Mariners Weather Log Vol. 60, No. 2, August 2016

Tropical Atlantic and Tropical East Pacific Areas September through December 2015

Marshall Huffman and Andy Latto
Tropical Analysis and Forecast Branch
National Hurricane Center, Miami, Florida
NOAA National Centers for Environmental Prediction

Tropical North Atlantic Ocean to 31N and Eastward to 35W, including the Caribbean Sea and the Gulf of Mexico

Atlantic Highlights

The TAFB Atlantic High Seas area of responsibility (AOR) extends from 7°N to 31°N west of 35°W, including the Caribbean Sea and Gulf of Mexico. Forty eight gale warnings were issued for this area from January through April 2016; with four storm force wind warnings and no hurricane force wind warnings issued during the period. The 48 warnings issued in the Atlantic basin was the second highest number of warnings ever issued by TAFB during a winter season, following the record breaking winter season of 2015 with 54 warnings. The number of warnings was up from the January through April five year average of 31 warnings. Of the 48 warnings issued, 15 of these were located in the Gulf of Mexico, 13 of these were located in the Atlantic Ocean, and 20 were located in the Caribbean Sea.

Table 1. Non-tropical warnings issued for the Atlantic Ocean between 01 January 2016 and 30 April 2016. Storm events are shaded and the duration of the storm warning is in parentheses.

Onset	Region	Peak Wind	Gale Duration (Storm)	Forcing
01 Jan 0000 UTC	Caribbean	35 kts	24h	Pressure Gradient
01 Jan 1800 UTC	Gulf of Mexico	40 kts	24h	Cold Front
03 Jan 0000 UTC	Gulf of Mexico	35 kts	06h	Cold Front
03 Jan 1800 UTC	Gulf of Mexico	35 kts	06h	Cold Front
06 Jan 1200 UTC	SW North Atlantic	55 kts	66h (12h)	Cold Front
10 Jan 0600 UTC	SW North Atlantic	50 kts	78h (12h)	Cold Front
15 Jan 0600 UTC	Gulf of Mexico	35 kts	12h	Pressure Gradient
15 Jan 1200 UTC	SW North Atlantic	40 kts	36h	Pressure Gradient
17 Jan 0000 UTC	Gulf of Mexico	50 kts	18h (12h)	Cold Front
17 Jan 1200 UTC	SW North Atlantic	40 kts	24h	Pressure Gradient
22 Jan 0600 UTC	Gulf of Mexico	40 kts	42h	Cold Front
22 Jan 1800 UTC	SW North Atlantic	35 kts	66h	Cold Front
26 Jan 0600 UTC	Caribbean	35 kts	12h	Pressure Gradient
27 Jan 0600 UTC	Caribbean	35 kts	12h	Pressure Gradient
27 Jan 0600 UTC	Gulf of Mexico	35 kts	42h	Cold Front
29 Jan 0600 UTC	SW North Atlantic	40 kts	30h	Cold Front
04 Feb 0000 UTC	Gulf of Mexico	35 kts	06h	Cold Front
04 Feb 1800 UTC	Gulf of Mexico	35 kts	12h	Cold Front
07 Feb 1200 UTC	SW North Atlantic	50 kts	36h (12h)	Cold Front
08 Feb 1800 UTC	Gulf of Mexico	35 kts	36h	Cold Front
09 Feb 0000 UTC	SW North Atlantic	35 kts	42h	Cold Front
11 Feb 0600 UTC	Caribbean	35 kts	12h	Pressure Gradient
12 Feb 0600 UTC	Caribbean	35 kts	12h	Pressure Gradient
15 Feb 0600 UTC	Caribbean	35 kts	12h	Pressure Gradient
16 Feb 0600 UTC	SW North Atlantic	35 kts	12h	Cold Front
19 Feb 0600 UTC	Caribbean	35 kts	12h	Pressure Gradient
20 Feb 0600 UTC	Caribbean	35 kts	12h	Pressure Gradient
21 Feb 0600 UTC	Caribbean	35 kts	12h	Pressure Gradient
23 Feb 1800 UTC	Gulf of Mexico	35 kts	30h	Cold Front
04 Mar 1200 UTC	SW North Atlantic	35 kts	06h	Cold Front
07 Mar 1800 UTC	SW North Atlantic	40 kts	24h	Cold Front
09 Mar 0600 UTC	Gulf of Mexico	35 kts	36h	Cold Front
10 Mar 0000 UTC	Caribbean	35 kts	36h	Pressure Gradient
11 Mar 1800 UTC	Caribbean	35 kts	18h	Pressure Gradient
20 Mar 0000 UTC	Gulf of Mexico	40 kts	30h	Cold Front
23 Mar 0000 UTC	Caribbean	35 kts	12h	Pressure Gradient
24 Mar 0000 UTC	Caribbean	35 kts	06h	Pressure Gradient
25 Mar 0000 UTC	Caribbean	35 kts	12h	Pressure Gradient
26 Mar 0000 UTC	Caribbean	35 kts	12h	Pressure Gradient
27 Mar 0600 UTC	Caribbean	35 kts	06h	Pressure Gradient
28 Mar 0000 UTC	Caribbean	35 kts	12h	Pressure Gradient
31 Mar 0600 UTC	Gulf of Mexico	40 kts	06h	Pressure Gradient
02 Apr 0600 UTC	Gulf of Mexico	40 kts	18h	Cold Front
09 Apr 0600 UTC	Caribbean	35 kts	06h	Pressure Gradient
10 Apr 0600 UTC	Caribbean	35 kts	06h	Pressure Gradient
11 Apr 0600 UTC	Caribbean	35 kts	06h	Pressure Gradient
20 Apr 0600 UTC	SW North Atlantic	35 kts	12h	Cold Front
25 Apr 1200 UTC	SW North Atlantic	40 kts	24h	Pressure Gradient

