Thousands Dead in Wake of Storm Daniel in Libya

Posted on September 14, 2023 by Fred Pickhardt

Satellite Image of Storm Daniel moving acorss Libya

A storm system that moved southeast from the Mediterranean Sea across Libya caused heavy rains which burst two dams which set-off a 7 meter (23 ft) wall of water which destroyed large parts of Derna, Liby this past weekend. The disaster was caused, in part, by old and crumbling infrastructure as much as the storm itself.  As of Thursday it was estimated that the flooding killed at least 8,000 people and the eastern Libyan city of Derna was the worst hit where there remains at least 10,000 still missing according to local officials.  The two dams that burst on Monday were built around half a century ago, between 1973 and 1977.

The extreme rainfall on Sunday was brought by a system called “Daniel” which swept southeastward from the Mediterranean had subtropical characteristics and has been referred to as a “Medicane”.  Daniel dumped more than 16 inches (414 mm) of rainfall in 24 hours to Al-Bayda, a city west of Derna. Derna has been prone to flooding in the past with at least five deadly floods since 1942. The most recent occurred in 2011.

Before and After Image of Flooding in Derma

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The lack of any warnings added to the disaster as there was no operating weather service that could have issued warnings

Ocean Weather Services

 

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Hurricane Lee Weakens as it moves Northward

Posted on September 14, 2023 by Fred Pickhardt

Hurricane Lee Update: Sept.14th 1100 EDT:

Hurricane Lee over the Western North Atlantic

Hurricane Lee has weakened to max winds of 80 kts with a min pressure of 956 mb with significant wave heights up 14 meters (46 feet).  Hurricane force winds extend outward 80 nm NE and 70 nm to the West.  50 kt winds extend outward 140 nm NE and 110 nm SW. 

 

 

 

 

Lee is moving N to NNE at 12 kts, however, a slight turn towards the NNW is expected late Friday or early Saturday.   Thereafter, Lee is forecast to turn towards the NE over Atlantic Canada.

NOAA WPC Wave Height Analysis

 

Gradual weakening is forecast during the next 36 hours due to increasing wind shear and will transition into an extratropical storm low by 48 hours. Tropical storm conditions, heavy rainfall, and high surf will continue to impact Bermuda through Friday morning, and a Tropical Storm Warning is in effect for the island.

 A Hurricane Watch is in effect for portions of eastern Maine, southern New Brunswick, and western Nova Scotia on Saturday.  A tropical storm warning is in effect for Cape Cod, Martha’s Vineyard, and Nantucket .

Heavy rainfall from Lee may produce localized urban and small stream flooding across eastern New England and into portions of New Brunswick and Nova Scotia from Friday night into Saturday night.

There is the potential for life-threatening storm surge flooding in portions of southeastern Massachusetts, including Cape Cod and Nantucket, late Friday and Saturday, where a Storm Surge Watch is in effect.

Risk for Tropical Storm Force winds 34 kts (39 mph)

Currently, the risk for encountering winds of 34 kts (39 mph) are less than 10 % for Boston, 20-25% for Nantucket, 20% for Cape Cod, 50-55% for Eastport, and 50-60% for St. John NB.

Latest NOAA NHC Advisory

Fred Pickhardt
Ocean Weather Services

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Hurricane Lee making its Turn towards the North

Posted on September 13, 2023 by Fred Pickhardt

NOAA NHC Forecast Track

Update: Hurricane Lee at 11am EDT was located near 26.4N  67.2W, moving NNW at 8 kts with max winds 100 knots (115 mph).  Significant wave heights currently to 13-14 meters (42-46 feet).  Hurricane force winds extend outward 100 nm to the NE and 60 nm to the SE.  50 knot (58 mph) winds extend out 130 nm to the NE and 90 nm to the SW.

Lee is now making its turn towards the north which will take the core of the system to the west of Bermuda Thursday and Thursday night. Lee will be moving over cooler sea temperatures which will weaken the system. The forecast track brings Lee close to southeastern New England before reaching Maine and Atlantic Canada later in the weekend.

Tropical storm conditions, heavy rainfall, and high surf are expected to impact Bermuda beginning early Thursday, and a Tropical Storm Warning is in effect for the island. There is an increasing risk of wind, coastal flooding, and rain impacts from Lee in portions of New England and Atlantic Canada beginning on Friday and continuing through the weekend.

Currently the risk for gale force winds (34 kt/39 mph) for Boston is about 20% and at Nantucket  and Cape Cod,about 40-50%.

Risk for winds at least 34 knots

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Hurricane Lee to pass west of Bermuda

Posted on September 12, 2023 by Fred Pickhardt

NOAA Visible Satellite Hurricane Lee

Hurricane Lee 1100 AM EDT Tue Sep 12 2023

Hurricane Lee is moving WNW at 5 kts with max winds of about 100 kts (115 mph), max significant wave height estimated about 12 meters (40 feet), and a minimum pressure of 951 mb.  Hurricane force winds extend outward about 80 nm to the northeast and 50 nm to the southwest.

