar out of Brownsville, Texas showed heavy rain from 94L was affecting the Mexican coast, about 100 - 200 miles south of the Texas border. Wind shear was high, near 30 knots, and the 8 am EDT Sunday run of the SHIPS model predicted that wind shear would remain high, 20 - 30 knots, through Tuesday. These are marginal conditions for development, even though ocean temperatures are very warm--near 30°C (86°F). None of our reliable models for tropical cyclone genesis develop 94L, and they show little movement of the disturbance through Tuesday. In their 2 pm EDT Sunday Tropical Weather Outlook, NHC gave the wave 2-day and 5-day odds of development of 10% and 20%, respectively. The Hurricane Hunters are on call to investigate 94L on Monday, if needed.


Figure 1. Latest satellite image of 94L.

Invest 93L in the Central Atlantic may develop
A tropical wave located a few hundred miles southwest of the Cape Verde islands on Sunday morning was moving west to west-northwestwards at about 15 mph. The wave showed a modest increase in its heavy thunderstorm activity overnight, and was designated Invest 93L by NHC on Sunday morning. Conditions are favorable for development, with wind shear a moderate 10 - 20 knots, ocean temperatures at 28°C (83°F), and only a modest amount of dry air from the Saharan Air Layer lying to the north of the disturbance. The 8 am EDT Sunday run of the SHIPS model predicted that the wind shear over 93L through Thursday would be light to moderate, 5 - 15 knots, ocean temperatures would remain near 28°, and the atmosphere would remain relatively moist. Two of our three models for predicting tropical cyclone genesis, the UKMET and GFS models, forecasted in their 00Z Sunday runs that the wave would develop into a tropical depression midway between the Lesser Antilles Islands and Africa by Wednesday. In their 2 pm EDT Sunday Tropical Weather Outlook, NHC gave the wave 2-day and 5-day odds of development of 70% and 90%, respectively. It appears likely that this wave will curve to the north well before it can affect the Lesser Antilles Islands. The next name on the 2015 Atlantic list is "Ida".


Figure 2. Latest satellite image of 93L.

Elsewhere in the Atlantic: more fish storms
NHC is mentioning two other areas of interest in their Tropical Weather Outlook: an area of disturbed weather in the Central Atlantic about about 975 miles southwest of the Azores, far from any land areas, is being given 2-day and 5-day odds of development of 0%. A tropical wave emerged from the coast of Africa on Sunday. All three of our reliable models for predicting tropical cyclone genesis (UKMET, European, and GFS), in their 00Z Sunday runs, predicted that this wave would develop into a tropical depression midway between the Lesser Antilles Islands and Africa by Thursday. In their 2 pm EDT Sunday Tropical Weather Outlook, NHC gave the wave 2-day and 5-day odds of development of 0% and 20%, respectively. This wave will likely follow a path similar to 93L, turning northwards well before reaching the Lesser Antilles Islands. That is likely to be a common fate of tropical waves emerging from the coast of Africa during the remainder of September; we now have an active jet stream across the North Atlantic that is bringing frequent strong troughs of low pressure capable of recurving tropical disturbances to the north.

Remains of Grace bringing rain to the Caribbean
The remains of Tropical Storm Grace are bringing a few showers to Hispaniola and surrounding islands, but high wind shear will discourage any development. Grace's remains brought heavy rain and renewed flooding to the island of Dominica on Saturday, where 31 people died in floods due to Tropical Storm Erika in August. Radar-estimated rainfall amounts of up to 6" fell on the island from Grace's remains, according to the Antigua Met Service. Unfortunately, Grace's remains did little to alleviate the drought in Puerto Rico; San Juan picked up just a trace a rain on Saturday, and is still over 10" below the usual 34" of rain that they should have received by this point in the year.

All-time record heat in the Caribbean
Record heat scorched the Caribbean again on Saturday. According to weather records researcher Maximiliano Herrera, an all-time heat record was set on the island of Anguilla in the Lesser Antilles: 33.8°C (92.8°F), besting the record of 33.7°C set just four days previously. The Cuban capital of La Habana (Havana) also recorded its hottest temperature on record and the hottest temperature ever measured in September in Cuba, with 38.2°C (100.8°F) at the Casablanca Observatory. Havana's previous all-time heat record was set just a few months ago, on April 26, 2015: 37.0°C. According to an email I received from Cuban meteorologist Alejandro Adonis Herrera G., one of the instruments at the site recorded 38.1°C, but with maximum thermometer and technical corrections it was decided that the record is 38.2°C.


Figure 3. Temperature trace from the instrument at Havana's Casablanca Observatory on September 12, 2015. The station hit 38.2°C (100.8°F), the hottest temperature ever recorded in Havana. Image credit: Alejandro Adonis Herrera G.

Record heat and drought has been widespread over the Caribbean this summer, with the worst drought conditions occurring over Haiti, Eastern Cuba, Nicaragua, Panama, Colombia, Venezuela, Honduras, and Costa Rica. Reuters reported last month that Cuba began a two-month cloud-seeding campaign in September over the eastern part of the Caribbean island in hopes of easing its worst drought since at least 1901. The atmospheric circulation associated with the strong El Niño event in the Eastern Pacific has brought warm, sinking air and high pressure to the Caribbean, and has contributed to many cities recording their all-time highest temperatures on record. Another big factor in Saturday's record highs, and the record highs all across the Caribbean this year, is the fact that the year-to-date period of 2015 has been the warmest on record for the globe as a whole. Here is Mr. Herrera's list of cities in countries bordering the Caribbean that have set all-time heat records this year:

Cuba
Havana (Cuba), max. 38.1°C, September 12
Cienfuegos (Cuba) max. 37.0°C July 6
Jucaro (Cuba) max. 36.8°C July 10
Jucaro (Cuba) max. 37.0°C July 28
Contramaestre (Cuba) max. 38.2°C July 29
Isabel Rubio Airport (Cuba) max. 36.3°C July 29
Indio Hatuey (Cuba) max. 38.1°C July 30
Holguin (Cuba), max. 38.7°C, April 26
Guaro (Cuba), max. 38.0°C, April 26
Contramaestre (Cuba), max. 37.7°C, April 27
Velasco (Cuba), max. 38.6°C, April 28
Ciego de Avila (Cuba), max. 38.0°C, April 28
Puerto Padre (Cuba), max. 38.4°C, April 29
Punta Lucrecia (Cuba), max. 37.3°C, April 29
Nuevitas (Cuba), max. 38.5°C, April 30

Colombia
Riohacha (Colombia) max. 40.6°C July 13
Cartagena, Colombia, max. 40.4°C, June 24
Santa Marta, Colombia, max, 38.6°C, June 24
Arjona, Colombia, max, 40°C, June 24
Urumitia, Colombia, max, 42.0°C, June 27
Riohacha, Colombia, max, 40.0°C, June 29

Mexico
Merida (Mexico), max. 43.6°C, April 26

Honduras
Tela (Honduras), max. 40.6°C, April 28

Venezuela
Coro (Venezuela), max. 43.6°C, April 29 (New all-time national record high for Venezuela)

Dominican Republic
Santo Domingo (Dominican Republic), 37.2°C, August 27

U.S. Virgin Islands
Charlotte Amalie (U.S. VI), 35.6°C (96°F), September 10 (all time high for the station and the U.S. Virgin Islands)

Jeff Masters