Table 1 details the warnings issued in the TAFB Atlantic High Seas AOR from January through April 2016. The strongest wind event this winter season was a storm force event that occurred in the southwest North Atlantic region that materialized as a weak 1012 hPa low pressure area on 06 January at 1800 UTC across the northwestern Bahamas. The low went through a period of rapidintensification, deepening to 987 hPa, a drop of more than 1 hPa an hour within a 24 hour Figure 2. A RapidScat pass valid around 1738 UTC 07 January. Note the dark blue and pink wind barbs in the southwest North Atlantic indicating gale force winds between 34 kts and 49 kts and the purple wind barbs indicating storm force winds between 50 kts and 63 kts. period by 07 January at 1800 UTC. The result of this rapid deepening generated gale force conditions for almost three days beginning 06 January at 1200 UTC in the vicinity of the low center. A brief 12 hour period of storm force winds occurrednear the low center with Figure 1 showing a MetOp AdvancedxxSCATerometer (ASCAT-B) pass from 07 January. Note the blue and pink wind barbs indicating 34-49 kts gale force winds and purple wind barbs indicating 50-63 kts storm force winds in the southwest North Atlantic that reached the surface. Warnings were discontinued across the region by 0600 UTC 09 January.

Figure 2 shows a RapidScat pass several hours later on 07 January indicating the storm force winds within the southwestern quadrant of the low. The RapidScat instrument is currently a scatterometer onboard the International Space Station (ISS).

During this storm force wind event, several ships reported gale or storm force conditions and these are summarized in Table 2.

Table 2. Ship observations during the gale warning period beginning 06 January 1200 UTC and ending 09 January 0600 UTC.

Ship	Call Sign	Wind Speed	Location	Date/Time
Carnival Fantasy	H3GS	40 kts	23.5N 80.0W	06 Jan 1200 UTC
Carnival Fascination	C6FM9	35 kts	26.5N 79.3W	06 Jan 1200 UTC
Celebrity Eclipse	9HXC9	39 kts	25.6N 77.5W	06 Jan 2300 UTC
COSCO Germany	CQGT	45 kts	28.4N 74.3W	07 Jan 1200 UTC

The longest duration gale force wind event for the Caribbean Sea was 36 hours in length and formed due to a strong pressure gradient set up between a relatively strong high pressure system anchored across the southwest North Atlantic Ocean and lower pressure across the northwestern South American continent. Gale force conditions persisted for a day and a half before a frontal trough across the southeastern United States weakened the southwest North Atlantic ridging and relaxed the pressure gradient across the Caribbean Sea. Figure 3 shows a MetOp Advanced SCATerometer (ASCAT-B) pass from 10 March.

Note the blue wind barbs indicating 34 to 40 kts winds in the southwestern Caribbean Sea near the coast of Colombia that reached the surface. In addition, the red wind barbs indicate near gale force winds, 28 to 33 kts winds extending 120 nmi off the northern coast of Colombia. Figure 4 shows a RapidScat pass more than 24 hours later early on 11 March indicating the extent of near gale to gale force winds continuing across a large portion of the southwest Caribbean Sea. Warnings were discontinued in the Caribbean Sea by 1200 UTC 11 March.

The strongest and longest duration Gulf of Mexico warning was a gale force warning that occurred across the basin in the four month period. This gale force warning began at 0600 UTC 22 January and persisted for 42 hours. A strong surface pressure gradient materialized across the Gulf of Mexico waters after the passage of a strong cold front. Table 3 summarizes ships that reported winds of gale force or greater west of the cold front. The following two figures, Figure 5 and Figure 6, are RapidScat passes valid during the warning period time showing brown and red wind barbs which indicate near gale to gale force conditions.

Table 3. Ship observations during the gale warning period beginning 22 January 0600 UTC and ending 24 January 0000 UTC.