Hurricane Lee Wind Field

 

 

Heavy swell from Lee will cause dangerous surf and life-threatening rip currents will affect portions of the northern Leeward Islands, the Virgin Islands, Puerto Rico, Hispaniola, the Turks and Caicos Islands, the Bahamas, Bermuda, and most of the U.S East Coast through much of the week.

The officeal NHC Forecast Track shows Lee turning NW then startarting to accelerate towards the north during the next couple of days.  The core of Lee is forecast to pass west of Bermuda bringing some wind impacts to the island on Thursday and a Tropical Storm Watch has been issued for the island. 

 

After about 24 hours, Lee will encounter cooler sea surface temperatures which should gradually weaken the system late Wednesday and Thursday.

Once Lee passes north of the Gulf stream Friday and Saturday, significantly colder sea temperatures will cause more rapid weakening and start a transition into an extratropical storm low as it passes north of Georges Bank and approaches Nova Scotia or the northeastern coast of Maine. 

There is a risk for a period of 30-45 kt winds over portions of Cape Cod and Nantucket late Friday night and Saturday.

Sea Surface Temperature (F)

 

 

Latest NOAA NHC Advisory

Fred Pickhardt

 

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Hurricane Lee Regaining Strength

Posted on September 10, 2023 by Fred Pickhardt

Hurricane Lee IR Satellite

Hurricane Lee has become better organized today and has regained 105 kt max winds by late this afternoon with an eye diameter of 20 nm and min pressure of 954 mb. Lee continues WNW at 7 kts with hurricane force winds extending outward 35-40 nm east of the center and 30-40 nm to the west. Storm force (50 kt or more) winds extend out 50 nm to the SW and up to 90 nm to the NE. Max significant wave heights about 36 feet (11 meters).

Lee is expected to restrengthen during the next 24-36 hours and is expected regain category 4 status tonight or early Monday. Thereafter, slow weakening is likely with somewhat more rapid weakening expected once Lee moves over cooler sea temperatures north of about 25 N latitude.

Sea Surface Temperatures Sept. 10, 2023

Heavy swell from Lee will cause dangerous surf and life-threatening rip currents will affect portions of the northern Leeward Islands, the Virgin Islands, Puerto Rico, Hispaniola, the Turks and Caicos Islands, the Bahamas, and Bermuda through much of this week.

Wave Direction and Height

Lee is forecast to turn more towards the northwest in about 48 hours then turning more towards the North.

NHC Forecast Track

 

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Why is it so warm in the North Atlantic?

Posted on June 24, 2023 by Fred Pickhardt

Sea Surface Temperatue North Atlantic

The overall recent warming of the North Atlantic, particularly in the northeastern sector and the Atlantic Main Tropical Cyclone Development Region may be, in large part, due a combination of the Atlantic Multi-decadal Oscillation (AMO) being in its warm phase which raises the base sea surface temperatures in the North Atlantic and  warming resulting from the recent reduced trade winds in the tropics.

June 2023 North Atlantic surface pressure anomaly

Strong Warm AMO Pattern

Strong Warm AMO Pattern

Sea surface temperature (SST) anomalies in the Tropical North Atlantic have been increasing since April due mainly to a weakening and southward displacement of the Azores-Bermuda ridge. This weakening has reduced the trade winds.

 

 

The dominant cause of the warm SSTs  is due to weather patterns that reduced surface wind speed, which reduced evaporative cooling, and less cloudiness. 

Other factors include CO2 emissions, lower amount of sulfate particles from cleaner shipping fuels, Hunga-Tonga eruption, and low levels of African dust.

Since late June, the Azores-Bermuda ridge has begun to restrengthen somewhat and SSTs have fallen, however, they remain warmer than normal. 

Sea Surface Temperature for the Atlantic Main Development Region

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How’s the Weather Cruising the Caribbean and Gulf of Mexico during July?

Posted on June 6, 2023 by Fred Pickhardt
Gulf of Mexico and Caribbean Sea

Pilot Chart Gulf of Mexico and Caribbean Sea July

Wind

Caribbean Sea
Easterly winds mostly Beaufort force 4 (11-16 knots) prevail this month, except forces 4-5 (11-21 knots) prevail over the central Caribbean north of Columbia. Over the southwestern Caribbean the wind will back east to northeast and diminish to forces 3-4 (7-16 knots) and over the northwestern Caribbean, winds tend to be from the east forces 3-4 (7-16 knots).  There is a low (about 1%) risk for encountering gale forces 8-9 (34-47 knots) over the central Caribbean north of the Columbian coast during July. 

Gulf of Mexico
East to southeast winds, mostly forces 3-4 (7-16 knots) prevail, except becoming more variable in direction forces 2-3 (4-12 knots) over the Northeast Gulf and southeast to south forces 3-4 (7-16 knots) over the Northwest Gulf. 

Waves
Generally waves average 2-5 feet (0.5-1.5 meters), however, over the Central Caribbean 6-8 foot (2-2.5 meter) waves will prevail. The risk for rough seas of 8 feet (2.4 meters) or higher is less than 10% across the Gulf of Mexico, the northwestern and the easternmost Caribbean, however, the risk increases to 30-45% over the central Caribbean Sea, especially north of Columbia. 