Ship	Call Sign	Wind Speed	Location	Date/Time
Discoverer Deep Seas	V7HC6	38 kts	28.7N 90.0W	22 Jan 0600 UTC
Overseas Anacortes	KCHV	40 kts	28.7N 88.0W	22 Jan 0600 UTC
Pacific Sharav	D5DY4	44 kts	27.1N 91.2W	22 Jan 0700 UTC
Maersk Carolina	WBDS	37 kts	26.6N 89.2W	22 Jan 1200 UTC
Maersk Carolina	WBDS	35 kts	27.3N 91.1W	22 Jan 1800 UTC
Norwegian Jade	C6WK7	36 kts	28.2N 92.9W	23 Jan 0000 UTC
Brasil Voyager	C6ZJ8	38 kts	29.1N 87.1W	23 Jan 0000 UTC
Caribbean Princess	ZCDG8	45 kts	24.2N 88.6W	23 Jan 0000 UTC
Carnival Dream	3ETA7	35 kts	22.5N 85.7W	23 Jan 0100 UTC
Asia Vision	C6AX3	40 kts	23.9N 84.1W	23 Jan 0300 UTC
Norwegian Dawn	C6FT7	40 kts	22.1N 86.5W	23 Jan 0700 UTC
Seabulk Trader	KNJK	45 kts	26.8N 89.9W	23 Jan 1000 UTC
Norwegian Star	C6FR3	43 kts	23.6N 86.0W	23 Jan 1200 UTC
Regal Princess	ZCEK6	40 kts	23.7N 81.8W	23 Jan 2000 UTC

Tropical Eastern North Pacific Ocean to 30N and East of 140W

Pacific Highlights

There were 25 gale or stronger events in the North Pacific east of 140W between 30N and the equator from 01 January 2016 to 30 April 2016 (Table P-A). Of these events, 11 occurred over the gulf of Tehuantepec, 4 over the Gulf of Papagayo, 5 over the open waters of the Pacific N of 27N, 4 over the Gulf of California, and 1 over the tropical Pacific. Four of the events over the Gulf of Tehuantepec reached Storm Force of 50 kts or greater with nine events over this portion of the Pacific persisting 36 hours or longer at gale force.

February 5 Gulf of California Gale:

There were several Gulf of California Gale events during the first four months of 2016. These gale events can occur from a variety of pressure forcing schemes. Gale events February 1 and again March 8 occurred due to a strong cold front passing across the region. A different setup forced the gale event on February 5. Figure 1, a trough of low pressure developed over western Mexico to the east of the Gulf of California, while a very strong 1042 hPa high pressure builds southeastward over the Great Basin. This particular event was not directly from a frontal passage, but rather from the tight pressure gradient that established itself across the region. Figure 2, a Strong to gale-force north-northwest winds extend across the entire length of the Gulf of California. This particular event lasted only 12 hours, as the diurnally driven trough dissipated. By the time the trough redeveloped the next day, the strong high to the north had shifted to the east.

Table P-A lists the Gale or greater events over the northern Pacific east of 140 W between 30 N and the Equator.

Onset	Region	Peak Wind Speed	GALE/STORM Duration	Forcing
0430 UTC 01 Jan	Gulf of Tehuantepec	40 kts	108 hr	Gap
0430 UTC 03 Jan	Eastern Pacific 27N	35 kts	12 hr	Front
1630 UTC 10 Jan	Eastern Pacific 28N	35 kts	06 hr	Front
1630 UTC 10 Jan	Gulf of Tehuantepec	40 kts	24 hr	Gap
0430 UTC 13 Jan	Gulf of Tehuantepec	35 kts	12 hr	Gap
1630 UTC 17 Jan	Gulf of Tehuantepec	50 kts	72 hr / 6hr	Gap
1030 UTC 19 Jan	Gulf of Papagayo	35 kts	30 hr	Gap
1630 UTC 22 Jan	Gulf of Tehuantepec	50 kts	54 hr / 24hr	Gap
1030 UTC 24 Jan	Gulf of Papagayo	35 kts	36 hr	Gap
1030 UTC 28 Jan	Gulf of Tehuantepec	40 kts	36 hr	Gap
1030 UTC 01 Feb	Gulf of California	35 kts	18 hr	Front
1030 UTC 04 Feb	Gulf of Tehuantepec	50 kts	252 hr / 30hr	Gap
0430 UTC 05 Feb	Gulf of California	35 kts	18 hr	Front
1630 UTC 07 Feb	Gulf of Papagayo	40 kts	126 hr	Gap
0430 UTC 14 Feb	Eastern Pacific 13N	40 kts	36 hr	Trough
0430 UTC 17 Feb	Gulf of Tehuantepec	45 kts	84 hr	Gap
1030 UTC 19 Feb	Gulf of Papagayo	35 kts	36 hr	Gap
0430 UTC 23 Feb	Eastern Pacific 29N	35 kts	06 hr	Front
2230 UTC 24 Feb	Gulf of Tehuantepec	55 kts	96 hr/ 12 hr	Gap
1030 UTC 08 Mar	Eastern Pacific 29N	35 kts	12 hr	Front
1030 UTC 08 Mar	Gulf of California	35 kts	12 hr	Front
2230 UTC 10 Mar	Eastern Pacific 27N	35 kts	12 hr	Front
2230 UTC 20 Mar	Gulf of Tehuantepec	45 kts	54 hr	Gap
1030 UTC 29 Mar	Gulf of California	35 kts	12 hr	Front
0430 UTC 03 Apr	Gulf of Tehuantepec	40 kts	114 hr	Gap