Temperature
Over the Gulf of Mexico air temperatures average around 82-84 F (28-29 C) over the Gulf of Mexico and 81-83 F (27-28.5 C) across the Caribbean. 

Land Temperature
Overall, most Caribbean destinations see morning lows of 74-80 F (23-27 C) during July with daytime highs mostly 86-92 F (30-33 C). The hottest locations are Aruba, Cancun, Cozumel and the Caymans with afternoon high temperatures averaging at or above 90 F (32 C). 

Tropical Cyclones
The risk for tropical cyclones increases gradually during July with the highest risk area located in the north-central Gulf of Mexico.

Tropical Cyclone Frequency

July Pilot Chart Tropical Cyclone Frequenc

 

Rainfall
Rainfall during July varies quite a bit from 1.2 inches in Aruba to about 9.6 inches in Belize. The wettest locations include Belize, Bahamas, Trinidad, Dominica, St. Lucia and Martinique.  Drier locations include Aruba and Curacao, Cancun, Montego. St. Maarten, and St. Thomas.  

Fred Pickhardt
Ocean Weather Services

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Carnival Sunshine runs into large waves returning from Bahamas

Posted on May 29, 2023 by Fred Pickhardt

The cruise ship Carnival Sunshine ran into some large waves churned up by a storm off the Southeast coast delaying its return from the Bahamas over the Memorial Day weekend.

NOAA WPC Surface Analysis

A low pressure system off the southeast US coast combined with strong high pressure to the north produced winds to 50 knots building seas to 24 feet (7.3 meters) north and west of the center.

 

NOAA ACCAT (Satellite derived winds)

Some of the strongest winds occured over the Gulf Stream and counter to the flow of the current. When ocean wind or swell waves encounter a current moving in the opposite direction, the response will be for wave speed and length to decrease, wave period will not change, but wave heights will increase, resulting in taller, steeper waves. In some cases, this can even lead to waves breaking, resulting in greater energy against vessel hulls.

Read more about high wind and wave events crossing the Gulf Stream

Ocean Weather Services 

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Floods in Italy force thousands of people to leave their homes

Posted on May 24, 2023 by Fred Pickhardt

Intense rainfall over northern Italy May 16, 2023

Intense rainfall in mid-May resulted in severe flooding in the northern Italian region of Emilia-Romagna displacing over 30,000 people and killing 14.  Six months’ worth of rain was reported in about 36 hours from 16 May resulting in over 300 landslides and flooding of many fields and roads.

 

 

 

The cause of the excessive rainfall was a vigorous cut-off upper-level low over the Tyrrhenian Sea which allowed a strong jet to funnel moisture from the Mediterranean Sea northward over the Adriatic Sea and into northern Italy where intense rains fell, particularly over the Emilia Romagna region.

500 mb jet via https://www.ventusky.com/

Whether any of this can be attributed to climate change is highly uncertain. 

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Record Rainfall in Fort Lauderdale

Posted on May 6, 2023 by Fred Pickhardt

NOAA NWS Rainfall Estimate

Reord rainfall in Fort Lauderdale. A stationary supercell thunderstorm that centered itself near Fort Lauderdale, Florida produced prolonged periods of 3+ inch hourly rainfalls creating widespread flooding. The heaviest rainfall, in excess of 20 inches, appears to have occurred from Ft. Lauderdale to Hollywood. It has been estimated that up to 1.5 inches of rain fell in 10 minutes in Fort Lauderdale!

Early on the morning of April 12th, there was a weak 1010 mb low over the central Gulf of Mexico with a slow moving warm front extending eastward to the Florida Keys. Over the northeastern Gulf surface winds were 25-35 kts from the east.

NOAA NWS Surface Analysis 1200 UTC 12 April 2023

Higher-up in the atmosphere there was a cut-off 500 mb low centered over southeastern Louisiana which was causing a strong wind flow from the WSW across South Florida. At the surface  a long fetch of moderate to fresh moist ENE winds prevailed along the southeastern coast of Florida to the north of the warm front.  

NOAA NWS 500 MB ANALYSIS

By mid-afternoon, the low was drifting slowly northward while the associated warm front had moved north of the Keys but was still located to the south of the Miami area. The intersection of the warm front, the strong upper-level WSW winds over moderate to fresh moist ENE winds at the surface created strong vertical wind shear with high moisture levels in the low and mid levels, an ideal environment for heavy convective showers and thunderstorms. 

NOAA NWS Surface Analysis 1800 UTC 12 April 2023

 

 

 

 

 

 

 

 

 

 

 

 

A cluster of nearly stationary heavy thunderstorms developed along the Southeast Coast of Florida with the heaviest activity from Fort Lauderdale to Holiday. The combination of impervious surfaces of a highly urbanized area with extreme rainfall rates caused severe surface rainfall runoff which resulted in enhanced street flooding and flooding of airport runways. 

Whether or not the rainfall amount was enhanced by climate change is debateable, however, the effects of urbanization are likely the main reason for the overall impact of the flooding. 

 

Fred Pickhardt

 

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