Gulf of Tehuantepec Gale and Storm Warnings:

The Gulf of Tehuantepec wind events are usually driven by mid-latitude cold frontal passages through the narrow Chivela Pass in the Isthmus of Tehuantepec between the Sierra Madre de Oaxaca Mountains on the west and the Sierra Madre de Chiapas Mountains on the east. The northerly winds from the southwest Gulf of Mexico funnel through the pass delivering stronger winds into the Gulf of Tehuantepec. The 906 hours of duration of gale force or higher warnings in the January through April 2016 period for the Gulf of Tehuantepec nearly matched the 936 hours during the same period in 2015, and was 45% greater than the 627 hours in 2014. The 72 hours of storm warnings for this period in 2016 exceeded the 60 hours of storm warnings for this same period in 2015.

The longest duration gale/storm event that occurred during the January to April 2016 time period began 1030 UTC February 4 with long duration gale force winds lasting until 2230 UTC February 14 (a total of 252 hours). Storm-force winds developed during two different time periods during this long duration gale, (from 0430 UTC-2230 UTC February 5, and from 1030 UTC- 2230 UTC February 7) totaling 30 hours. The same high pressure ridge that forced the February 1 Gulf of California event eventually helped to force this Tehuantepec event. Also, the classic setup for driving a Tehuantepec event was indicated in computer model forecasts and Gale warnings were hoisted 24 hours in advance of the event while the strong cold front crossed northeastern Mexico. (Figure 3) Severe gale winds are occurring over the Gulf of Tehuantepec north of 15N along 95W. (Figure 4) Gale conditions were already underway over the Gulf of Tehuantepec while a reinforcing Gulf of Mexico cold front pushed across the coast of southern Mexico. A strong 1029 hPa high over southern Texas behind the front forced the Tehuantepec gap winds to increase to storm force over the subsequent 12 hours.

Five Day Papagayo Gale:

The Gulf of Papagayo gap wind events are usually driven by strong Caribbean Sea trade winds that traverse the San Juan River valley and the southern portion of Lake Nicaragua to the Pacific Ocean. Winds in the Gulf of Papagayo during these events are usually less than gale force. On rare occasions a strong cold front reaches the coast of southern Nicaragua and funnels stronger winds through the gap. The winds are further enhanced by nocturnal and early morning drainage flow. The same strong high pressure that forced the long duration early February Tehuantepec event built southeastward over the Gulf of Mexico February 4 and was reinforced on February 8 as a series of cold fronts swept across the Gulf of Mexico and western Caribbean. The strength of the first high forced a cold front unusually far south into the southwestern Caribbean on February 6 and 7, initiating this gap wind event. The second high helped to reinforce the tight pressure gradient across the region (Figure 5). A cold front has already passed southeast of Nicaragua and has stalled out over the southwestern Caribbean to Panama. (Figure 6) Winds to gale-force extend from the Gulf of Papagayo as far west as 88W between 10.5N and 11.5N. The ISLAND PRINCESS (ZCDG4) also reported gale force winds on 11 February 2016 while passing by the Gulf of Papagayo.

Valentine's Day Tropical Pacific Gale Event:

A broad upper level low over the tropical eastern Pacific began to translate to the surface in the form of a surface trough on February 1 near 06N132W to 14N128W. Intensifying high pressure to the north of the trough tightened the pressure gradient on both sides of trough. This gradient supported a broad area of winds to 30 kts, locally to gale force of 40 kts, beginning 0430 UTC February 14, 2016 and persisting for 36 hours. (Figure 7) A large area of cloud cover imagery produced by the combination of the upper level trough and surface trough over the region was evident in visible satellite imagery. (Figure 8) An area of 25 kts to 35 kts winds are verified from 08N to 19N between 128W and 136W around the surface trough. Combined seas to 18 ft were occurring at the end of a long fetch of winds nearing gale force.

The trough would remain quasistationary through February 15. However, with the high to the north of the area weakening, the pressure gradient loosened and winds diminished below galeforce.